CWE - VIEW SLICE: CWE-1178: Weaknesses Addressed by the SEI CERT Perl Coding Standard (4.14)

CWE VIEW: Weaknesses Addressed by the SEI CERT Perl Coding Standard

View ID: 1178

Vulnerability Mapping: PROHIBITEDThis CWE ID must not be used to map to real-world vulnerabilities
Type: Graph

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Objective

CWE entries in this view (graph) are fully or partially eliminated by following the guidance presented in the online wiki that reflects that current rules and recommendations of the SEI CERT Perl Coding Standard.

Audience

Stakeholder	Description
Software Developers	By following the SEI CERT Perl Coding Standard, developers will be able to fully or partially prevent the weaknesses that are identified in this view. In addition, developers can use a CWE coverage graph to determine which weaknesses are not directly addressed by the standard, which will help identify and resolve remaining gaps in training, tool acquisition, or other approaches for reducing weaknesses.
Product Customers	If a software developer claims to be following the SEI CERT Perl Coding Standard, then customers can search for the weaknesses in this view in order to formulate independent evidence of that claim.
Educators	Educators can use this view in multiple ways. For example, if there is a focus on teaching weaknesses, the educator could link them to the relevant Secure Coding Standard.

Relationships

The following graph shows the tree-like relationships between weaknesses that exist at different levels of abstraction. At the highest level, categories and pillars exist to group weaknesses. Categories (which are not technically weaknesses) are special CWE entries used to group weaknesses that share a common characteristic. Pillars are weaknesses that are described in the most abstract fashion. Below these top-level entries are weaknesses are varying levels of abstraction. Classes are still very abstract, typically independent of any specific language or technology. Base level weaknesses are used to present a more specific type of weakness. A variant is a weakness that is described at a very low level of detail, typically limited to a specific language or technology. A chain is a set of weaknesses that must be reachable consecutively in order to produce an exploitable vulnerability. While a composite is a set of weaknesses that must all be present simultaneously in order to produce an exploitable vulnerability.

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1178 - Weaknesses Addressed by the SEI CERT Perl Coding Standard

Category - a CWE entry that contains a set of other entries that share a common characteristic.SEI CERT Perl Coding Standard - Guidelines 01. Input Validation and Data Sanitization (IDS) - (1179)

1178 (Weaknesses Addressed by the SEI CERT Perl Coding Standard) > 1179 (SEI CERT Perl Coding Standard - Guidelines 01. Input Validation and Data Sanitization (IDS))

Weaknesses in this category are related to the rules and recommendations in the Input Validation and Data Sanitization (IDS) section of the SEI CERT Perl Coding Standard.

Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') - (22)

1178 (Weaknesses Addressed by the SEI CERT Perl Coding Standard) > 1179 (SEI CERT Perl Coding Standard - Guidelines 01. Input Validation and Data Sanitization (IDS)) > 22 (Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal'))

The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.Directory traversalPath traversal

1178 (Weaknesses Addressed by the SEI CERT Perl Coding Standard) > 1179 (SEI CERT Perl Coding Standard - Guidelines 01. Input Validation and Data Sanitization (IDS)) > 134 (Use of Externally-Controlled Format String)

The product uses a function that accepts a format string as an argument, but the format string originates from an external source.

Variant - a weakness that is linked to a certain type of product, typically involving a specific language or technology. More specific than a Base weakness. Variant level weaknesses typically describe issues in terms of 3 to 5 of the following dimensions: behavior, property, technology, language, and resource.Improper Validation of Array Index - (129)

1178 (Weaknesses Addressed by the SEI CERT Perl Coding Standard) > 1179 (SEI CERT Perl Coding Standard - Guidelines 01. Input Validation and Data Sanitization (IDS)) > 129 (Improper Validation of Array Index)

The product uses untrusted input when calculating or using an array index, but the product does not validate or incorrectly validates the index to ensure the index references a valid position within the array.out-of-bounds array indexindex-out-of-rangearray index underflow

1178 (Weaknesses Addressed by the SEI CERT Perl Coding Standard) > 1179 (SEI CERT Perl Coding Standard - Guidelines 01. Input Validation and Data Sanitization (IDS)) > 789 (Memory Allocation with Excessive Size Value)

The product allocates memory based on an untrusted, large size value, but it does not ensure that the size is within expected limits, allowing arbitrary amounts of memory to be allocated.Stack Exhaustion

Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource.Improper Encoding or Escaping of Output - (116)

1178 (Weaknesses Addressed by the SEI CERT Perl Coding Standard) > 1179 (SEI CERT Perl Coding Standard - Guidelines 01. Input Validation and Data Sanitization (IDS)) > 116 (Improper Encoding or Escaping of Output)

The product prepares a structured message for communication with another component, but encoding or escaping of the data is either missing or done incorrectly. As a result, the intended structure of the message is not preserved.Output SanitizationOutput ValidationOutput Encoding

1178 (Weaknesses Addressed by the SEI CERT Perl Coding Standard) > 1179 (SEI CERT Perl Coding Standard - Guidelines 01. Input Validation and Data Sanitization (IDS)) > 77 (Improper Neutralization of Special Elements used in a Command ('Command Injection'))

The product constructs all or part of a command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended command when it is sent to a downstream component.

1178 (Weaknesses Addressed by the SEI CERT Perl Coding Standard) > 1179 (SEI CERT Perl Coding Standard - Guidelines 01. Input Validation and Data Sanitization (IDS)) > 95 (Improper Neutralization of Directives in Dynamically Evaluated Code ('Eval Injection'))

The product receives input from an upstream component, but it does not neutralize or incorrectly neutralizes code syntax before using the input in a dynamic evaluation call (e.g. "eval").

Category - a CWE entry that contains a set of other entries that share a common characteristic.SEI CERT Perl Coding Standard - Guidelines 02. Declarations and Initialization (DCL) - (1180)

1178 (Weaknesses Addressed by the SEI CERT Perl Coding Standard) > 1180 (SEI CERT Perl Coding Standard - Guidelines 02. Declarations and Initialization (DCL))

Weaknesses in this category are related to the rules and recommendations in the Declarations and Initialization (DCL) section of the SEI CERT Perl Coding Standard.

Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.Function Call with Incorrectly Specified Arguments - (628)

1178 (Weaknesses Addressed by the SEI CERT Perl Coding Standard) > 1180 (SEI CERT Perl Coding Standard - Guidelines 02. Declarations and Initialization (DCL)) > 628 (Function Call with Incorrectly Specified Arguments)

The product calls a function, procedure, or routine with arguments that are not correctly specified, leading to always-incorrect behavior and resultant weaknesses.

1178 (Weaknesses Addressed by the SEI CERT Perl Coding Standard) > 1180 (SEI CERT Perl Coding Standard - Guidelines 02. Declarations and Initialization (DCL)) > 456 (Missing Initialization of a Variable)

The product does not initialize critical variables, which causes the execution environment to use unexpected values.

1178 (Weaknesses Addressed by the SEI CERT Perl Coding Standard) > 1180 (SEI CERT Perl Coding Standard - Guidelines 02. Declarations and Initialization (DCL)) > 457 (Use of Uninitialized Variable)

The code uses a variable that has not been initialized, leading to unpredictable or unintended results.

1178 (Weaknesses Addressed by the SEI CERT Perl Coding Standard) > 1180 (SEI CERT Perl Coding Standard - Guidelines 02. Declarations and Initialization (DCL)) > 477 (Use of Obsolete Function)

The code uses deprecated or obsolete functions, which suggests that the code has not been actively reviewed or maintained.

Category - a CWE entry that contains a set of other entries that share a common characteristic.SEI CERT Perl Coding Standard - Guidelines 03. Expressions (EXP) - (1181)

1178 (Weaknesses Addressed by the SEI CERT Perl Coding Standard) > 1181 (SEI CERT Perl Coding Standard - Guidelines 03. Expressions (EXP))

Weaknesses in this category are related to the rules and recommendations in the Expressions (EXP) section of the SEI CERT Perl Coding Standard.

1178 (Weaknesses Addressed by the SEI CERT Perl Coding Standard) > 1181 (SEI CERT Perl Coding Standard - Guidelines 03. Expressions (EXP)) > 394 (Unexpected Status Code or Return Value)

The product does not properly check when a function or operation returns a value that is legitimate for the function, but is not expected by the product.

1178 (Weaknesses Addressed by the SEI CERT Perl Coding Standard) > 1181 (SEI CERT Perl Coding Standard - Guidelines 03. Expressions (EXP)) > 783 (Operator Precedence Logic Error)

The product uses an expression in which operator precedence causes incorrect logic to be used.

1178 (Weaknesses Addressed by the SEI CERT Perl Coding Standard) > 1181 (SEI CERT Perl Coding Standard - Guidelines 03. Expressions (EXP)) > 477 (Use of Obsolete Function)

The code uses deprecated or obsolete functions, which suggests that the code has not been actively reviewed or maintained.

1178 (Weaknesses Addressed by the SEI CERT Perl Coding Standard) > 1181 (SEI CERT Perl Coding Standard - Guidelines 03. Expressions (EXP)) > 248 (Uncaught Exception)

An exception is thrown from a function, but it is not caught.

1178 (Weaknesses Addressed by the SEI CERT Perl Coding Standard) > 1181 (SEI CERT Perl Coding Standard - Guidelines 03. Expressions (EXP)) > 391 (Unchecked Error Condition)

[PLANNED FOR DEPRECATION. SEE MAINTENANCE NOTES AND CONSIDER CWE-252, CWE-248, OR CWE-1069.] Ignoring exceptions and other error conditions may allow an attacker to induce unexpected behavior unnoticed.

1178 (Weaknesses Addressed by the SEI CERT Perl Coding Standard) > 1181 (SEI CERT Perl Coding Standard - Guidelines 03. Expressions (EXP)) > 460 (Improper Cleanup on Thrown Exception)

The product does not clean up its state or incorrectly cleans up its state when an exception is thrown, leading to unexpected state or control flow.

1178 (Weaknesses Addressed by the SEI CERT Perl Coding Standard) > 1181 (SEI CERT Perl Coding Standard - Guidelines 03. Expressions (EXP)) > 705 (Incorrect Control Flow Scoping)

The product does not properly return control flow to the proper location after it has completed a task or detected an unusual condition.

1178 (Weaknesses Addressed by the SEI CERT Perl Coding Standard) > 1181 (SEI CERT Perl Coding Standard - Guidelines 03. Expressions (EXP)) > 754 (Improper Check for Unusual or Exceptional Conditions)

The product does not check or incorrectly checks for unusual or exceptional conditions that are not expected to occur frequently during day to day operation of the product.

1178 (Weaknesses Addressed by the SEI CERT Perl Coding Standard) > 1181 (SEI CERT Perl Coding Standard - Guidelines 03. Expressions (EXP)) > 252 (Unchecked Return Value)

The product does not check the return value from a method or function, which can prevent it from detecting unexpected states and conditions.

Chain - a Compound Element that is a sequence of two or more separate weaknesses that can be closely linked together within software. One weakness, X, can directly create the conditions that are necessary to cause another weakness, Y, to enter a vulnerable condition. When this happens, CWE refers to X as "primary" to Y, and Y is "resultant" from X. Chains can involve more than two weaknesses, and in some cases, they might have a tree-like structure.Unchecked Return Value to NULL Pointer Dereference - (690)

1178 (Weaknesses Addressed by the SEI CERT Perl Coding Standard) > 1181 (SEI CERT Perl Coding Standard - Guidelines 03. Expressions (EXP)) > 690 (Unchecked Return Value to NULL Pointer Dereference)

The product does not check for an error after calling a function that can return with a NULL pointer if the function fails, which leads to a resultant NULL pointer dereference.

Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.Function Call with Incorrectly Specified Arguments - (628)

1178 (Weaknesses Addressed by the SEI CERT Perl Coding Standard) > 1181 (SEI CERT Perl Coding Standard - Guidelines 03. Expressions (EXP)) > 628 (Function Call with Incorrectly Specified Arguments)

The product calls a function, procedure, or routine with arguments that are not correctly specified, leading to always-incorrect behavior and resultant weaknesses.

Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.Returning a Mutable Object to an Untrusted Caller - (375)

1178 (Weaknesses Addressed by the SEI CERT Perl Coding Standard) > 1181 (SEI CERT Perl Coding Standard - Guidelines 03. Expressions (EXP)) > 375 (Returning a Mutable Object to an Untrusted Caller)

Sending non-cloned mutable data as a return value may result in that data being altered or deleted by the calling function.

1178 (Weaknesses Addressed by the SEI CERT Perl Coding Standard) > 1181 (SEI CERT Perl Coding Standard - Guidelines 03. Expressions (EXP)) > 597 (Use of Wrong Operator in String Comparison)

The product uses the wrong operator when comparing a string, such as using "==" when the .equals() method should be used instead.

Category - a CWE entry that contains a set of other entries that share a common characteristic.SEI CERT Perl Coding Standard - Guidelines 04. Integers (INT) - (1182)

1178 (Weaknesses Addressed by the SEI CERT Perl Coding Standard) > 1182 (SEI CERT Perl Coding Standard - Guidelines 04. Integers (INT))

Weaknesses in this category are related to the rules and recommendations in the Integers (INT) section of the SEI CERT Perl Coding Standard.

Category - a CWE entry that contains a set of other entries that share a common characteristic.Numeric Errors - (189)

1178 (Weaknesses Addressed by the SEI CERT Perl Coding Standard) > 1182 (SEI CERT Perl Coding Standard - Guidelines 04. Integers (INT)) > 189 (Numeric Errors)

Weaknesses in this category are related to improper calculation or conversion of numbers.

Category - a CWE entry that contains a set of other entries that share a common characteristic.SEI CERT Perl Coding Standard - Guidelines 05. Strings (STR) - (1183)

1178 (Weaknesses Addressed by the SEI CERT Perl Coding Standard) > 1183 (SEI CERT Perl Coding Standard - Guidelines 05. Strings (STR))

Weaknesses in this category are related to the rules and recommendations in the Strings (STR) section of the SEI CERT Perl Coding Standard.

Category - a CWE entry that contains a set of other entries that share a common characteristic.SEI CERT Perl Coding Standard - Guidelines 06. Object-Oriented Programming (OOP) - (1184)

1178 (Weaknesses Addressed by the SEI CERT Perl Coding Standard) > 1184 (SEI CERT Perl Coding Standard - Guidelines 06. Object-Oriented Programming (OOP))

Weaknesses in this category are related to the rules and recommendations in the Object-Oriented Programming (OOP) section of the SEI CERT Perl Coding Standard.

Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.Access to Critical Private Variable via Public Method - (767)

1178 (Weaknesses Addressed by the SEI CERT Perl Coding Standard) > 1184 (SEI CERT Perl Coding Standard - Guidelines 06. Object-Oriented Programming (OOP)) > 767 (Access to Critical Private Variable via Public Method)

The product defines a public method that reads or modifies a private variable.

Category - a CWE entry that contains a set of other entries that share a common characteristic.SEI CERT Perl Coding Standard - Guidelines 07. File Input and Output (FIO) - (1185)

1178 (Weaknesses Addressed by the SEI CERT Perl Coding Standard) > 1185 (SEI CERT Perl Coding Standard - Guidelines 07. File Input and Output (FIO))

Weaknesses in this category are related to the rules and recommendations in the File Input and Output (FIO) section of the SEI CERT Perl Coding Standard.

Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.Improper Link Resolution Before File Access ('Link Following') - (59)

1178 (Weaknesses Addressed by the SEI CERT Perl Coding Standard) > 1185 (SEI CERT Perl Coding Standard - Guidelines 07. File Input and Output (FIO)) > 59 (Improper Link Resolution Before File Access ('Link Following'))

The product attempts to access a file based on the filename, but it does not properly prevent that filename from identifying a link or shortcut that resolves to an unintended resource.insecure temporary fileZip Slip

Category - a CWE entry that contains a set of other entries that share a common characteristic.SEI CERT Perl Coding Standard - Guidelines 50. Miscellaneous (MSC) - (1186)

1178 (Weaknesses Addressed by the SEI CERT Perl Coding Standard) > 1186 (SEI CERT Perl Coding Standard - Guidelines 50. Miscellaneous (MSC))

Weaknesses in this category are related to the rules and recommendations in the Miscellaneous (MSC) section of the SEI CERT Perl Coding Standard.

1178 (Weaknesses Addressed by the SEI CERT Perl Coding Standard) > 1186 (SEI CERT Perl Coding Standard - Guidelines 50. Miscellaneous (MSC)) > 561 (Dead Code)

The product contains dead code, which can never be executed.

1178 (Weaknesses Addressed by the SEI CERT Perl Coding Standard) > 1186 (SEI CERT Perl Coding Standard - Guidelines 50. Miscellaneous (MSC)) > 563 (Assignment to Variable without Use)

The variable's value is assigned but never used, making it a dead store.Unused Variable

Vulnerability Mapping Notes

Usage: PROHIBITED

(this CWE ID must not be used to map to real-world vulnerabilities)

Reason: View

Rationale:

This entry is a View. Views are not weaknesses and therefore inappropriate to describe the root causes of vulnerabilities.

Comments:

Use this View or other Views to search and navigate for the appropriate weakness.

Notes

Relationship

The relationships in this view were determined based on specific statements within the rules from the standard. Not all rules have direct relationships to individual weaknesses, although they likely have chaining relationships in specific circumstances.

References

[REF-1011] The Software Engineering Institute. "SEI CERT Perl Coding Standard". <https://wiki.sei.cmu.edu/confluence/display/perl/SEI+CERT+Perl+Coding+Standard>.

View Metrics

	CWEs in this view		Total CWEs
Weaknesses	26	out of	938
Categories	9	out of	374
Views	0	out of	50
Total	35	out of	1362

Content History

Submissions
Submission Date	Submitter	Organization
2019-01-08 (CWE 3.3, 2019-06-20)	CWE Content Team	MITRE
2019-01-08 (CWE 3.3, 2019-06-20)
Modifications
Modification Date	Modifier	Organization
2020-02-24	CWE Content Team	MITRE
2020-02-24	updated View_Audience
2023-06-29	CWE Content Team	MITRE
2023-06-29	updated Mapping_Notes

View Components

Weakness ID: 767

Vulnerability Mapping: ALLOWEDThis CWE ID may be used to map to real-world vulnerabilities
Abstraction: BaseBase - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.

View customized information:

For users who are interested in more notional aspects of a weakness. Example: educators, technical writers, and project/program managers. For users who are concerned with the practical application and details about the nature of a weakness and how to prevent it from happening. Example: tool developers, security researchers, pen-testers, incident response analysts. For users who are mapping an issue to CWE/CAPEC IDs, i.e., finding the most appropriate CWE for a specific issue (e.g., a CVE record). Example: tool developers, security researchers. For users who wish to see all available information for the CWE/CAPEC entry. For users who want to customize what details are displayed.

Description

The product defines a public method that reads or modifies a private variable.

Extended Description

If an attacker modifies the variable to contain unexpected values, this could violate assumptions from other parts of the code. Additionally, if an attacker can read the private variable, it may expose sensitive information or make it easier to launch further attacks.

Relationships

This table shows the weaknesses and high level categories that are related to this weakness. These relationships are defined as ChildOf, ParentOf, MemberOf and give insight to similar items that may exist at higher and lower levels of abstraction. In addition, relationships such as PeerOf and CanAlsoBe are defined to show similar weaknesses that the user may want to explore.

Relevant to the view "Research Concepts" (CWE-1000)

Nature	Type	ID	Name
ChildOf	Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource.	668	Exposure of Resource to Wrong Sphere

Relevant to the view "Software Development" (CWE-699)

Nature	Type	ID	Name
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	275	Permission Issues

Modes Of Introduction

The different Modes of Introduction provide information about how and when this weakness may be introduced. The Phase identifies a point in the life cycle at which introduction may occur, while the Note provides a typical scenario related to introduction during the given phase.

Phase	Note
Implementation

Applicable Platforms

This listing shows possible areas for which the given weakness could appear. These may be for specific named Languages, Operating Systems, Architectures, Paradigms, Technologies, or a class of such platforms. The platform is listed along with how frequently the given weakness appears for that instance.

Languages

C++ (Undetermined Prevalence)

C# (Undetermined Prevalence)

Java (Undetermined Prevalence)

Common Consequences

This table specifies different individual consequences associated with the weakness. The Scope identifies the application security area that is violated, while the Impact describes the negative technical impact that arises if an adversary succeeds in exploiting this weakness. The Likelihood provides information about how likely the specific consequence is expected to be seen relative to the other consequences in the list. For example, there may be high likelihood that a weakness will be exploited to achieve a certain impact, but a low likelihood that it will be exploited to achieve a different impact.

Scope	Impact	Likelihood
Integrity Other	Technical Impact: Modify Application Data; Other

Demonstrative Examples

Example 1

The following example declares a critical variable to be private, and then allows the variable to be modified by public methods.

(bad code)

Example Language: C++

private: float price;
public: void changePrice(float newPrice) {

price = newPrice;

}

Example 2

The following example could be used to implement a user forum where a single user (UID) can switch between multiple profiles (PID).

(bad code)

Example Language: Java

public class Client {

private int UID;
public int PID;
private String userName;
public Client(String userName){

PID = getDefaultProfileID();
UID = mapUserNametoUID( userName );
this.userName = userName;

}
public void setPID(int ID) {

UID = ID;

}

The programmer implemented setPID with the intention of modifying the PID variable, but due to a typo. accidentally specified the critical variable UID instead. If the program allows profile IDs to be between 1 and 10, but a UID of 1 means the user is treated as an admin, then a user could gain administrative privileges as a result of this typo.

Potential Mitigations

Phase: Implementation

Use class accessor and mutator methods appropriately. Perform validation when accepting data from a public method that is intended to modify a critical private variable. Also be sure that appropriate access controls are being applied when a public method interfaces with critical data.

Memberships

This MemberOf Relationships table shows additional CWE Categories and Views that reference this weakness as a member. This information is often useful in understanding where a weakness fits within the context of external information sources.

Nature	Type	ID	Name
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	963	SFP Secondary Cluster: Exposed Data
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1184	SEI CERT Perl Coding Standard - Guidelines 06. Object-Oriented Programming (OOP)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1403	Comprehensive Categorization: Exposed Resource

Vulnerability Mapping Notes

Usage: ALLOWED

(this CWE ID could be used to map to real-world vulnerabilities)

Reason: Acceptable-Use

Rationale:

This CWE entry is at the Base level of abstraction, which is a preferred level of abstraction for mapping to the root causes of vulnerabilities.

Comments:

Carefully read both the name and description to ensure that this mapping is an appropriate fit. Do not try to 'force' a mapping to a lower-level Base/Variant simply to comply with this preferred level of abstraction.

Notes

Maintenance

This entry is closely associated with access control for public methods. If the public methods are restricted with proper access controls, then the information in the private variable will not be exposed to unexpected parties. There may be chaining or composite relationships between improper access controls and this weakness.

Taxonomy Mappings

Mapped Taxonomy Name	Node ID	Fit	Mapped Node Name
CLASP			Failure to protect stored data from modification
Software Fault Patterns	SFP23		Exposed Data
SEI CERT Perl Coding Standard	OOP31-PL	Imprecise	Do not access private variables or subroutines in other packages

Content History

Submissions
Submission Date	Submitter	Organization
2009-03-03 (CWE 1.4, 2009-05-27)	CWE Content Team	MITRE
2009-03-03 (CWE 1.4, 2009-05-27)
Modifications
Modification Date	Modifier	Organization
2011-06-01	CWE Content Team	MITRE
2011-06-01	updated Common_Consequences
2012-05-11	CWE Content Team	MITRE
2012-05-11	updated Relationships
2014-07-30	CWE Content Team	MITRE
2014-07-30	updated Relationships, Taxonomy_Mappings
2017-11-08	CWE Content Team	MITRE
2017-11-08	updated Likelihood_of_Exploit, Relationships, Taxonomy_Mappings
2019-01-03	CWE Content Team	MITRE
2019-01-03	updated Taxonomy_Mappings
2020-02-24	CWE Content Team	MITRE
2020-02-24	updated Relationships
2021-03-15	CWE Content Team	MITRE
2021-03-15	updated Relationships
2023-01-31	CWE Content Team	MITRE
2023-01-31	updated Description
2023-04-27	CWE Content Team	MITRE
2023-04-27	updated Relationships, Time_of_Introduction, Type
2023-06-29	CWE Content Team	MITRE
2023-06-29	updated Mapping_Notes

Weakness ID: 563

View customized information:

Description

The variable's value is assigned but never used, making it a dead store.

Extended Description

After the assignment, the variable is either assigned another value or goes out of scope. It is likely that the variable is simply vestigial, but it is also possible that the unused variable points out a bug.

Alternate Terms

Unused Variable

Relationships

Relevant to the view "Research Concepts" (CWE-1000)

Nature	Type	ID	Name
ChildOf	Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource.	1164	Irrelevant Code

Relevant to the view "Software Development" (CWE-699)

Nature	Type	ID	Name
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1006	Bad Coding Practices

Modes Of Introduction

Phase	Note
Implementation

Common Consequences

Scope	Impact	Likelihood
Other	Technical Impact: Quality Degradation; Varies by Context This weakness could be an indication of a bug in the program or a deprecated variable that was not removed and is an indication of poor quality. This could lead to further bugs and the introduction of weaknesses.

Demonstrative Examples

Example 1

The following code excerpt assigns to the variable r and then overwrites the value without using it.

(bad code)

Example Language: C

r = getName();
r = getNewBuffer(buf);

Potential Mitigations

Phase: Implementation

Remove unused variables from the code.

Weakness Ordinalities

Ordinality	Description
Indirect	(where the weakness is a quality issue that might indirectly make it easier to introduce security-relevant weaknesses or make them more difficult to detect)

Detection Methods

Automated Static Analysis

Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.)

Effectiveness: High

Memberships

Nature	Type	ID	Name
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	747	CERT C Secure Coding Standard (2008) Chapter 14 - Miscellaneous (MSC)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	883	CERT C++ Secure Coding Section 49 - Miscellaneous (MSC)
MemberOf	View - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries).	884	CWE Cross-section
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	886	SFP Primary Cluster: Unused entities
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1186	SEI CERT Perl Coding Standard - Guidelines 50. Miscellaneous (MSC)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1412	Comprehensive Categorization: Poor Coding Practices

Vulnerability Mapping Notes

Usage: ALLOWED

(this CWE ID could be used to map to real-world vulnerabilities)

Reason: Acceptable-Use

Rationale:

This CWE entry is at the Base level of abstraction, which is a preferred level of abstraction for mapping to the root causes of vulnerabilities.

Comments:

Taxonomy Mappings

Mapped Taxonomy Name	Node ID	Fit	Mapped Node Name
CERT C Secure Coding	MSC00-C		Compile cleanly at high warning levels
SEI CERT Perl Coding Standard	MSC01-PL	Imprecise	Detect and remove unused variables
Software Fault Patterns	SFP2		Unused Entities

Content History

Submissions
Submission Date	Submitter	Organization
2006-07-19 (CWE Draft 3, 2006-07-19)	Anonymous Tool Vendor (under NDA)
2006-07-19 (CWE Draft 3, 2006-07-19)
Modifications
Modification Date	Modifier	Organization
2008-07-01	Eric Dalci	Cigital
2008-07-01	updated Potential_Mitigations, Time_of_Introduction
2008-09-08	CWE Content Team	MITRE
2008-09-08	updated Description, Relationships, Other_Notes, Taxonomy_Mappings
2008-11-24	CWE Content Team	MITRE
2008-11-24	updated Relationships, Taxonomy_Mappings
2009-05-27	CWE Content Team	MITRE
2009-05-27	updated Demonstrative_Examples
2011-06-01	CWE Content Team	MITRE
2011-06-01	updated Common_Consequences
2011-06-27	CWE Content Team	MITRE
2011-06-27	updated Common_Consequences
2011-09-13	CWE Content Team	MITRE
2011-09-13	updated Relationships, Taxonomy_Mappings
2012-05-11	CWE Content Team	MITRE
2012-05-11	updated Common_Consequences, Relationships
2012-10-30	CWE Content Team	MITRE
2012-10-30	updated Potential_Mitigations
2014-06-23	CWE Content Team	MITRE
2014-06-23	updated Common_Consequences, Description, Name, Other_Notes
2014-07-30	CWE Content Team	MITRE
2014-07-30	updated Taxonomy_Mappings
2017-11-08	CWE Content Team	MITRE
2017-11-08	updated Alternate_Terms, Name, Relationships, Taxonomy_Mappings
2019-01-03	CWE Content Team	MITRE
2019-01-03	updated Relationships, Taxonomy_Mappings, Weakness_Ordinalities
2020-02-24	CWE Content Team	MITRE
2020-02-24	updated Relationships
2021-03-15	CWE Content Team	MITRE
2021-03-15	updated Relationships
2023-04-27	CWE Content Team	MITRE
2023-04-27	updated Detection_Factors, Relationships, Type
2023-06-29	CWE Content Team	MITRE
2023-06-29	updated Mapping_Notes
2024-02-29 (CWE 4.14, 2024-02-29)	CWE Content Team	MITRE
2024-02-29 (CWE 4.14, 2024-02-29)	updated Demonstrative_Examples
Previous Entry Names
Change Date	Previous Entry Name
2014-06-23	Unused Variable

2017-11-08	Assignment to Variable without Use ('Unused Variable')

Weakness ID: 561

View customized information:

Description

The product contains dead code, which can never be executed.

Extended Description

Dead code is code that can never be executed in a running program. The surrounding code makes it impossible for a section of code to ever be executed.

Relationships

Relevant to the view "Research Concepts" (CWE-1000)

Nature	Type	ID	Name
ChildOf	Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource.	1164	Irrelevant Code
CanFollow	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	570	Expression is Always False
CanFollow	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	571	Expression is Always True

Relevant to the view "Software Development" (CWE-699)

Nature	Type	ID	Name
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1006	Bad Coding Practices

Modes Of Introduction

Phase	Note
Implementation

Applicable Platforms

Languages

Class: Not Language-Specific (Undetermined Prevalence)

Common Consequences

Scope	Impact	Likelihood
Other	Technical Impact: Quality Degradation Dead code that results from code that can never be executed is an indication of problems with the source code that needs to be fixed and is an indication of poor quality.
Other	Technical Impact: Reduce Maintainability

Demonstrative Examples

Example 1

The condition for the second if statement is impossible to satisfy. It requires that the variables be non-null. However, on the only path where s can be assigned a non-null value, there is a return statement.

(bad code)

Example Language: C++

String s = null;
if (b) {

s = "Yes";
return;

}

if (s != null) {

Dead();

}

Example 2

In the following class, two private methods call each other, but since neither one is ever invoked from anywhere else, they are both dead code.

(bad code)

Example Language: Java

public class DoubleDead {

private void doTweedledee() {

doTweedledumb();

}
private void doTweedledumb() {

doTweedledee();

}
public static void main(String[] args) {

System.out.println("running DoubleDead");

}

(In this case it is a good thing that the methods are dead: invoking either one would cause an infinite loop.)

Example 3

The field named glue is not used in the following class. The author of the class has accidentally put quotes around the field name, transforming it into a string constant.

(bad code)

Example Language: Java

public class Dead {

String glue;

public String getGlue() {

return "glue";

}

Observed Examples

Reference	Description
CVE-2014-1266	chain: incorrect "goto" in Apple SSL product bypasses certificate validation, allowing Adversary-in-the-Middle (AITM) attack (Apple "goto fail" bug). CWE-705 (Incorrect Control Flow Scoping) -> CWE-561 (Dead Code) -> CWE-295 (Improper Certificate Validation) -> CWE-393 (Return of Wrong Status Code) -> CWE-300 (Channel Accessible by Non-Endpoint).

Potential Mitigations

Phase: Implementation

Remove dead code before deploying the application.

Phase: Testing

Use a static analysis tool to spot dead code.

Weakness Ordinalities

Ordinality	Description
Indirect	(where the weakness is a quality issue that might indirectly make it easier to introduce security-relevant weaknesses or make them more difficult to detect)

Detection Methods

Architecture or Design Review

According to SOAR, the following detection techniques may be useful:

Highly cost effective:

Inspection (IEEE 1028 standard) (can apply to requirements, design, source code, etc.)

Formal Methods / Correct-By-Construction

Cost effective for partial coverage:

Attack Modeling

Effectiveness: High

Automated Static Analysis - Binary or Bytecode

According to SOAR, the following detection techniques may be useful:

Highly cost effective:

Binary / Bytecode Quality Analysis

Compare binary / bytecode to application permission manifest

Effectiveness: High

Dynamic Analysis with Manual Results Interpretation

According to SOAR, the following detection techniques may be useful:

Cost effective for partial coverage:

Automated Monitored Execution

Effectiveness: SOAR Partial

Automated Static Analysis

According to SOAR, the following detection techniques may be useful:

Cost effective for partial coverage:

Permission Manifest Analysis

Effectiveness: SOAR Partial

Automated Static Analysis - Source Code

According to SOAR, the following detection techniques may be useful:

Highly cost effective:

Source Code Quality Analyzer

Cost effective for partial coverage:

Warning Flags

Source code Weakness Analyzer

Context-configured Source Code Weakness Analyzer

Effectiveness: High

Dynamic Analysis with Automated Results Interpretation

According to SOAR, the following detection techniques may be useful:

Cost effective for partial coverage:

Web Application Scanner

Web Services Scanner

Database Scanners

Effectiveness: SOAR Partial

Manual Static Analysis - Source Code

According to SOAR, the following detection techniques may be useful:

Highly cost effective:

Manual Source Code Review (not inspections)

Cost effective for partial coverage:

Focused Manual Spotcheck - Focused manual analysis of source

Effectiveness: High

Memberships

Nature	Type	ID	Name
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	747	CERT C Secure Coding Standard (2008) Chapter 14 - Miscellaneous (MSC)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	883	CERT C++ Secure Coding Section 49 - Miscellaneous (MSC)
MemberOf	View - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries).	884	CWE Cross-section
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	886	SFP Primary Cluster: Unused entities
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1130	CISQ Quality Measures (2016) - Maintainability
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1186	SEI CERT Perl Coding Standard - Guidelines 50. Miscellaneous (MSC)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1307	CISQ Quality Measures - Maintainability
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1412	Comprehensive Categorization: Poor Coding Practices

Vulnerability Mapping Notes

Usage: ALLOWED

(this CWE ID could be used to map to real-world vulnerabilities)

Reason: Acceptable-Use

Rationale:

This CWE entry is at the Base level of abstraction, which is a preferred level of abstraction for mapping to the root causes of vulnerabilities.

Comments:

Taxonomy Mappings

Mapped Taxonomy Name	Node ID	Fit	Mapped Node Name
CERT C Secure Coding	MSC07-C		Detect and remove dead code
SEI CERT Perl Coding Standard	MSC00-PL	Exact	Detect and remove dead code
Software Fault Patterns	SFP2		Unused Entities
OMG ASCMM	ASCMM-MNT-20

References

[REF-960] Object Management Group (OMG). "Automated Source Code Maintainability Measure (ASCMM)". ASCMM-MNT-20. 2016-01. <https://www.omg.org/spec/ASCMM/>. URL validated: 2023-04-07.

Content History

Submissions
Submission Date	Submitter	Organization
2006-07-19 (CWE Draft 3, 2006-07-19)	Anonymous Tool Vendor (under NDA)
2006-07-19 (CWE Draft 3, 2006-07-19)
Modifications
Modification Date	Modifier	Organization
2008-07-01	Eric Dalci	Cigital
2008-07-01	updated Potential_Mitigations, Time_of_Introduction
2008-09-08	CWE Content Team	MITRE
2008-09-08	updated Description, Relationships, Other_Notes, Taxonomy_Mappings
2008-11-24	CWE Content Team	MITRE
2008-11-24	updated Relationships, Taxonomy_Mappings
2009-05-27	CWE Content Team	MITRE
2009-05-27	updated Demonstrative_Examples
2009-07-27	CWE Content Team	MITRE
2009-07-27	updated Demonstrative_Examples
2009-10-29	CWE Content Team	MITRE
2009-10-29	updated Common_Consequences, Other_Notes
2011-06-01	CWE Content Team	MITRE
2011-06-01	updated Common_Consequences
2011-09-13	CWE Content Team	MITRE
2011-09-13	updated Relationships, Taxonomy_Mappings
2012-05-11	CWE Content Team	MITRE
2012-05-11	updated Common_Consequences, Relationships
2012-10-30	CWE Content Team	MITRE
2012-10-30	updated Potential_Mitigations
2014-06-23	CWE Content Team	MITRE
2014-06-23	updated Observed_Examples
2014-07-30	CWE Content Team	MITRE
2014-07-30	updated Detection_Factors, Taxonomy_Mappings
2017-11-08	CWE Content Team	MITRE
2017-11-08	updated Relationships, Taxonomy_Mappings
2019-01-03	CWE Content Team	MITRE
2019-01-03	updated Common_Consequences, References, Relationships, Taxonomy_Mappings, Weakness_Ordinalities
2019-06-20	CWE Content Team	MITRE
2019-06-20	updated Type
2020-02-24	CWE Content Team	MITRE
2020-02-24	updated Applicable_Platforms, Observed_Examples, Relationships
2020-08-20	CWE Content Team	MITRE
2020-08-20	updated Relationships
2021-03-15	CWE Content Team	MITRE
2021-03-15	updated Relationships
2021-07-20	CWE Content Team	MITRE
2021-07-20	updated Observed_Examples
2023-01-31	CWE Content Team	MITRE
2023-01-31	updated Description
2023-04-27	CWE Content Team	MITRE
2023-04-27	updated References, Relationships
2023-06-29	CWE Content Team	MITRE
2023-06-29	updated Mapping_Notes
2024-02-29 (CWE 4.14, 2024-02-29)	CWE Content Team	MITRE
2024-02-29 (CWE 4.14, 2024-02-29)	updated Demonstrative_Examples

Weakness ID: 628

View customized information:

Description

The product calls a function, procedure, or routine with arguments that are not correctly specified, leading to always-incorrect behavior and resultant weaknesses.

Extended Description

There are multiple ways in which this weakness can be introduced, including:

the wrong variable or reference;
an incorrect number of arguments;
incorrect order of arguments;
wrong type of arguments; or
wrong value.

Relationships

Relevant to the view "Research Concepts" (CWE-1000)

Nature	Type	ID	Name
ChildOf	Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource.	573	Improper Following of Specification by Caller
ParentOf	Variant - a weakness that is linked to a certain type of product, typically involving a specific language or technology. More specific than a Base weakness. Variant level weaknesses typically describe issues in terms of 3 to 5 of the following dimensions: behavior, property, technology, language, and resource.	683	Function Call With Incorrect Order of Arguments
ParentOf	Variant - a weakness that is linked to a certain type of product, typically involving a specific language or technology. More specific than a Base weakness. Variant level weaknesses typically describe issues in terms of 3 to 5 of the following dimensions: behavior, property, technology, language, and resource.	685	Function Call With Incorrect Number of Arguments
ParentOf	Variant - a weakness that is linked to a certain type of product, typically involving a specific language or technology. More specific than a Base weakness. Variant level weaknesses typically describe issues in terms of 3 to 5 of the following dimensions: behavior, property, technology, language, and resource.	686	Function Call With Incorrect Argument Type
ParentOf	Variant - a weakness that is linked to a certain type of product, typically involving a specific language or technology. More specific than a Base weakness. Variant level weaknesses typically describe issues in terms of 3 to 5 of the following dimensions: behavior, property, technology, language, and resource.	687	Function Call With Incorrectly Specified Argument Value
ParentOf	Variant - a weakness that is linked to a certain type of product, typically involving a specific language or technology. More specific than a Base weakness. Variant level weaknesses typically describe issues in terms of 3 to 5 of the following dimensions: behavior, property, technology, language, and resource.	688	Function Call With Incorrect Variable or Reference as Argument

Relevant to the view "Software Development" (CWE-699)

Nature	Type	ID	Name
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1006	Bad Coding Practices

Modes Of Introduction

Phase	Note
Implementation

Applicable Platforms

Languages

Class: Not Language-Specific (Undetermined Prevalence)

Common Consequences

Scope	Impact	Likelihood
Other Access Control	Technical Impact: Quality Degradation; Gain Privileges or Assume Identity This weakness can cause unintended behavior and can lead to additional weaknesses such as allowing an attacker to gain unintended access to system resources.

Demonstrative Examples

Example 1

The following PHP method authenticates a user given a username/password combination but is called with the parameters in reverse order.

(bad code)

Example Language: PHP

function authenticate($username, $password) {

// authenticate user
...

}

authenticate($_POST['password'], $_POST['username']);

Example 2

This Perl code intends to record whether a user authenticated successfully or not, and to exit if the user fails to authenticate. However, when it calls ReportAuth(), the third argument is specified as 0 instead of 1, so it does not exit.

(bad code)

Example Language: Perl

sub ReportAuth {

my ($username, $result, $fatal) = @_;
PrintLog("auth: username=%s, result=%d", $username, $result);
if (($result ne "success") && $fatal) {

die "Failed!\n";

}

}

sub PrivilegedFunc
{

my $result = CheckAuth($username);
ReportAuth($username, $result, 0);
DoReallyImportantStuff();

}

Example 3

In the following Java snippet, the accessGranted() method is accidentally called with the static ADMIN_ROLES array rather than the user roles.

(bad code)

Example Language: Java

private static final String[] ADMIN_ROLES = ...;
public boolean void accessGranted(String resource, String user) {

String[] userRoles = getUserRoles(user);
return accessGranted(resource, ADMIN_ROLES);

}

private boolean void accessGranted(String resource, String[] userRoles) {

// grant or deny access based on user roles
...

}

Observed Examples

Reference	Description
CVE-2006-7049	The method calls the functions with the wrong argument order, which allows remote attackers to bypass intended access restrictions.

Potential Mitigations

Phase: Build and Compilation

Once found, these issues are easy to fix. Use code inspection tools and relevant compiler features to identify potential violations. Pay special attention to code that is not likely to be exercised heavily during QA.

Phase: Architecture and Design

Make sure your API's are stable before you use them in production code.

Weakness Ordinalities

Ordinality	Description
Primary	(where the weakness is a quality issue that might indirectly make it easier to introduce security-relevant weaknesses or make them more difficult to detect) This is usually primary to other weaknesses, but it can be resultant if the function's API or function prototype changes.

Detection Methods

Other

Since these bugs typically introduce incorrect behavior that is obvious to users, they are found quickly, unless they occur in rarely-tested code paths. Managing the correct number of arguments can be made more difficult in cases where format strings are used, or when variable numbers of arguments are supported.

Memberships

Nature	Type	ID	Name
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	736	CERT C Secure Coding Standard (2008) Chapter 3 - Declarations and Initialization (DCL)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	737	CERT C Secure Coding Standard (2008) Chapter 4 - Expressions (EXP)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	742	CERT C Secure Coding Standard (2008) Chapter 9 - Memory Management (MEM)
MemberOf	View - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries).	884	CWE Cross-section
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	998	SFP Secondary Cluster: Glitch in Computation
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1157	SEI CERT C Coding Standard - Guidelines 03. Expressions (EXP)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1180	SEI CERT Perl Coding Standard - Guidelines 02. Declarations and Initialization (DCL)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1181	SEI CERT Perl Coding Standard - Guidelines 03. Expressions (EXP)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1412	Comprehensive Categorization: Poor Coding Practices

Vulnerability Mapping Notes

Usage: ALLOWED

(this CWE ID could be used to map to real-world vulnerabilities)

Reason: Acceptable-Use

Rationale:

This CWE entry is at the Base level of abstraction, which is a preferred level of abstraction for mapping to the root causes of vulnerabilities.

Comments:

Taxonomy Mappings

Mapped Taxonomy Name	Node ID	Fit	Mapped Node Name
CERT C Secure Coding	DCL10-C		Maintain the contract between the writer and caller of variadic functions
CERT C Secure Coding	EXP37-C	CWE More Abstract	Call functions with the correct number and type of arguments
SEI CERT Perl Coding Standard	DCL00-PL	CWE More Abstract	Do not use subroutine prototypes
SEI CERT Perl Coding Standard	EXP33-PL	Imprecise	Do not invoke a function in a context for which it is not defined

Content History

Submissions
Submission Date	Submitter	Organization
2007-05-07 (CWE Draft 6, 2007-05-07)	CWE Content Team	MITRE
2007-05-07 (CWE Draft 6, 2007-05-07)
Modifications
Modification Date	Modifier	Organization
2008-09-08	CWE Content Team	MITRE
2008-09-08	updated Description, Relationships, Other_Notes, Weakness_Ordinalities
2008-11-24	CWE Content Team	MITRE
2008-11-24	updated Relationships, Taxonomy_Mappings
2009-10-29	CWE Content Team	MITRE
2009-10-29	updated Detection_Factors, Other_Notes, Weakness_Ordinalities
2010-02-16	CWE Content Team	MITRE
2010-02-16	updated Detection_Factors
2010-06-21	CWE Content Team	MITRE
2010-06-21	updated Description
2011-06-01	CWE Content Team	MITRE
2011-06-01	updated Common_Consequences
2011-06-27	CWE Content Team	MITRE
2011-06-27	updated Common_Consequences
2012-05-11	CWE Content Team	MITRE
2012-05-11	updated Common_Consequences, Demonstrative_Examples, Relationships
2012-10-30	CWE Content Team	MITRE
2012-10-30	updated Potential_Mitigations
2014-07-30	CWE Content Team	MITRE
2014-07-30	updated Relationships
2017-11-08	CWE Content Team	MITRE
2017-11-08	updated Applicable_Platforms, Taxonomy_Mappings
2019-01-03	CWE Content Team	MITRE
2019-01-03	updated Relationships, Taxonomy_Mappings
2020-02-24	CWE Content Team	MITRE
2020-02-24	updated Relationships
2021-03-15	CWE Content Team	MITRE
2021-03-15	updated Detection_Factors, Relationships
2023-04-27	CWE Content Team	MITRE
2023-04-27	updated Relationships
2023-06-29	CWE Content Team	MITRE
2023-06-29	updated Mapping_Notes
Previous Entry Names
Change Date	Previous Entry Name
2008-04-11	Incorrectly Specified Arguments

Weakness ID: 754

Vulnerability Mapping: ALLOWEDThis CWE ID could be used to map to real-world vulnerabilities in limited situations requiring careful review (with careful review of mapping notes)
Abstraction: ClassClass - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource.

View customized information:

Description

The product does not check or incorrectly checks for unusual or exceptional conditions that are not expected to occur frequently during day to day operation of the product.

Extended Description

The programmer may assume that certain events or conditions will never occur or do not need to be worried about, such as low memory conditions, lack of access to resources due to restrictive permissions, or misbehaving clients or components. However, attackers may intentionally trigger these unusual conditions, thus violating the programmer's assumptions, possibly introducing instability, incorrect behavior, or a vulnerability.

Note that this entry is not exclusively about the use of exceptions and exception handling, which are mechanisms for both checking and handling unusual or unexpected conditions.

Relationships

Relevant to the view "Research Concepts" (CWE-1000)

Nature	Type	ID	Name
ChildOf	Pillar - a weakness that is the most abstract type of weakness and represents a theme for all class/base/variant weaknesses related to it. A Pillar is different from a Category as a Pillar is still technically a type of weakness that describes a mistake, while a Category represents a common characteristic used to group related things.	703	Improper Check or Handling of Exceptional Conditions
ParentOf	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	252	Unchecked Return Value
ParentOf	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	253	Incorrect Check of Function Return Value
ParentOf	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	273	Improper Check for Dropped Privileges
ParentOf	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	354	Improper Validation of Integrity Check Value
ParentOf	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	391	Unchecked Error Condition
ParentOf	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	394	Unexpected Status Code or Return Value
ParentOf	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	476	NULL Pointer Dereference

Relevant to the view "Weaknesses for Simplified Mapping of Published Vulnerabilities" (CWE-1003)

Nature	Type	ID	Name
ParentOf	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	252	Unchecked Return Value
ParentOf	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	273	Improper Check for Dropped Privileges
ParentOf	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	476	NULL Pointer Dereference

Relevant to the view "Architectural Concepts" (CWE-1008)

Nature	Type	ID	Name
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1012	Cross Cutting

Background Details

Many functions will return some value about the success of their actions. This will alert the program whether or not to handle any errors caused by that function.

Modes Of Introduction

Phase	Note
Implementation	REALIZATION: This weakness is caused during implementation of an architectural security tactic.

Applicable Platforms

Languages

Class: Not Language-Specific (Undetermined Prevalence)

Common Consequences

Scope	Impact	Likelihood
Integrity Availability	Technical Impact: DoS: Crash, Exit, or Restart; Unexpected State The data which were produced as a result of a function call could be in a bad state upon return. If the return value is not checked, then this bad data may be used in operations, possibly leading to a crash or other unintended behaviors.

Likelihood Of Exploit

Medium

Demonstrative Examples

Example 1

Consider the following code segment:

(bad code)

Example Language: C

char buf[10], cp_buf[10];
fgets(buf, 10, stdin);
strcpy(cp_buf, buf);

The programmer expects that when fgets() returns, buf will contain a null-terminated string of length 9 or less. But if an I/O error occurs, fgets() will not null-terminate buf. Furthermore, if the end of the file is reached before any characters are read, fgets() returns without writing anything to buf. In both of these situations, fgets() signals that something unusual has happened by returning NULL, but in this code, the warning will not be noticed. The lack of a null terminator in buf can result in a buffer overflow in the subsequent call to strcpy().

Example 2

The following code does not check to see if memory allocation succeeded before attempting to use the pointer returned by malloc().

(bad code)

Example Language: C

buf = (char*) malloc(req_size);
strncpy(buf, xfer, req_size);

The traditional defense of this coding error is: "If my program runs out of memory, it will fail. It doesn't matter whether I handle the error or simply allow the program to die with a segmentation fault when it tries to dereference the null pointer." This argument ignores three important considerations:

Depending upon the type and size of the application, it may be possible to free memory that is being used elsewhere so that execution can continue.
It is impossible for the program to perform a graceful exit if required. If the program is performing an atomic operation, it can leave the system in an inconsistent state.
The programmer has lost the opportunity to record diagnostic information. Did the call to malloc() fail because req_size was too large or because there were too many requests being handled at the same time? Or was it caused by a memory leak that has built up over time? Without handling the error, there is no way to know.

Example 3

The following examples read a file into a byte array.

(bad code)

Example Language: C#

char[] byteArray = new char[1024];
for (IEnumerator i=users.GetEnumerator(); i.MoveNext() ;i.Current()) {

String userName = (String) i.Current();
String pFileName = PFILE_ROOT + "/" + userName;
StreamReader sr = new StreamReader(pFileName);
sr.Read(byteArray,0,1024);//the file is always 1k bytes
sr.Close();
processPFile(userName, byteArray);

}

(bad code)

Example Language: Java

FileInputStream fis;
byte[] byteArray = new byte[1024];
for (Iterator i=users.iterator(); i.hasNext();) {

String userName = (String) i.next();
String pFileName = PFILE_ROOT + "/" + userName;
FileInputStream fis = new FileInputStream(pFileName);
fis.read(byteArray); // the file is always 1k bytes
fis.close();
processPFile(userName, byteArray);

The code loops through a set of users, reading a private data file for each user. The programmer assumes that the files are always 1 kilobyte in size and therefore ignores the return value from Read(). If an attacker can create a smaller file, the program will recycle the remainder of the data from the previous user and treat it as though it belongs to the attacker.

Example 4

The following code does not check to see if the string returned by getParameter() is null before calling the member function compareTo(), potentially causing a NULL dereference.

(bad code)

Example Language: Java

String itemName = request.getParameter(ITEM_NAME);
if (itemName.compareTo(IMPORTANT_ITEM) == 0) {

...

}
...

The following code does not check to see if the string returned by the Item property is null before calling the member function Equals(), potentially causing a NULL dereference.

(bad code)

Example Language: Java

String itemName = request.Item(ITEM_NAME);
if (itemName.Equals(IMPORTANT_ITEM)) {

...

}
...

The traditional defense of this coding error is: "I know the requested value will always exist because.... If it does not exist, the program cannot perform the desired behavior so it doesn't matter whether I handle the error or simply allow the program to die dereferencing a null value." But attackers are skilled at finding unexpected paths through programs, particularly when exceptions are involved.

Example 5

The following code shows a system property that is set to null and later dereferenced by a programmer who mistakenly assumes it will always be defined.

(bad code)

Example Language: Java

System.clearProperty("os.name");
...
String os = System.getProperty("os.name");
if (os.equalsIgnoreCase("Windows 95")) System.out.println("Not supported");

Example 6

The following VB.NET code does not check to make sure that it has read 50 bytes from myfile.txt. This can cause DoDangerousOperation() to operate on an unexpected value.

(bad code)

Example Language: C#

Dim MyFile As New FileStream("myfile.txt", FileMode.Open, FileAccess.Read, FileShare.Read)
Dim MyArray(50) As Byte
MyFile.Read(MyArray, 0, 50)
DoDangerousOperation(MyArray(20))

In .NET, it is not uncommon for programmers to misunderstand Read() and related methods that are part of many System.IO classes. The stream and reader classes do not consider it to be unusual or exceptional if only a small amount of data becomes available. These classes simply add the small amount of data to the return buffer, and set the return value to the number of bytes or characters read. There is no guarantee that the amount of data returned is equal to the amount of data requested.

Example 7

This example takes an IP address from a user, verifies that it is well formed and then looks up the hostname and copies it into a buffer.

(bad code)

Example Language: C

void host_lookup(char *user_supplied_addr){

struct hostent *hp;
in_addr_t *addr;
char hostname[64];
in_addr_t inet_addr(const char *cp);

/*routine that ensures user_supplied_addr is in the right format for conversion */

validate_addr_form(user_supplied_addr);
addr = inet_addr(user_supplied_addr);
hp = gethostbyaddr( addr, sizeof(struct in_addr), AF_INET);
strcpy(hostname, hp->h_name);

}

If an attacker provides an address that appears to be well-formed, but the address does not resolve to a hostname, then the call to gethostbyaddr() will return NULL. Since the code does not check the return value from gethostbyaddr (CWE-252), a NULL pointer dereference (CWE-476) would then occur in the call to strcpy().

Note that this code is also vulnerable to a buffer overflow (CWE-119).

Example 8

In the following C/C++ example the method outputStringToFile opens a file in the local filesystem and outputs a string to the file. The input parameters output and filename contain the string to output to the file and the name of the file respectively.

(bad code)

Example Language: C++

int outputStringToFile(char *output, char *filename) {

openFileToWrite(filename);
writeToFile(output);
closeFile(filename);

}

However, this code does not check the return values of the methods openFileToWrite, writeToFile, closeFile to verify that the file was properly opened and closed and that the string was successfully written to the file. The return values for these methods should be checked to determine if the method was successful and allow for detection of errors or unexpected conditions as in the following example.

(good code)

Example Language: C++

int outputStringToFile(char *output, char *filename) {

int isOutput = SUCCESS;

int isOpen = openFileToWrite(filename);
if (isOpen == FAIL) {

printf("Unable to open file %s", filename);
isOutput = FAIL;

}
else {

int isWrite = writeToFile(output);
if (isWrite == FAIL) {

printf("Unable to write to file %s", filename);
isOutput = FAIL;

}

int isClose = closeFile(filename);
if (isClose == FAIL)

isOutput = FAIL;

}
return isOutput;

}

Example 9

In the following Java example the method readFromFile uses a FileReader object to read the contents of a file. The FileReader object is created using the File object readFile, the readFile object is initialized using the setInputFile method. The setInputFile method should be called before calling the readFromFile method.

(bad code)

Example Language: Java

private File readFile = null;

public void setInputFile(String inputFile) {

// create readFile File object from string containing name of file

}

public void readFromFile() {

try {

reader = new FileReader(readFile);

// read input file

} catch (FileNotFoundException ex) {...}

}

However, the readFromFile method does not check to see if the readFile object is null, i.e. has not been initialized, before creating the FileReader object and reading from the input file. The readFromFile method should verify whether the readFile object is null and output an error message and raise an exception if the readFile object is null, as in the following code.

(good code)

Example Language: Java

private File readFile = null;

public void setInputFile(String inputFile) {

// create readFile File object from string containing name of file

}

public void readFromFile() {

try {

if (readFile == null) {

System.err.println("Input file has not been set, call setInputFile method before calling openInputFile");
throw NullPointerException;

}

reader = new FileReader(readFile);

// read input file

} catch (FileNotFoundException ex) {...}
catch (NullPointerException ex) {...}

}

Observed Examples

Reference	Description
CVE-2023-49286	Chain: function in web caching proxy does not correctly check a return value (CWE-253) leading to a reachable assertion (CWE-617)
CVE-2007-3798	Unchecked return value leads to resultant integer overflow and code execution.
CVE-2006-4447	Program does not check return value when invoking functions to drop privileges, which could leave users with higher privileges than expected by forcing those functions to fail.
CVE-2006-2916	Program does not check return value when invoking functions to drop privileges, which could leave users with higher privileges than expected by forcing those functions to fail.

Potential Mitigations

Phase: Requirements

Strategy: Language Selection

Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.

Choose languages with features such as exception handling that force the programmer to anticipate unusual conditions that may generate exceptions. Custom exceptions may need to be developed to handle unusual business-logic conditions. Be careful not to pass sensitive exceptions back to the user (CWE-209, CWE-248).

Phase: Implementation

Check the results of all functions that return a value and verify that the value is expected.

Effectiveness: High

Note: Checking the return value of the function will typically be sufficient, however beware of race conditions (CWE-362) in a concurrent environment.

Phase: Implementation

If using exception handling, catch and throw specific exceptions instead of overly-general exceptions (CWE-396, CWE-397). Catch and handle exceptions as locally as possible so that exceptions do not propagate too far up the call stack (CWE-705). Avoid unchecked or uncaught exceptions where feasible (CWE-248).

Effectiveness: High

Note: Using specific exceptions, and ensuring that exceptions are checked, helps programmers to anticipate and appropriately handle many unusual events that could occur.

Phase: Implementation

Ensure that error messages only contain minimal details that are useful to the intended audience and no one else. The messages need to strike the balance between being too cryptic (which can confuse users) or being too detailed (which may reveal more than intended). The messages should not reveal the methods that were used to determine the error. Attackers can use detailed information to refine or optimize their original attack, thereby increasing their chances of success.

If errors must be captured in some detail, record them in log messages, but consider what could occur if the log messages can be viewed by attackers. Highly sensitive information such as passwords should never be saved to log files.

Avoid inconsistent messaging that might accidentally tip off an attacker about internal state, such as whether a user account exists or not.

Exposing additional information to a potential attacker in the context of an exceptional condition can help the attacker determine what attack vectors are most likely to succeed beyond DoS.

Phase: Implementation

Strategy: Input Validation

Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.

When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue."

Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.

Note: Performing extensive input validation does not help with handling unusual conditions, but it will minimize their occurrences and will make it more difficult for attackers to trigger them.

Phases: Architecture and Design; Implementation

If the program must fail, ensure that it fails gracefully (fails closed). There may be a temptation to simply let the program fail poorly in cases such as low memory conditions, but an attacker may be able to assert control before the software has fully exited. Alternately, an uncontrolled failure could cause cascading problems with other downstream components; for example, the program could send a signal to a downstream process so the process immediately knows that a problem has occurred and has a better chance of recovery.

Phase: Architecture and Design

Use system limits, which should help to prevent resource exhaustion. However, the product should still handle low resource conditions since they may still occur.

Detection Methods

Automated Static Analysis

Automated static analysis may be useful for detecting unusual conditions involving system resources or common programming idioms, but not for violations of business rules.

Effectiveness: Moderate

Manual Dynamic Analysis

Identify error conditions that are not likely to occur during normal usage and trigger them. For example, run the program under low memory conditions, run with insufficient privileges or permissions, interrupt a transaction before it is completed, or disable connectivity to basic network services such as DNS. Monitor the software for any unexpected behavior. If you trigger an unhandled exception or similar error that was discovered and handled by the application's environment, it may still indicate unexpected conditions that were not handled by the application itself.

Memberships

Nature	Type	ID	Name
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	742	CERT C Secure Coding Standard (2008) Chapter 9 - Memory Management (MEM)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	802	2010 Top 25 - Risky Resource Management
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	867	2011 Top 25 - Weaknesses On the Cusp
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	876	CERT C++ Secure Coding Section 08 - Memory Management (MEM)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	880	CERT C++ Secure Coding Section 12 - Exceptions and Error Handling (ERR)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	962	SFP Secondary Cluster: Unchecked Status Condition
MemberOf	View - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries).	1003	Weaknesses for Simplified Mapping of Published Vulnerabilities
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1141	SEI CERT Oracle Secure Coding Standard for Java - Guidelines 07. Exceptional Behavior (ERR)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1181	SEI CERT Perl Coding Standard - Guidelines 03. Expressions (EXP)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1364	ICS Communications: Zone Boundary Failures
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1405	Comprehensive Categorization: Improper Check or Handling of Exceptional Conditions

Vulnerability Mapping Notes

Usage: ALLOWED-WITH-REVIEW

(this CWE ID could be used to map to real-world vulnerabilities in limited situations requiring careful review)

Reason: Abstraction

Rationale:

This CWE entry is a Class and might have Base-level children that would be more appropriate

Comments:

Examine children of this entry to see if there is a better fit

Notes

Relationship

Sometimes, when a return value can be used to indicate an error, an unchecked return value is a code-layer instance of a missing application-layer check for exceptional conditions. However, return values are not always needed to communicate exceptional conditions. For example, expiration of resources, values passed by reference, asynchronously modified data, sockets, etc. may indicate exceptional conditions without the use of a return value.

Taxonomy Mappings

Mapped Taxonomy Name	Node ID	Fit	Mapped Node Name
SEI CERT Perl Coding Standard	EXP31-PL	CWE More Abstract	Do not suppress or ignore exceptions
ISA/IEC 62443	Part 4-2		Req CR 3.5
ISA/IEC 62443	Part 4-2		Req CR 3.7

References

[REF-62] Mark Dowd, John McDonald and Justin Schuh. "The Art of Software Security Assessment". Chapter 7, "Program Building Blocks" Page 341. 1st Edition. Addison Wesley. 2006.

[REF-62] Mark Dowd, John McDonald and Justin Schuh. "The Art of Software Security Assessment". Chapter 1, "Exceptional Conditions," Page 22. 1st Edition. Addison Wesley. 2006.

[REF-44] Michael Howard, David LeBlanc and John Viega. "24 Deadly Sins of Software Security". "Sin 11: Failure to Handle Errors Correctly." Page 183. McGraw-Hill. 2010.

[REF-622] Frank Kim. "Top 25 Series - Rank 15 - Improper Check for Unusual or Exceptional Conditions". SANS Software Security Institute. 2010-03-15. <https://www.sans.org/blog/top-25-series-rank-15-improper-check-for-unusual-or-exceptional-conditions/>. URL validated: 2023-04-07.

Content History

Submissions
Submission Date	Submitter	Organization
2009-03-03 (CWE 1.3, 2009-03-10)	CWE Content Team	MITRE
2009-03-03 (CWE 1.3, 2009-03-10)	New entry for reorganization of CWE-703.
Contributions
Contribution Date	Contributor	Organization
2023-04-25	"Mapping CWE to 62443" Sub-Working Group	CWE-CAPEC ICS/OT SIG
2023-04-25	Suggested mappings to ISA/IEC 62443.
Modifications
Modification Date	Modifier	Organization
2009-07-27	CWE Content Team	MITRE
2009-07-27	updated Relationships
2009-12-28	CWE Content Team	MITRE
2009-12-28	updated Applicable_Platforms, Likelihood_of_Exploit, Time_of_Introduction
2010-02-16	CWE Content Team	MITRE
2010-02-16	updated Background_Details, Common_Consequences, Demonstrative_Examples, Description, Detection_Factors, Name, Observed_Examples, Potential_Mitigations, References, Related_Attack_Patterns, Relationship_Notes, Relationships
2010-04-05	CWE Content Team	MITRE
2010-04-05	updated Demonstrative_Examples, Related_Attack_Patterns
2010-06-21	CWE Content Team	MITRE
2010-06-21	updated Common_Consequences, Detection_Factors, Potential_Mitigations, References
2010-09-27	CWE Content Team	MITRE
2010-09-27	updated Potential_Mitigations
2010-12-13	CWE Content Team	MITRE
2010-12-13	updated Relationship_Notes
2011-03-29	CWE Content Team	MITRE
2011-03-29	updated Description, Relationships
2011-06-01	CWE Content Team	MITRE
2011-06-01	updated Common_Consequences
2011-06-27	CWE Content Team	MITRE
2011-06-27	updated Common_Consequences, Related_Attack_Patterns, Relationships
2011-09-13	CWE Content Team	MITRE
2011-09-13	updated Relationships, Taxonomy_Mappings
2012-05-11	CWE Content Team	MITRE
2012-05-11	updated Relationships
2012-10-30	CWE Content Team	MITRE
2012-10-30	updated Potential_Mitigations
2013-02-21	CWE Content Team	MITRE
2013-02-21	updated Relationships
2014-07-30	CWE Content Team	MITRE
2014-07-30	updated Demonstrative_Examples, Relationships
2015-12-07	CWE Content Team	MITRE
2015-12-07	updated Relationships
2017-01-19	CWE Content Team	MITRE
2017-01-19	updated Relationships
2017-11-08	CWE Content Team	MITRE
2017-11-08	updated Modes_of_Introduction, References, Relationships, Taxonomy_Mappings
2019-01-03	CWE Content Team	MITRE
2019-01-03	updated Relationships, Taxonomy_Mappings
2019-06-20	CWE Content Team	MITRE
2019-06-20	updated Description, Relationships
2020-02-24	CWE Content Team	MITRE
2020-02-24	updated Potential_Mitigations, Relationships
2020-06-25	CWE Content Team	MITRE
2020-06-25	updated Potential_Mitigations
2020-12-10	CWE Content Team	MITRE
2020-12-10	updated Potential_Mitigations
2021-03-15	CWE Content Team	MITRE
2021-03-15	updated Demonstrative_Examples, Relationships
2021-07-20	CWE Content Team	MITRE
2021-07-20	updated Relationships
2022-04-28	CWE Content Team	MITRE
2022-04-28	updated Relationships
2023-01-31	CWE Content Team	MITRE
2023-01-31	updated Description, Potential_Mitigations
2023-04-27	CWE Content Team	MITRE
2023-04-27	updated References, Relationships, Taxonomy_Mappings
2023-06-29	CWE Content Team	MITRE
2023-06-29	updated Mapping_Notes
2024-02-29 (CWE 4.14, 2024-02-29)	CWE Content Team	MITRE
2024-02-29 (CWE 4.14, 2024-02-29)	updated Observed_Examples
Previous Entry Names
Change Date	Previous Entry Name
2010-02-16	Improper Check for Exceptional Conditions

Weakness ID: 460

View customized information:

Description

The product does not clean up its state or incorrectly cleans up its state when an exception is thrown, leading to unexpected state or control flow.

Extended Description

Often, when functions or loops become complicated, some level of resource cleanup is needed throughout execution. Exceptions can disturb the flow of the code and prevent the necessary cleanup from happening.

Relationships

Relevant to the view "Research Concepts" (CWE-1000)

Nature	Type	ID	Name
ChildOf	Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource.	755	Improper Handling of Exceptional Conditions
ChildOf	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	459	Incomplete Cleanup

Relevant to the view "Architectural Concepts" (CWE-1008)

Nature	Type	ID	Name
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1012	Cross Cutting

Modes Of Introduction

Phase	Note
Implementation	REALIZATION: This weakness is caused during implementation of an architectural security tactic.

Applicable Platforms

Languages

C (Undetermined Prevalence)

C++ (Undetermined Prevalence)

Java (Undetermined Prevalence)

C# (Undetermined Prevalence)

Common Consequences

Scope	Impact	Likelihood
Other	Technical Impact: Varies by Context The code could be left in a bad state.

Likelihood Of Exploit

Medium

Demonstrative Examples

Example 1

The following example demonstrates the weakness.

(bad code)

Example Language: Java

public class foo {

public static final void main( String args[] ) {

boolean returnValue;
returnValue=doStuff();

}
public static final boolean doStuff( ) {

boolean threadLock;
boolean truthvalue=true;
try {

while(
//check some condition
) {

threadLock=true; //do some stuff to truthvalue
threadLock=false;

}

}
catch (Exception e){

System.err.println("You did something bad");
if (something) return truthvalue;

}
return truthvalue;

}

In this case, a thread might be left locked accidentally.

Potential Mitigations

Phase: Implementation

If one breaks from a loop or function by throwing an exception, make sure that cleanup happens or that you should exit the program. Use throwing exceptions sparsely.

Detection Methods

Automated Static Analysis

Effectiveness: High

Memberships

Nature	Type	ID	Name
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	851	The CERT Oracle Secure Coding Standard for Java (2011) Chapter 8 - Exceptional Behavior (ERR)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	880	CERT C++ Secure Coding Section 12 - Exceptions and Error Handling (ERR)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	961	SFP Secondary Cluster: Incorrect Exception Behavior
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1141	SEI CERT Oracle Secure Coding Standard for Java - Guidelines 07. Exceptional Behavior (ERR)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1181	SEI CERT Perl Coding Standard - Guidelines 03. Expressions (EXP)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1416	Comprehensive Categorization: Resource Lifecycle Management

Vulnerability Mapping Notes

Usage: ALLOWED

(this CWE ID could be used to map to real-world vulnerabilities)

Reason: Acceptable-Use

Rationale:

This CWE entry is at the Base level of abstraction, which is a preferred level of abstraction for mapping to the root causes of vulnerabilities.

Comments:

Taxonomy Mappings

Mapped Taxonomy Name	Node ID	Fit	Mapped Node Name
CLASP			Improper cleanup on thrown exception
The CERT Oracle Secure Coding Standard for Java (2011)	ERR03-J		Restore prior object state on method failure
The CERT Oracle Secure Coding Standard for Java (2011)	ERR05-J		Do not let checked exceptions escape from a finally block
SEI CERT Perl Coding Standard	EXP31-PL	Imprecise	Do not suppress or ignore exceptions

References

[REF-18] Secure Software, Inc.. "The CLASP Application Security Process". 2005. <https://cwe.mitre.org/documents/sources/TheCLASPApplicationSecurityProcess.pdf>.

Content History

Submissions
Submission Date	Submitter	Organization
2006-07-19 (CWE Draft 3, 2006-07-19)	CLASP
2006-07-19 (CWE Draft 3, 2006-07-19)
Modifications
Modification Date	Modifier	Organization
2008-07-01	Eric Dalci	Cigital
2008-07-01	updated Time_of_Introduction
2008-09-08	CWE Content Team	MITRE
2008-09-08	updated Applicable_Platforms, Common_Consequences, Relationships, Other_Notes, Taxonomy_Mappings
2009-03-10	CWE Content Team	MITRE
2009-03-10	updated Relationships
2009-05-27	CWE Content Team	MITRE
2009-05-27	updated Description
2011-06-01	CWE Content Team	MITRE
2011-06-01	updated Common_Consequences, Relationships, Taxonomy_Mappings
2011-06-27	CWE Content Team	MITRE
2011-06-27	updated Common_Consequences
2011-09-13	CWE Content Team	MITRE
2011-09-13	updated Relationships, Taxonomy_Mappings
2012-05-11	CWE Content Team	MITRE
2012-05-11	updated Relationships
2014-06-23	CWE Content Team	MITRE
2014-06-23	updated Description, Other_Notes
2014-07-30	CWE Content Team	MITRE
2014-07-30	updated Relationships
2017-11-08	CWE Content Team	MITRE
2017-11-08	updated Demonstrative_Examples, Modes_of_Introduction, Relationships, Taxonomy_Mappings
2019-01-03	CWE Content Team	MITRE
2019-01-03	updated Relationships, Taxonomy_Mappings
2020-02-24	CWE Content Team	MITRE
2020-02-24	updated References, Type
2021-03-15	CWE Content Team	MITRE
2021-03-15	updated Relationships
2023-04-27	CWE Content Team	MITRE
2023-04-27	updated Detection_Factors, Relationships
2023-06-29	CWE Content Team	MITRE
2023-06-29	updated Mapping_Notes
2024-02-29 (CWE 4.14, 2024-02-29)	CWE Content Team	MITRE
2024-02-29 (CWE 4.14, 2024-02-29)	updated Demonstrative_Examples

Weakness ID: 116

View customized information:

Description

Extended Description

Improper encoding or escaping can allow attackers to change the commands that are sent to another component, inserting malicious commands instead.

Most products follow a certain protocol that uses structured messages for communication between components, such as queries or commands. These structured messages can contain raw data interspersed with metadata or control information. For example, "GET /index.html HTTP/1.1" is a structured message containing a command ("GET") with a single argument ("/index.html") and metadata about which protocol version is being used ("HTTP/1.1").

If an application uses attacker-supplied inputs to construct a structured message without properly encoding or escaping, then the attacker could insert special characters that will cause the data to be interpreted as control information or metadata. Consequently, the component that receives the output will perform the wrong operations, or otherwise interpret the data incorrectly.

Alternate Terms

Output Sanitization
Output Validation
Output Encoding

Relationships

Relevant to the view "Research Concepts" (CWE-1000)

Nature	Type	ID	Name
ChildOf	Pillar - a weakness that is the most abstract type of weakness and represents a theme for all class/base/variant weaknesses related to it. A Pillar is different from a Category as a Pillar is still technically a type of weakness that describes a mistake, while a Category represents a common characteristic used to group related things.	707	Improper Neutralization
ParentOf	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	117	Improper Output Neutralization for Logs
ParentOf	Variant - a weakness that is linked to a certain type of product, typically involving a specific language or technology. More specific than a Base weakness. Variant level weaknesses typically describe issues in terms of 3 to 5 of the following dimensions: behavior, property, technology, language, and resource.	644	Improper Neutralization of HTTP Headers for Scripting Syntax
ParentOf	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	838	Inappropriate Encoding for Output Context
CanPrecede	Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource.	74	Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')

Relevant to the view "Weaknesses for Simplified Mapping of Published Vulnerabilities" (CWE-1003)

Nature	Type	ID	Name
ParentOf	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	838	Inappropriate Encoding for Output Context

Modes Of Introduction

Phase	Note
Implementation
Operation

Applicable Platforms

Languages

Class: Not Language-Specific (Often Prevalent)

Technologies

Database Server (Often Prevalent)

Web Server (Often Prevalent)

Common Consequences

Scope	Impact	Likelihood
Integrity	Technical Impact: Modify Application Data The communications between components can be modified in unexpected ways. Unexpected commands can be executed, bypassing other security mechanisms. Incoming data can be misinterpreted.
Integrity Confidentiality Availability Access Control	Technical Impact: Execute Unauthorized Code or Commands The communications between components can be modified in unexpected ways. Unexpected commands can be executed, bypassing other security mechanisms. Incoming data can be misinterpreted.
Confidentiality	Technical Impact: Bypass Protection Mechanism The communications between components can be modified in unexpected ways. Unexpected commands can be executed, bypassing other security mechanisms. Incoming data can be misinterpreted.

Likelihood Of Exploit

High

Demonstrative Examples

Example 1

This code displays an email address that was submitted as part of a form.

(bad code)

Example Language: JSP

<% String email = request.getParameter("email"); %>
...
Email Address: <%= email %>

The value read from the form parameter is reflected back to the client browser without having been encoded prior to output, allowing various XSS attacks (CWE-79).

Example 2

Consider a chat application in which a front-end web application communicates with a back-end server. The back-end is legacy code that does not perform authentication or authorization, so the front-end must implement it. The chat protocol supports two commands, SAY and BAN, although only administrators can use the BAN command. Each argument must be separated by a single space. The raw inputs are URL-encoded. The messaging protocol allows multiple commands to be specified on the same line if they are separated by a "|" character.

First let's look at the back end command processor code

(bad code)

Example Language: Perl

$inputString = readLineFromFileHandle($serverFH);

# generate an array of strings separated by the "|" character.
@commands = split(/\|/, $inputString);

foreach $cmd (@commands) {

# separate the operator from its arguments based on a single whitespace
($operator, $args) = split(/ /, $cmd, 2);

$args = UrlDecode($args);
if ($operator eq "BAN") {

ExecuteBan($args);

}
elsif ($operator eq "SAY") {

ExecuteSay($args);

}

The front end web application receives a command, encodes it for sending to the server, performs the authorization check, and sends the command to the server.

(bad code)

Example Language: Perl

$inputString = GetUntrustedArgument("command");
($cmd, $argstr) = split(/\s+/, $inputString, 2);

# removes extra whitespace and also changes CRLF's to spaces
$argstr =~ s/\s+/ /gs;

$argstr = UrlEncode($argstr);
if (($cmd eq "BAN") && (! IsAdministrator($username))) {

die "Error: you are not the admin.\n";

}

# communicate with file server using a file handle
$fh = GetServerFileHandle("myserver");

print $fh "$cmd $argstr\n";

It is clear that, while the protocol and back-end allow multiple commands to be sent in a single request, the front end only intends to send a single command. However, the UrlEncode function could leave the "|" character intact. If an attacker provides:

(attack code)

SAY hello world|BAN user12

then the front end will see this is a "SAY" command, and the $argstr will look like "hello world | BAN user12". Since the command is "SAY", the check for the "BAN" command will fail, and the front end will send the URL-encoded command to the back end:

(result)

SAY hello%20world|BAN%20user12

The back end, however, will treat these as two separate commands:

(result)

SAY hello world
BAN user12

Notice, however, that if the front end properly encodes the "|" with "%7C", then the back end will only process a single command.

Example 3

This example takes user input, passes it through an encoding scheme and then creates a directory specified by the user.

(bad code)

Example Language: Perl

sub GetUntrustedInput {

return($ARGV[0]);

}

sub encode {

my($str) = @_;
$str =~ s/\&/\&/gs;
$str =~ s/\"/\"/gs;
$str =~ s/\'/\'/gs;
$str =~ s/\</\</gs;
$str =~ s/\>/\>/gs;
return($str);

}

sub doit {

my $uname = encode(GetUntrustedInput("username"));
print "<b>Welcome, $uname!</b><p>\n";
system("cd /home/$uname; /bin/ls -l");

}

The programmer attempts to encode dangerous characters, however the denylist for encoding is incomplete (CWE-184) and an attacker can still pass a semicolon, resulting in a chain with command injection (CWE-77).

Additionally, the encoding routine is used inappropriately with command execution. An attacker doesn't even need to insert their own semicolon. The attacker can instead leverage the encoding routine to provide the semicolon to separate the commands. If an attacker supplies a string of the form:

(attack code)

' pwd

then the program will encode the apostrophe and insert the semicolon, which functions as a command separator when passed to the system function. This allows the attacker to complete the command injection.

Observed Examples

Reference	Description
CVE-2021-41232	Chain: authentication routine in Go-based agile development product does not escape user name (CWE-116), allowing LDAP injection (CWE-90)
CVE-2008-4636	OS command injection in backup software using shell metacharacters in a filename; correct behavior would require that this filename could not be changed.
CVE-2008-0769	Web application does not set the charset when sending a page to a browser, allowing for XSS exploitation when a browser chooses an unexpected encoding.
CVE-2008-0005	Program does not set the charset when sending a page to a browser, allowing for XSS exploitation when a browser chooses an unexpected encoding.
CVE-2008-5573	SQL injection via password parameter; a strong password might contain "&"
CVE-2008-3773	Cross-site scripting in chat application via a message subject, which normally might contain "&" and other XSS-related characters.
CVE-2008-0757	Cross-site scripting in chat application via a message, which normally might be allowed to contain arbitrary content.

Potential Mitigations

Phase: Architecture and Design

Strategy: Libraries or Frameworks

Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.

For example, consider using the ESAPI Encoding control [REF-45] or a similar tool, library, or framework. These will help the programmer encode outputs in a manner less prone to error.

Alternately, use built-in functions, but consider using wrappers in case those functions are discovered to have a vulnerability.

Phase: Architecture and Design

Strategy: Parameterization

If available, use structured mechanisms that automatically enforce the separation between data and code. These mechanisms may be able to provide the relevant quoting, encoding, and validation automatically, instead of relying on the developer to provide this capability at every point where output is generated.

For example, stored procedures can enforce database query structure and reduce the likelihood of SQL injection.

Phases: Architecture and Design; Implementation

Understand the context in which your data will be used and the encoding that will be expected. This is especially important when transmitting data between different components, or when generating outputs that can contain multiple encodings at the same time, such as web pages or multi-part mail messages. Study all expected communication protocols and data representations to determine the required encoding strategies.

Phase: Architecture and Design

In some cases, input validation may be an important strategy when output encoding is not a complete solution. For example, you may be providing the same output that will be processed by multiple consumers that use different encodings or representations. In other cases, you may be required to allow user-supplied input to contain control information, such as limited HTML tags that support formatting in a wiki or bulletin board. When this type of requirement must be met, use an extremely strict allowlist to limit which control sequences can be used. Verify that the resulting syntactic structure is what you expect. Use your normal encoding methods for the remainder of the input.

Phase: Architecture and Design

Use input validation as a defense-in-depth measure to reduce the likelihood of output encoding errors (see CWE-20).

Phase: Requirements

Fully specify which encodings are required by components that will be communicating with each other.

Phase: Implementation

When exchanging data between components, ensure that both components are using the same character encoding. Ensure that the proper encoding is applied at each interface. Explicitly set the encoding you are using whenever the protocol allows you to do so.

Detection Methods

Automated Static Analysis

This weakness can often be detected using automated static analysis tools. Many modern tools use data flow analysis or constraint-based techniques to minimize the number of false positives.

Effectiveness: Moderate

Note: This is not a perfect solution, since 100% accuracy and coverage are not feasible.

Automated Dynamic Analysis

This weakness can be detected using dynamic tools and techniques that interact with the software using large test suites with many diverse inputs, such as fuzz testing (fuzzing), robustness testing, and fault injection. The software's operation may slow down, but it should not become unstable, crash, or generate incorrect results.

Memberships

Nature	Type	ID	Name
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	751	2009 Top 25 - Insecure Interaction Between Components
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	845	The CERT Oracle Secure Coding Standard for Java (2011) Chapter 2 - Input Validation and Data Sanitization (IDS)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	883	CERT C++ Secure Coding Section 49 - Miscellaneous (MSC)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	992	SFP Secondary Cluster: Faulty Input Transformation
MemberOf	View - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries).	1003	Weaknesses for Simplified Mapping of Published Vulnerabilities
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1134	SEI CERT Oracle Secure Coding Standard for Java - Guidelines 00. Input Validation and Data Sanitization (IDS)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1179	SEI CERT Perl Coding Standard - Guidelines 01. Input Validation and Data Sanitization (IDS)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1347	OWASP Top Ten 2021 Category A03:2021 - Injection
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1407	Comprehensive Categorization: Improper Neutralization

Vulnerability Mapping Notes

Usage: ALLOWED-WITH-REVIEW

(this CWE ID could be used to map to real-world vulnerabilities in limited situations requiring careful review)

Reason: Abstraction

Rationale:

This CWE entry is a Class and might have Base-level children that would be more appropriate

Comments:

Examine children of this entry to see if there is a better fit

Notes

Relationship

This weakness is primary to all weaknesses related to injection (CWE-74) since the inherent nature of injection involves the violation of structured messages.

Relationship

CWE-116 and CWE-20 have a close association because, depending on the nature of the structured message, proper input validation can indirectly prevent special characters from changing the meaning of a structured message. For example, by validating that a numeric ID field should only contain the 0-9 characters, the programmer effectively prevents injection attacks.

However, input validation is not always sufficient, especially when less stringent data types must be supported, such as free-form text. Consider a SQL injection scenario in which a last name is inserted into a query. The name "O'Reilly" would likely pass the validation step since it is a common last name in the English language. However, it cannot be directly inserted into the database because it contains the "'" apostrophe character, which would need to be escaped or otherwise neutralized. In this case, stripping the apostrophe might reduce the risk of SQL injection, but it would produce incorrect behavior because the wrong name would be recorded.

Terminology

The usage of the "encoding" and "escaping" terms varies widely. For example, in some programming languages, the terms are used interchangeably, while other languages provide APIs that use both terms for different tasks. This overlapping usage extends to the Web, such as the "escape" JavaScript function whose purpose is stated to be encoding. The concepts of encoding and escaping predate the Web by decades. Given such a context, it is difficult for CWE to adopt a consistent vocabulary that will not be misinterpreted by some constituency.

Theoretical

This is a data/directive boundary error in which data boundaries are not sufficiently enforced before it is sent to a different control sphere.

Research Gap

While many published vulnerabilities are related to insufficient output encoding, there is such an emphasis on input validation as a protection mechanism that the underlying causes are rarely described. Within CVE, the focus is primarily on well-understood issues like cross-site scripting and SQL injection. It is likely that this weakness frequently occurs in custom protocols that support multiple encodings, which are not necessarily detectable with automated techniques.

Taxonomy Mappings

Mapped Taxonomy Name	Node ID	Fit	Mapped Node Name
WASC	22		Improper Output Handling
The CERT Oracle Secure Coding Standard for Java (2011)	IDS00-J	Exact	Sanitize untrusted data passed across a trust boundary
The CERT Oracle Secure Coding Standard for Java (2011)	IDS05-J		Use a subset of ASCII for file and path names
SEI CERT Oracle Coding Standard for Java	IDS00-J	Imprecise	Prevent SQL injection
SEI CERT Perl Coding Standard	IDS33-PL	Exact	Sanitize untrusted data passed across a trust boundary

Related Attack Patterns

CAPEC-ID	Attack Pattern Name
CAPEC-104	Cross Zone Scripting
CAPEC-73	User-Controlled Filename
CAPEC-81	Web Server Logs Tampering
CAPEC-85	AJAX Footprinting

References

[REF-45] OWASP. "OWASP Enterprise Security API (ESAPI) Project". <http://www.owasp.org/index.php/ESAPI>.

[REF-46] Joshbw. "Output Sanitization". 2008-09-18. <https://web.archive.org/web/20081208054333/http://analyticalengine.net/archives/58>. URL validated: 2023-04-07.

[REF-47] Niyaz PK. "Sanitizing user data: How and where to do it". 2008-09-11. <https://web.archive.org/web/20090105222005/http://www.diovo.com/2008/09/sanitizing-user-data-how-and-where-to-do-it/>. URL validated: 2023-04-07.

[REF-48] Jeremiah Grossman. "Input validation or output filtering, which is better?". 2007-01-30. <https://blog.jeremiahgrossman.com/2007/01/input-validation-or-output-filtering.html>. URL validated: 2023-04-07.

[REF-49] Jim Manico. "Input Validation - Not That Important". 2008-08-10. <https://manicode.blogspot.com/2008/08/input-validation-not-that-important.html>. URL validated: 2023-04-07.

[REF-50] Michael Eddington. "Preventing XSS with Correct Output Encoding". <http://phed.org/2008/05/19/preventing-xss-with-correct-output-encoding/>.

[REF-7] Michael Howard and David LeBlanc. "Writing Secure Code". Chapter 11, "Canonical Representation Issues" Page 363. 2nd Edition. Microsoft Press. 2002-12-04. <https://www.microsoftpressstore.com/store/writing-secure-code-9780735617223>.

Content History

Submissions
Submission Date	Submitter	Organization
2006-07-19 (CWE Draft 3, 2006-07-19)	CWE Community
2006-07-19 (CWE Draft 3, 2006-07-19)	Submitted by members of the CWE community to extend early CWE versions
Modifications
Modification Date	Modifier	Organization
2008-07-01	Sean Eidemiller	Cigital
2008-07-01	added/updated demonstrative examples
2008-07-01	Eric Dalci	Cigital
2008-07-01	updated Time_of_Introduction
2008-09-08	CWE Content Team	MITRE
2008-09-08	updated Name, Relationships
2009-01-12	CWE Content Team	MITRE
2009-01-12	updated Alternate_Terms, Applicable_Platforms, Common_Consequences, Demonstrative_Examples, Description, Likelihood_of_Exploit, Name, Observed_Examples, Potential_Mitigations, References, Relationship_Notes, Relationships, Research_Gaps, Terminology_Notes, Theoretical_Notes
2009-03-10	CWE Content Team	MITRE
2009-03-10	updated Description, Potential_Mitigations
2009-05-27	CWE Content Team	MITRE
2009-05-27	updated Related_Attack_Patterns
2009-07-27	CWE Content Team	MITRE
2009-07-27	updated Demonstrative_Examples
2009-10-29	CWE Content Team	MITRE
2009-10-29	updated Relationships
2009-12-28	CWE Content Team	MITRE
2009-12-28	updated Demonstrative_Examples, Potential_Mitigations
2010-02-16	CWE Content Team	MITRE
2010-02-16	updated Detection_Factors, Potential_Mitigations, References, Taxonomy_Mappings
2010-04-05	CWE Content Team	MITRE
2010-04-05	updated Potential_Mitigations
2010-06-21	CWE Content Team	MITRE
2010-06-21	updated Potential_Mitigations
2011-03-29	CWE Content Team	MITRE
2011-03-29	updated Relationship_Notes, Relationships
2011-06-01	CWE Content Team	MITRE
2011-06-01	updated Common_Consequences, Relationships, Taxonomy_Mappings
2011-09-13	CWE Content Team	MITRE
2011-09-13	updated Relationships, Taxonomy_Mappings
2012-05-11	CWE Content Team	MITRE
2012-05-11	updated References, Relationships, Taxonomy_Mappings
2012-10-30	CWE Content Team	MITRE
2012-10-30	updated Potential_Mitigations
2014-06-23	CWE Content Team	MITRE
2014-06-23	updated References
2014-07-30	CWE Content Team	MITRE
2014-07-30	updated Demonstrative_Examples, Relationships
2015-12-07	CWE Content Team	MITRE
2015-12-07	updated Relationships
2017-01-19	CWE Content Team	MITRE
2017-01-19	updated Relationships
2017-05-03	CWE Content Team	MITRE
2017-05-03	updated Related_Attack_Patterns
2017-11-08	CWE Content Team	MITRE
2017-11-08	updated Applicable_Platforms, Common_Consequences, Demonstrative_Examples, Likelihood_of_Exploit, References, Taxonomy_Mappings
2018-03-27	CWE Content Team	MITRE
2018-03-27	updated References
2019-01-03	CWE Content Team	MITRE
2019-01-03	updated Relationships, Taxonomy_Mappings
2019-06-20	CWE Content Team	MITRE
2019-06-20	updated Relationships
2020-02-24	CWE Content Team	MITRE
2020-02-24	updated Relationships
2020-06-25	CWE Content Team	MITRE
2020-06-25	updated Applicable_Platforms, Demonstrative_Examples, Potential_Mitigations
2021-03-15	CWE Content Team	MITRE
2021-03-15	updated Relationships, Terminology_Notes
2021-10-28	CWE Content Team	MITRE
2021-10-28	updated Relationships
2022-10-13	CWE Content Team	MITRE
2022-10-13	updated Observed_Examples
2023-01-31	CWE Content Team	MITRE
2023-01-31	updated Description
2023-04-27	CWE Content Team	MITRE
2023-04-27	updated References, Relationships, Time_of_Introduction
2023-06-29	CWE Content Team	MITRE
2023-06-29	updated Mapping_Notes
Previous Entry Names
Change Date	Previous Entry Name
2008-04-11	Output Validation

2008-09-09	Incorrect Output Sanitization

2009-01-12	Insufficient Output Sanitization

Weakness ID: 22

View customized information:

Description

Extended Description

Many file operations are intended to take place within a restricted directory. By using special elements such as ".." and "/" separators, attackers can escape outside of the restricted location to access files or directories that are elsewhere on the system. One of the most common special elements is the "../" sequence, which in most modern operating systems is interpreted as the parent directory of the current location. This is referred to as relative path traversal. Path traversal also covers the use of absolute pathnames such as "/usr/local/bin", which may also be useful in accessing unexpected files. This is referred to as absolute path traversal.

In many programming languages, the injection of a null byte (the 0 or NUL) may allow an attacker to truncate a generated filename to widen the scope of attack. For example, the product may add ".txt" to any pathname, thus limiting the attacker to text files, but a null injection may effectively remove this restriction.

Alternate Terms

Directory traversal
Path traversal:	"Path traversal" is preferred over "directory traversal," but both terms are attack-focused.

Relationships

Relevant to the view "Research Concepts" (CWE-1000)

Nature	Type	ID	Name
ChildOf	Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource.	668	Exposure of Resource to Wrong Sphere
ChildOf	Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource.	706	Use of Incorrectly-Resolved Name or Reference
ParentOf	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	23	Relative Path Traversal
ParentOf	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	36	Absolute Path Traversal
CanFollow	Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource.	20	Improper Input Validation
CanFollow	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	73	External Control of File Name or Path
CanFollow	Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource.	172	Encoding Error

Relevant to the view "Software Development" (CWE-699)

Nature	Type	ID	Name
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1219	File Handling Issues

Relevant to the view "Weaknesses for Simplified Mapping of Published Vulnerabilities" (CWE-1003)

Nature	Type	ID	Name
ChildOf	Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource.	706	Use of Incorrectly-Resolved Name or Reference

Relevant to the view "CISQ Quality Measures (2020)" (CWE-1305)

Nature	Type	ID	Name
ParentOf	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	23	Relative Path Traversal
ParentOf	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	36	Absolute Path Traversal

Relevant to the view "CISQ Data Protection Measures" (CWE-1340)

Nature	Type	ID	Name
ParentOf	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	23	Relative Path Traversal
ParentOf	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	36	Absolute Path Traversal

Modes Of Introduction

Phase	Note
Implementation

Applicable Platforms

Languages

Class: Not Language-Specific (Undetermined Prevalence)

Common Consequences

Scope	Impact	Likelihood
Integrity Confidentiality Availability	Technical Impact: Execute Unauthorized Code or Commands The attacker may be able to create or overwrite critical files that are used to execute code, such as programs or libraries.
Integrity	Technical Impact: Modify Files or Directories The attacker may be able to overwrite or create critical files, such as programs, libraries, or important data. If the targeted file is used for a security mechanism, then the attacker may be able to bypass that mechanism. For example, appending a new account at the end of a password file may allow an attacker to bypass authentication.
Confidentiality	Technical Impact: Read Files or Directories The attacker may be able read the contents of unexpected files and expose sensitive data. If the targeted file is used for a security mechanism, then the attacker may be able to bypass that mechanism. For example, by reading a password file, the attacker could conduct brute force password guessing attacks in order to break into an account on the system.
Availability	Technical Impact: DoS: Crash, Exit, or Restart The attacker may be able to overwrite, delete, or corrupt unexpected critical files such as programs, libraries, or important data. This may prevent the product from working at all and in the case of a protection mechanisms such as authentication, it has the potential to lockout every user of the product.

Likelihood Of Exploit

High

Demonstrative Examples

Example 1

The following code could be for a social networking application in which each user's profile information is stored in a separate file. All files are stored in a single directory.

(bad code)

Example Language: Perl

my $dataPath = "/users/cwe/profiles";
my $username = param("user");
my $profilePath = $dataPath . "/" . $username;

open(my $fh, "<", $profilePath) || ExitError("profile read error: $profilePath");
print "<ul>\n";
while (<$fh>) {

print "<li>$_</li>\n";

}
print "</ul>\n";

While the programmer intends to access files such as "/users/cwe/profiles/alice" or "/users/cwe/profiles/bob", there is no verification of the incoming user parameter. An attacker could provide a string such as:

(attack code)

../../../etc/passwd

The program would generate a profile pathname like this:

(result)

/users/cwe/profiles/../../../etc/passwd

When the file is opened, the operating system resolves the "../" during path canonicalization and actually accesses this file:

(result)

/etc/passwd

As a result, the attacker could read the entire text of the password file.

Notice how this code also contains an error message information leak (CWE-209) if the user parameter does not produce a file that exists: the full pathname is provided. Because of the lack of output encoding of the file that is retrieved, there might also be a cross-site scripting problem (CWE-79) if profile contains any HTML, but other code would need to be examined.

Example 2

In the example below, the path to a dictionary file is read from a system property and used to initialize a File object.

(bad code)

Example Language: Java

String filename = System.getProperty("com.domain.application.dictionaryFile");
File dictionaryFile = new File(filename);

However, the path is not validated or modified to prevent it from containing relative or absolute path sequences before creating the File object. This allows anyone who can control the system property to determine what file is used. Ideally, the path should be resolved relative to some kind of application or user home directory.

Example 3

The following code takes untrusted input and uses a regular expression to filter "../" from the input. It then appends this result to the /home/user/ directory and attempts to read the file in the final resulting path.

(bad code)

Example Language: Perl

my $Username = GetUntrustedInput();
$Username =~ s/\.\.\///;
my $filename = "/home/user/" . $Username;
ReadAndSendFile($filename);

Since the regular expression does not have the /g global match modifier, it only removes the first instance of "../" it comes across. So an input value such as:

(attack code)

../../../etc/passwd

will have the first "../" stripped, resulting in:

(result)

../../etc/passwd

This value is then concatenated with the /home/user/ directory:

(result)

/home/user/../../etc/passwd

which causes the /etc/passwd file to be retrieved once the operating system has resolved the ../ sequences in the pathname. This leads to relative path traversal (CWE-23).

Example 4

The following code attempts to validate a given input path by checking it against an allowlist and once validated delete the given file. In this specific case, the path is considered valid if it starts with the string "/safe_dir/".

(bad code)

Example Language: Java

String path = getInputPath();
if (path.startsWith("/safe_dir/"))
{

File f = new File(path);
f.delete()

}

An attacker could provide an input such as this:

(attack code)

/safe_dir/../important.dat

The software assumes that the path is valid because it starts with the "/safe_path/" sequence, but the "../" sequence will cause the program to delete the important.dat file in the parent directory

Example 5

The following code demonstrates the unrestricted upload of a file with a Java servlet and a path traversal vulnerability. The action attribute of an HTML form is sending the upload file request to the Java servlet.

(good code)

Example Language: HTML

<form action="FileUploadServlet" method="post" enctype="multipart/form-data">

Choose a file to upload:
<input type="file" name="filename"/>
<br/>
<input type="submit" name="submit" value="Submit"/>

</form>

When submitted the Java servlet's doPost method will receive the request, extract the name of the file from the Http request header, read the file contents from the request and output the file to the local upload directory.

(bad code)

Example Language: Java

public class FileUploadServlet extends HttpServlet {

...

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

response.setContentType("text/html");
PrintWriter out = response.getWriter();
String contentType = request.getContentType();

// the starting position of the boundary header
int ind = contentType.indexOf("boundary=");
String boundary = contentType.substring(ind+9);

String pLine = new String();
String uploadLocation = new String(UPLOAD_DIRECTORY_STRING); //Constant value

// verify that content type is multipart form data
if (contentType != null && contentType.indexOf("multipart/form-data") != -1) {

// extract the filename from the Http header
BufferedReader br = new BufferedReader(new InputStreamReader(request.getInputStream()));
...
pLine = br.readLine();
String filename = pLine.substring(pLine.lastIndexOf("\\"), pLine.lastIndexOf("\""));
...

// output the file to the local upload directory
try {

BufferedWriter bw = new BufferedWriter(new FileWriter(uploadLocation+filename, true));
for (String line; (line=br.readLine())!=null; ) {

if (line.indexOf(boundary) == -1) {

bw.write(line);
bw.newLine();
bw.flush();

}

} //end of for loop
bw.close();

} catch (IOException ex) {...}
// output successful upload response HTML page

}
// output unsuccessful upload response HTML page
else
{...}

}

...

}

This code does not perform a check on the type of the file being uploaded (CWE-434). This could allow an attacker to upload any executable file or other file with malicious code.

Additionally, the creation of the BufferedWriter object is subject to relative path traversal (CWE-23). Since the code does not check the filename that is provided in the header, an attacker can use "../" sequences to write to files outside of the intended directory. Depending on the executing environment, the attacker may be able to specify arbitrary files to write to, leading to a wide variety of consequences, from code execution, XSS (CWE-79), or system crash.

Example 6

This script intends to read a user-supplied file from the current directory. The user inputs the relative path to the file and the script uses Python's os.path.join() function to combine the path to the current working directory with the provided path to the specified file. This results in an absolute path to the desired file. If the file does not exist when the script attempts to read it, an error is printed to the user.

(bad code)

Example Language: Python

import os
import sys
def main():

filename = sys.argv[1]
path = os.path.join(os.getcwd(), filename)
try:

with open(path, 'r') as f:

file_data = f.read()

except FileNotFoundError as e:

print("Error - file not found")

main()

However, if the user supplies an absolute path, the os.path.join() function will discard the path to the current working directory and use only the absolute path provided. For example, if the current working directory is /home/user/documents, but the user inputs /etc/passwd, os.path.join() will use only /etc/passwd, as it is considered an absolute path. In the above scenario, this would cause the script to access and read the /etc/passwd file.

(good code)

Example Language: Python

import os
import sys
def main():

filename = sys.argv[1]
path = os.path.normpath(f"{os.getcwd()}{os.sep}{filename}")
try:

with open(path, 'r') as f:

file_data = f.read()

except FileNotFoundError as e:

print("Error - file not found")

main()

The constructed path string uses os.sep to add the appropriate separation character for the given operating system (e.g. '\' or '/') and the call to os.path.normpath() removes any additional slashes that may have been entered - this may occur particularly when using a Windows path. By putting the pieces of the path string together in this fashion, the script avoids a call to os.path.join() and any potential issues that might arise if an absolute path is entered. With this version of the script, if the current working directory is /home/user/documents, and the user inputs /etc/passwd, the resulting path will be /home/user/documents/etc/passwd. The user is therefore contained within the current working directory as intended.

Observed Examples

Reference	Description
CVE-2022-45918	Chain: a learning management tool debugger uses external input to locate previous session logs (CWE-73) and does not properly validate the given path (CWE-20), allowing for filesystem path traversal using "../" sequences (CWE-24)
CVE-2019-20916	Python package manager does not correctly restrict the filename specified in a Content-Disposition header, allowing arbitrary file read using path traversal sequences such as "../"
CVE-2022-31503	Python package constructs filenames using an unsafe os.path.join call on untrusted input, allowing absolute path traversal because os.path.join resets the pathname to an absolute path that is specified as part of the input.
CVE-2022-24877	directory traversal in Go-based Kubernetes operator app allows accessing data from the controller's pod file system via ../ sequences in a yaml file
CVE-2021-21972	Chain: Cloud computing virtualization platform does not require authentication for upload of a tar format file (CWE-306), then uses .. path traversal sequences (CWE-23) in the file to access unexpected files, as exploited in the wild per CISA KEV.
CVE-2020-4053	a Kubernetes package manager written in Go allows malicious plugins to inject path traversal sequences into a plugin archive ("Zip slip") to copy a file outside the intended directory
CVE-2020-3452	Chain: security product has improper input validation (CWE-20) leading to directory traversal (CWE-22), as exploited in the wild per CISA KEV.
CVE-2019-10743	Go-based archive library allows extraction of files to locations outside of the target folder with "../" path traversal sequences in filenames in a zip file, aka "Zip Slip"
CVE-2010-0467	Newsletter module allows reading arbitrary files using "../" sequences.
CVE-2006-7079	Chain: PHP app uses extract for register_globals compatibility layer (CWE-621), enabling path traversal (CWE-22)
CVE-2009-4194	FTP server allows deletion of arbitrary files using ".." in the DELE command.
CVE-2009-4053	FTP server allows creation of arbitrary directories using ".." in the MKD command.
CVE-2009-0244	FTP service for a Bluetooth device allows listing of directories, and creation or reading of files using ".." sequences.
CVE-2009-4013	Software package maintenance program allows overwriting arbitrary files using "../" sequences.
CVE-2009-4449	Bulletin board allows attackers to determine the existence of files using the avatar.
CVE-2009-4581	PHP program allows arbitrary code execution using ".." in filenames that are fed to the include() function.
CVE-2010-0012	Overwrite of files using a .. in a Torrent file.
CVE-2010-0013	Chat program allows overwriting files using a custom smiley request.
CVE-2008-5748	Chain: external control of values for user's desired language and theme enables path traversal.
CVE-2009-1936	Chain: library file sends a redirect if it is directly requested but continues to execute, allowing remote file inclusion and path traversal.

Potential Mitigations

Phase: Implementation

Strategy: Input Validation

When validating filenames, use stringent allowlists that limit the character set to be used. If feasible, only allow a single "." character in the filename to avoid weaknesses such as CWE-23, and exclude directory separators such as "/" to avoid CWE-36. Use a list of allowable file extensions, which will help to avoid CWE-434.

Do not rely exclusively on a filtering mechanism that removes potentially dangerous characters. This is equivalent to a denylist, which may be incomplete (CWE-184). For example, filtering "/" is insufficient protection if the filesystem also supports the use of "\" as a directory separator. Another possible error could occur when the filtering is applied in a way that still produces dangerous data (CWE-182). For example, if "../" sequences are removed from the ".../...//" string in a sequential fashion, two instances of "../" would be removed from the original string, but the remaining characters would still form the "../" string.

Phase: Architecture and Design

For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks entirely. Then, these modified values would be submitted to the server.

Phase: Implementation

Strategy: Input Validation

Inputs should be decoded and canonicalized to the application's current internal representation before being validated (CWE-180). Make sure that the application does not decode the same input twice (CWE-174). Such errors could be used to bypass allowlist validation schemes by introducing dangerous inputs after they have been checked.

Use a built-in path canonicalization function (such as realpath() in C) that produces the canonical version of the pathname, which effectively removes ".." sequences and symbolic links (CWE-23, CWE-59). This includes:

realpath() in C

getCanonicalPath() in Java

GetFullPath() in ASP.NET

realpath() or abs_path() in Perl

realpath() in PHP

Phase: Architecture and Design

Strategy: Libraries or Frameworks

Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.

Phase: Operation

Strategy: Firewall

Use an application firewall that can detect attacks against this weakness. It can be beneficial in cases in which the code cannot be fixed (because it is controlled by a third party), as an emergency prevention measure while more comprehensive software assurance measures are applied, or to provide defense in depth.

Effectiveness: Moderate

Note: An application firewall might not cover all possible input vectors. In addition, attack techniques might be available to bypass the protection mechanism, such as using malformed inputs that can still be processed by the component that receives those inputs. Depending on functionality, an application firewall might inadvertently reject or modify legitimate requests. Finally, some manual effort may be required for customization.

Phases: Architecture and Design; Operation

Strategy: Environment Hardening

Run your code using the lowest privileges that are required to accomplish the necessary tasks [REF-76]. If possible, create isolated accounts with limited privileges that are only used for a single task. That way, a successful attack will not immediately give the attacker access to the rest of the software or its environment. For example, database applications rarely need to run as the database administrator, especially in day-to-day operations.

Phase: Architecture and Design

Strategy: Enforcement by Conversion

When the set of acceptable objects, such as filenames or URLs, is limited or known, create a mapping from a set of fixed input values (such as numeric IDs) to the actual filenames or URLs, and reject all other inputs.

For example, ID 1 could map to "inbox.txt" and ID 2 could map to "profile.txt". Features such as the ESAPI AccessReferenceMap [REF-185] provide this capability.

Phases: Architecture and Design; Operation

Strategy: Sandbox or Jail

Run the code in a "jail" or similar sandbox environment that enforces strict boundaries between the process and the operating system. This may effectively restrict which files can be accessed in a particular directory or which commands can be executed by the software.

OS-level examples include the Unix chroot jail, AppArmor, and SELinux. In general, managed code may provide some protection. For example, java.io.FilePermission in the Java SecurityManager allows the software to specify restrictions on file operations.

This may not be a feasible solution, and it only limits the impact to the operating system; the rest of the application may still be subject to compromise.

Be careful to avoid CWE-243 and other weaknesses related to jails.

Effectiveness: Limited

Note: The effectiveness of this mitigation depends on the prevention capabilities of the specific sandbox or jail being used and might only help to reduce the scope of an attack, such as restricting the attacker to certain system calls or limiting the portion of the file system that can be accessed.

Phases: Architecture and Design; Operation

Strategy: Attack Surface Reduction

Store library, include, and utility files outside of the web document root, if possible. Otherwise, store them in a separate directory and use the web server's access control capabilities to prevent attackers from directly requesting them. One common practice is to define a fixed constant in each calling program, then check for the existence of the constant in the library/include file; if the constant does not exist, then the file was directly requested, and it can exit immediately.

This significantly reduces the chance of an attacker being able to bypass any protection mechanisms that are in the base program but not in the include files. It will also reduce the attack surface.

Phase: Implementation

Avoid inconsistent messaging that might accidentally tip off an attacker about internal state, such as whether a user account exists or not.

In the context of path traversal, error messages which disclose path information can help attackers craft the appropriate attack strings to move through the file system hierarchy.

Phases: Operation; Implementation

Strategy: Environment Hardening

When using PHP, configure the application so that it does not use register_globals. During implementation, develop the application so that it does not rely on this feature, but be wary of implementing a register_globals emulation that is subject to weaknesses such as CWE-95, CWE-621, and similar issues.

Weakness Ordinalities

Ordinality	Description
Primary	(where the weakness exists independent of other weaknesses)
Resultant	(where the weakness is typically related to the presence of some other weaknesses)

Detection Methods

Automated Static Analysis

Automated techniques can find areas where path traversal weaknesses exist. However, tuning or customization may be required to remove or de-prioritize path-traversal problems that are only exploitable by the product's administrator - or other privileged users - and thus potentially valid behavior or, at worst, a bug instead of a vulnerability.

Effectiveness: High

Manual Static Analysis

Manual white box techniques may be able to provide sufficient code coverage and reduction of false positives if all file access operations can be assessed within limited time constraints.

Effectiveness: High

Automated Static Analysis - Binary or Bytecode

According to SOAR, the following detection techniques may be useful:

Highly cost effective:

Bytecode Weakness Analysis - including disassembler + source code weakness analysis

Cost effective for partial coverage:

Binary Weakness Analysis - including disassembler + source code weakness analysis

Effectiveness: High

Manual Static Analysis - Binary or Bytecode

According to SOAR, the following detection techniques may be useful:

Cost effective for partial coverage:

Binary / Bytecode disassembler - then use manual analysis for vulnerabilities & anomalies

Effectiveness: SOAR Partial

Dynamic Analysis with Automated Results Interpretation

According to SOAR, the following detection techniques may be useful:

Highly cost effective:

Web Application Scanner

Web Services Scanner

Database Scanners

Effectiveness: High

Dynamic Analysis with Manual Results Interpretation

According to SOAR, the following detection techniques may be useful:

Highly cost effective:

Fuzz Tester

Framework-based Fuzzer

Effectiveness: High

Manual Static Analysis - Source Code

According to SOAR, the following detection techniques may be useful:

Highly cost effective:

Manual Source Code Review (not inspections)

Cost effective for partial coverage:

Focused Manual Spotcheck - Focused manual analysis of source

Effectiveness: High

Automated Static Analysis - Source Code

According to SOAR, the following detection techniques may be useful:

Highly cost effective:

Source code Weakness Analyzer

Context-configured Source Code Weakness Analyzer

Effectiveness: High

Architecture or Design Review

According to SOAR, the following detection techniques may be useful:

Highly cost effective:

Formal Methods / Correct-By-Construction

Cost effective for partial coverage:

Inspection (IEEE 1028 standard) (can apply to requirements, design, source code, etc.)

Effectiveness: High

Functional Areas

File Processing

Affected Resources

File or Directory

Memberships

Nature	Type	ID	Name
MemberOf	View - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries).	635	Weaknesses Originally Used by NVD from 2008 to 2016
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	715	OWASP Top Ten 2007 Category A4 - Insecure Direct Object Reference
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	723	OWASP Top Ten 2004 Category A2 - Broken Access Control
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	743	CERT C Secure Coding Standard (2008) Chapter 10 - Input Output (FIO)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	802	2010 Top 25 - Risky Resource Management
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	813	OWASP Top Ten 2010 Category A4 - Insecure Direct Object References
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	865	2011 Top 25 - Risky Resource Management
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	877	CERT C++ Secure Coding Section 09 - Input Output (FIO)
MemberOf	View - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries).	884	CWE Cross-section
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	932	OWASP Top Ten 2013 Category A4 - Insecure Direct Object References
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	981	SFP Secondary Cluster: Path Traversal
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1031	OWASP Top Ten 2017 Category A5 - Broken Access Control
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1131	CISQ Quality Measures (2016) - Security
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1179	SEI CERT Perl Coding Standard - Guidelines 01. Input Validation and Data Sanitization (IDS)
MemberOf	View - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries).	1200	Weaknesses in the 2019 CWE Top 25 Most Dangerous Software Errors
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1308	CISQ Quality Measures - Security
MemberOf	View - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries).	1337	Weaknesses in the 2021 CWE Top 25 Most Dangerous Software Weaknesses
MemberOf	View - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries).	1340	CISQ Data Protection Measures
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1345	OWASP Top Ten 2021 Category A01:2021 - Broken Access Control
MemberOf	View - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries).	1350	Weaknesses in the 2020 CWE Top 25 Most Dangerous Software Weaknesses
MemberOf	View - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries).	1387	Weaknesses in the 2022 CWE Top 25 Most Dangerous Software Weaknesses
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1404	Comprehensive Categorization: File Handling
MemberOf	View - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries).	1425	Weaknesses in the 2023 CWE Top 25 Most Dangerous Software Weaknesses

Vulnerability Mapping Notes

Usage: ALLOWED

(this CWE ID could be used to map to real-world vulnerabilities)

Reason: Acceptable-Use

Rationale:

This CWE entry is at the Base level of abstraction, which is a preferred level of abstraction for mapping to the root causes of vulnerabilities.

Comments:

Notes

Relationship

Pathname equivalence can be regarded as a type of canonicalization error.

Relationship

Some pathname equivalence issues are not directly related to directory traversal, rather are used to bypass security-relevant checks for whether a file/directory can be accessed by the attacker (e.g. a trailing "/" on a filename could bypass access rules that don't expect a trailing /, causing a server to provide the file when it normally would not).

Terminology

Like other weaknesses, terminology is often based on the types of manipulations used, instead of the underlying weaknesses. Some people use "directory traversal" only to refer to the injection of ".." and equivalent sequences whose specific meaning is to traverse directories.

Other variants like "absolute pathname" and "drive letter" have the *effect* of directory traversal, but some people may not call it such, since it doesn't involve ".." or equivalent.

Research Gap

Many variants of path traversal attacks are probably under-studied with respect to root cause. CWE-790 and CWE-182 begin to cover part of this gap.

Research Gap

Incomplete diagnosis or reporting of vulnerabilities can make it difficult to know which variant is affected. For example, a researcher might say that "..\" is vulnerable, but not test "../" which may also be vulnerable.

Any combination of directory separators ("/", "\", etc.) and numbers of "." (e.g. "....") can produce unique variants; for example, the "//../" variant is not listed (CVE-2004-0325). See this entry's children and lower-level descendants.

Taxonomy Mappings

Mapped Taxonomy Name	Node ID	Fit	Mapped Node Name
PLOVER			Path Traversal
OWASP Top Ten 2007	A4	CWE More Specific	Insecure Direct Object Reference
OWASP Top Ten 2004	A2	CWE More Specific	Broken Access Control
CERT C Secure Coding	FIO02-C		Canonicalize path names originating from untrusted sources
SEI CERT Perl Coding Standard	IDS00-PL	Exact	Canonicalize path names before validating them
WASC	33		Path Traversal
Software Fault Patterns	SFP16		Path Traversal
OMG ASCSM	ASCSM-CWE-22

Related Attack Patterns

CAPEC-ID	Attack Pattern Name
CAPEC-126	Path Traversal
CAPEC-64	Using Slashes and URL Encoding Combined to Bypass Validation Logic
CAPEC-76	Manipulating Web Input to File System Calls
CAPEC-78	Using Escaped Slashes in Alternate Encoding
CAPEC-79	Using Slashes in Alternate Encoding

References

[REF-7] Michael Howard and David LeBlanc. "Writing Secure Code". Chapter 11, "Directory Traversal and Using Parent Paths (..)" Page 370. 2nd Edition. Microsoft Press. 2002-12-04. <https://www.microsoftpressstore.com/store/writing-secure-code-9780735617223>.

[REF-45] OWASP. "OWASP Enterprise Security API (ESAPI) Project". <http://www.owasp.org/index.php/ESAPI>.

[REF-185] OWASP. "Testing for Path Traversal (OWASP-AZ-001)". <http://www.owasp.org/index.php/Testing_for_Path_Traversal_(OWASP-AZ-001)>.

[REF-186] Johannes Ullrich. "Top 25 Series - Rank 7 - Path Traversal". SANS Software Security Institute. 2010-03-09. <https://www.sans.org/blog/top-25-series-rank-7-path-traversal/>. URL validated: 2023-04-07.

[REF-76] Sean Barnum and Michael Gegick. "Least Privilege". 2005-09-14. <https://web.archive.org/web/20211209014121/https://www.cisa.gov/uscert/bsi/articles/knowledge/principles/least-privilege>. URL validated: 2023-04-07.

[REF-62] Mark Dowd, John McDonald and Justin Schuh. "The Art of Software Security Assessment". Chapter 9, "Filenames and Paths", Page 503. 1st Edition. Addison Wesley. 2006.

[REF-962] Object Management Group (OMG). "Automated Source Code Security Measure (ASCSM)". ASCSM-CWE-22. 2016-01. <http://www.omg.org/spec/ASCSM/1.0/>.

Content History

Submissions
Submission Date	Submitter	Organization
2006-07-19 (CWE Draft 3, 2006-07-19)	PLOVER
2006-07-19 (CWE Draft 3, 2006-07-19)
Contributions
Contribution Date	Contributor	Organization
2022-07-11	Nick Johnston
2022-07-11	Identified weakness in Perl demonstrative example
Modifications
Modification Date	Modifier	Organization
2008-07-01	Eric Dalci	Cigital
2008-07-01	updated Potential_Mitigations, Time_of_Introduction
2008-08-15		Veracode
2008-08-15	Suggested OWASP Top Ten 2004 mapping
2008-09-08	CWE Content Team	MITRE
2008-09-08	updated Alternate_Terms, Relationships, Other_Notes, Relationship_Notes, Relevant_Properties, Taxonomy_Mappings, Weakness_Ordinalities
2008-10-14	CWE Content Team	MITRE
2008-10-14	updated Description
2008-11-24	CWE Content Team	MITRE
2008-11-24	updated Relationships, Taxonomy_Mappings
2009-07-27	CWE Content Team	MITRE
2009-07-27	updated Potential_Mitigations
2010-02-16	CWE Content Team	MITRE
2010-02-16	updated Alternate_Terms, Applicable_Platforms, Common_Consequences, Demonstrative_Examples, Description, Detection_Factors, Likelihood_of_Exploit, Name, Observed_Examples, Other_Notes, Potential_Mitigations, References, Related_Attack_Patterns, Relationship_Notes, Relationships, Research_Gaps, Taxonomy_Mappings, Terminology_Notes, Time_of_Introduction, Weakness_Ordinalities
2010-06-21	CWE Content Team	MITRE
2010-06-21	updated Common_Consequences, Demonstrative_Examples, Description, Detection_Factors, Potential_Mitigations, References, Relationships
2010-09-27	CWE Content Team	MITRE
2010-09-27	updated Potential_Mitigations
2010-12-13	CWE Content Team	MITRE
2010-12-13	updated Potential_Mitigations
2011-03-29	CWE Content Team	MITRE
2011-03-29	updated Potential_Mitigations
2011-06-27	CWE Content Team	MITRE
2011-06-27	updated Relationships
2011-09-13	CWE Content Team	MITRE
2011-09-13	updated Potential_Mitigations, References, Relationships, Taxonomy_Mappings
2012-05-11	CWE Content Team	MITRE
2012-05-11	updated Demonstrative_Examples, References, Relationships
2012-10-30	CWE Content Team	MITRE
2012-10-30	updated Potential_Mitigations
2013-02-21	CWE Content Team	MITRE
2013-02-21	updated Observed_Examples
2013-07-17	CWE Content Team	MITRE
2013-07-17	updated Related_Attack_Patterns, Relationships
2014-06-23	CWE Content Team	MITRE
2014-06-23	updated Other_Notes, Research_Gaps
2014-07-30	CWE Content Team	MITRE
2014-07-30	updated Detection_Factors, Relationships, Taxonomy_Mappings
2015-12-07	CWE Content Team	MITRE
2015-12-07	updated Relationships
2017-01-19	CWE Content Team	MITRE
2017-01-19	updated Related_Attack_Patterns
2017-05-03	CWE Content Team	MITRE
2017-05-03	updated Demonstrative_Examples
2017-11-08	CWE Content Team	MITRE
2017-11-08	updated Affected_Resources, Causal_Nature, Likelihood_of_Exploit, References, Relationships, Relevant_Properties, Taxonomy_Mappings
2018-03-27	CWE Content Team	MITRE
2018-03-27	updated References, Relationships
2019-01-03	CWE Content Team	MITRE
2019-01-03	updated References, Related_Attack_Patterns, Relationships, Taxonomy_Mappings
2019-06-20	CWE Content Team	MITRE
2019-06-20	updated Related_Attack_Patterns, Relationships, Type
2019-09-19	CWE Content Team	MITRE
2019-09-19	updated Relationships
2020-02-24	CWE Content Team	MITRE
2020-02-24	updated Potential_Mitigations, Relationships
2020-06-25	CWE Content Team	MITRE
2020-06-25	updated Demonstrative_Examples, Potential_Mitigations
2020-08-20	CWE Content Team	MITRE
2020-08-20	updated Relationships
2020-12-10	CWE Content Team	MITRE
2020-12-10	updated Potential_Mitigations, Relationships
2021-03-15	CWE Content Team	MITRE
2021-03-15	updated Demonstrative_Examples, Relationships
2021-07-20	CWE Content Team	MITRE
2021-07-20	updated Relationships
2021-10-28	CWE Content Team	MITRE
2021-10-28	updated Observed_Examples, Relationships
2022-06-28	CWE Content Team	MITRE
2022-06-28	updated Observed_Examples, Relationships
2022-10-13	CWE Content Team	MITRE
2022-10-13	updated Observed_Examples, References
2023-01-31	CWE Content Team	MITRE
2023-01-31	updated Common_Consequences, Description, Detection_Factors
2023-04-27	CWE Content Team	MITRE
2023-04-27	updated Demonstrative_Examples, References, Relationships, Time_of_Introduction
2023-06-29	CWE Content Team	MITRE
2023-06-29	updated Mapping_Notes, Relationships
2023-10-26	CWE Content Team	MITRE
2023-10-26	updated Observed_Examples
Previous Entry Names
Change Date	Previous Entry Name
2010-02-16	Path Traversal

Weakness ID: 59

View customized information:

Description

The product attempts to access a file based on the filename, but it does not properly prevent that filename from identifying a link or shortcut that resolves to an unintended resource.

Alternate Terms

insecure temporary file:	Some people use the phrase "insecure temporary file" when referring to a link following weakness, but other weaknesses can produce insecure temporary files without any symlink involvement at all.
Zip Slip:	"Zip slip" is an attack that uses file archives (e.g., ZIP, tar, rar, etc.) that contain filenames with path traversal sequences that cause the files to be written outside of the directory under which the archive is expected to be extracted [REF-1282]. It is most commonly used for relative path traversal (CWE-23) and link following (CWE-59).

Relationships

Relevant to the view "Research Concepts" (CWE-1000)

Nature	Type	ID	Name
ChildOf	Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource.	706	Use of Incorrectly-Resolved Name or Reference
ParentOf	Composite - a Compound Element that consists of two or more distinct weaknesses, in which all weaknesses must be present at the same time in order for a potential vulnerability to arise. Removing any of the weaknesses eliminates or sharply reduces the risk. One weakness, X, can be "broken down" into component weaknesses Y and Z. There can be cases in which one weakness might not be essential to a composite, but changes the nature of the composite when it becomes a vulnerability.	61	UNIX Symbolic Link (Symlink) Following
ParentOf	Variant - a weakness that is linked to a certain type of product, typically involving a specific language or technology. More specific than a Base weakness. Variant level weaknesses typically describe issues in terms of 3 to 5 of the following dimensions: behavior, property, technology, language, and resource.	62	UNIX Hard Link
ParentOf	Variant - a weakness that is linked to a certain type of product, typically involving a specific language or technology. More specific than a Base weakness. Variant level weaknesses typically describe issues in terms of 3 to 5 of the following dimensions: behavior, property, technology, language, and resource.	64	Windows Shortcut Following (.LNK)
ParentOf	Variant - a weakness that is linked to a certain type of product, typically involving a specific language or technology. More specific than a Base weakness. Variant level weaknesses typically describe issues in terms of 3 to 5 of the following dimensions: behavior, property, technology, language, and resource.	65	Windows Hard Link
ParentOf	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	1386	Insecure Operation on Windows Junction / Mount Point
CanFollow	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	73	External Control of File Name or Path
CanFollow	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	363	Race Condition Enabling Link Following

Relevant to the view "Software Development" (CWE-699)

Nature	Type	ID	Name
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1219	File Handling Issues

Relevant to the view "Weaknesses for Simplified Mapping of Published Vulnerabilities" (CWE-1003)

Nature	Type	ID	Name
ChildOf	Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource.	706	Use of Incorrectly-Resolved Name or Reference

Relevant to the view "Architectural Concepts" (CWE-1008)

Nature	Type	ID	Name
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1019	Validate Inputs

Background Details

Soft links are a UNIX term that is synonymous with simple shortcuts on Windows-based platforms.

Modes Of Introduction

Phase	Note
Implementation	REALIZATION: This weakness is caused during implementation of an architectural security tactic.

Applicable Platforms

Languages

Class: Not Language-Specific (Undetermined Prevalence)

Operating Systems

Class: Windows (Sometimes Prevalent)

Class: Unix (Often Prevalent)

Common Consequences

Scope	Impact	Likelihood
Confidentiality Integrity Access Control	Technical Impact: Read Files or Directories; Modify Files or Directories; Bypass Protection Mechanism An attacker may be able to traverse the file system to unintended locations and read or overwrite the contents of unexpected files. If the files are used for a security mechanism then an attacker may be able to bypass the mechanism.
Other	Technical Impact: Execute Unauthorized Code or Commands Windows simple shortcuts, sometimes referred to as soft links, can be exploited remotely since a ".LNK" file can be uploaded like a normal file. This can enable remote execution.

Likelihood Of Exploit

Medium

Observed Examples

Reference	Description
CVE-1999-1386	Some versions of Perl follow symbolic links when running with the -e option, which allows local users to overwrite arbitrary files via a symlink attack.
CVE-2000-1178	Text editor follows symbolic links when creating a rescue copy during an abnormal exit, which allows local users to overwrite the files of other users.
CVE-2004-0217	Antivirus update allows local users to create or append to arbitrary files via a symlink attack on a logfile.
CVE-2003-0517	Symlink attack allows local users to overwrite files.
CVE-2004-0689	Window manager does not properly handle when certain symbolic links point to "stale" locations, which could allow local users to create or truncate arbitrary files.
CVE-2005-1879	Second-order symlink vulnerabilities
CVE-2005-1880	Second-order symlink vulnerabilities
CVE-2005-1916	Symlink in Python program
CVE-2000-0972	Setuid product allows file reading by replacing a file being edited with a symlink to the targeted file, leaking the result in error messages when parsing fails.
CVE-2005-0824	Signal causes a dump that follows symlinks.
CVE-2001-1494	Hard link attack, file overwrite; interesting because program checks against soft links
CVE-2002-0793	Hard link and possibly symbolic link following vulnerabilities in embedded operating system allow local users to overwrite arbitrary files.
CVE-2003-0578	Server creates hard links and unlinks files as root, which allows local users to gain privileges by deleting and overwriting arbitrary files.
CVE-1999-0783	Operating system allows local users to conduct a denial of service by creating a hard link from a device special file to a file on an NFS file system.
CVE-2004-1603	Web hosting manager follows hard links, which allows local users to read or modify arbitrary files.
CVE-2004-1901	Package listing system allows local users to overwrite arbitrary files via a hard link attack on the lockfiles.
CVE-2005-1111	Hard link race condition
CVE-2000-0342	Mail client allows remote attackers to bypass the user warning for executable attachments such as .exe, .com, and .bat by using a .lnk file that refers to the attachment, aka "Stealth Attachment."
CVE-2001-1042	FTP server allows remote attackers to read arbitrary files and directories by uploading a .lnk (link) file that points to the target file.
CVE-2001-1043	FTP server allows remote attackers to read arbitrary files and directories by uploading a .lnk (link) file that points to the target file.
CVE-2005-0587	Browser allows remote malicious web sites to overwrite arbitrary files by tricking the user into downloading a .LNK (link) file twice, which overwrites the file that was referenced in the first .LNK file.
CVE-2001-1386	".LNK." - .LNK with trailing dot
CVE-2003-1233	Rootkits can bypass file access restrictions to Windows kernel directories using NtCreateSymbolicLinkObject function to create symbolic link
CVE-2002-0725	File system allows local attackers to hide file usage activities via a hard link to the target file, which causes the link to be recorded in the audit trail instead of the target file.
CVE-2003-0844	Web server plugin allows local users to overwrite arbitrary files via a symlink attack on predictable temporary filenames.
CVE-2015-3629	A Libcontainer used in Docker Engine allows local users to escape containerization and write to an arbitrary file on the host system via a symlink attack in an image when respawning a container.
CVE-2021-21272	"Zip Slip" vulnerability in Go-based Open Container Initiative (OCI) registries product allows writing arbitrary files outside intended directory via symbolic links or hard links in a gzipped tarball.
CVE-2020-27833	"Zip Slip" vulnerability in container management product allows writing arbitrary files outside intended directory via a container image (.tar format) with filenames that are symbolic links that point to other files within the same tar file; however, the files being pointed to can also be symbolic links to destinations outside the intended directory, bypassing the initial check.

Potential Mitigations

Phase: Architecture and Design

Strategy: Separation of Privilege

Follow the principle of least privilege when assigning access rights to entities in a software system.

Denying access to a file can prevent an attacker from replacing that file with a link to a sensitive file. Ensure good compartmentalization in the system to provide protected areas that can be trusted.

Weakness Ordinalities

Ordinality	Description
Resultant	(where the weakness is typically related to the presence of some other weaknesses)

Detection Methods

Automated Static Analysis - Binary or Bytecode

According to SOAR, the following detection techniques may be useful:

Cost effective for partial coverage:

Bytecode Weakness Analysis - including disassembler + source code weakness analysis

Effectiveness: SOAR Partial

Manual Static Analysis - Binary or Bytecode

According to SOAR, the following detection techniques may be useful:

Cost effective for partial coverage:

Binary / Bytecode disassembler - then use manual analysis for vulnerabilities & anomalies

Effectiveness: SOAR Partial

Dynamic Analysis with Automated Results Interpretation

According to SOAR, the following detection techniques may be useful:

Cost effective for partial coverage:

Web Application Scanner

Web Services Scanner

Database Scanners

Effectiveness: SOAR Partial

Dynamic Analysis with Manual Results Interpretation

According to SOAR, the following detection techniques may be useful:

Cost effective for partial coverage:

Fuzz Tester

Framework-based Fuzzer

Effectiveness: SOAR Partial

Manual Static Analysis - Source Code

According to SOAR, the following detection techniques may be useful:

Highly cost effective:

Focused Manual Spotcheck - Focused manual analysis of source

Manual Source Code Review (not inspections)

Effectiveness: High

Automated Static Analysis - Source Code

According to SOAR, the following detection techniques may be useful:

Cost effective for partial coverage:

Source code Weakness Analyzer

Context-configured Source Code Weakness Analyzer

Effectiveness: SOAR Partial

Architecture or Design Review

According to SOAR, the following detection techniques may be useful:

Highly cost effective:

Formal Methods / Correct-By-Construction

Cost effective for partial coverage:

Inspection (IEEE 1028 standard) (can apply to requirements, design, source code, etc.)

Effectiveness: High

Functional Areas

File Processing

Affected Resources

File or Directory

Memberships

Nature	Type	ID	Name
MemberOf	View - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries).	635	Weaknesses Originally Used by NVD from 2008 to 2016
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	743	CERT C Secure Coding Standard (2008) Chapter 10 - Input Output (FIO)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	748	CERT C Secure Coding Standard (2008) Appendix - POSIX (POS)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	808	2010 Top 25 - Weaknesses On the Cusp
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	877	CERT C++ Secure Coding Section 09 - Input Output (FIO)
MemberOf	View - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries).	884	CWE Cross-section
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	980	SFP Secondary Cluster: Link in Resource Name Resolution
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1185	SEI CERT Perl Coding Standard - Guidelines 07. File Input and Output (FIO)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1345	OWASP Top Ten 2021 Category A01:2021 - Broken Access Control
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1404	Comprehensive Categorization: File Handling

Vulnerability Mapping Notes

Usage: ALLOWED

(this CWE ID could be used to map to real-world vulnerabilities)

Reason: Acceptable-Use

Rationale:

This CWE entry is at the Base level of abstraction, which is a preferred level of abstraction for mapping to the root causes of vulnerabilities.

Comments:

Notes

Theoretical

Link following vulnerabilities are Multi-factor Vulnerabilities (MFV). They are the combination of multiple elements: file or directory permissions, filename predictability, race conditions, and in some cases, a design limitation in which there is no mechanism for performing atomic file creation operations.

Some potential factors are race conditions, permissions, and predictability.

Taxonomy Mappings

Mapped Taxonomy Name	Node ID	Fit	Mapped Node Name
PLOVER			Link Following
CERT C Secure Coding	FIO02-C		Canonicalize path names originating from untrusted sources
CERT C Secure Coding	POS01-C		Check for the existence of links when dealing with files
SEI CERT Perl Coding Standard	FIO01-PL	CWE More Specific	Do not operate on files that can be modified by untrusted users
Software Fault Patterns	SFP18		Link in resource name resolution

Related Attack Patterns

CAPEC-ID	Attack Pattern Name
CAPEC-132	Symlink Attack
CAPEC-17	Using Malicious Files
CAPEC-35	Leverage Executable Code in Non-Executable Files
CAPEC-76	Manipulating Web Input to File System Calls

References

[REF-62] Mark Dowd, John McDonald and Justin Schuh. "The Art of Software Security Assessment". Chapter 9, "Symbolic Link Attacks", Page 518. 1st Edition. Addison Wesley. 2006.

[REF-1282] Snyk. "Zip Slip Vulnerability". 2018-06-05. <https://security.snyk.io/research/zip-slip-vulnerability>.

Content History

Submissions
Submission Date	Submitter	Organization
2006-07-19 (CWE Draft 3, 2006-07-19)	PLOVER
2006-07-19 (CWE Draft 3, 2006-07-19)
Modifications
Modification Date	Modifier	Organization
2008-07-01	Eric Dalci	Cigital
2008-07-01	updated Time_of_Introduction
2008-09-08	CWE Content Team	MITRE
2008-09-08	updated Alternate_Terms, Applicable_Platforms, Relationships, Other_Notes, Relationship_Notes, Taxonomy_Mappings, Weakness_Ordinalities
2008-11-24	CWE Content Team	MITRE
2008-11-24	updated Relationships, Taxonomy_Mappings
2009-01-12	CWE Content Team	MITRE
2009-01-12	updated Relationships
2009-05-27	CWE Content Team	MITRE
2009-05-27	updated Description, Name
2009-10-29	CWE Content Team	MITRE
2009-10-29	updated Background_Details, Other_Notes
2010-02-16	CWE Content Team	MITRE
2010-02-16	updated Potential_Mitigations, Relationships
2010-04-05	CWE Content Team	MITRE
2010-04-05	updated Related_Attack_Patterns
2011-06-01	CWE Content Team	MITRE
2011-06-01	updated Common_Consequences
2011-09-13	CWE Content Team	MITRE
2011-09-13	updated Relationships, Taxonomy_Mappings
2012-05-11	CWE Content Team	MITRE
2012-05-11	updated Common_Consequences, Observed_Examples, References, Relationships
2012-10-30	CWE Content Team	MITRE
2012-10-30	updated Potential_Mitigations
2014-06-23	CWE Content Team	MITRE
2014-06-23	updated Common_Consequences, Other_Notes
2014-07-30	CWE Content Team	MITRE
2014-07-30	updated Detection_Factors, Relationships, Taxonomy_Mappings
2015-12-07	CWE Content Team	MITRE
2015-12-07	updated Relationships
2017-11-08	CWE Content Team	MITRE
2017-11-08	updated Affected_Resources, Applicable_Platforms, Causal_Nature, Common_Consequences, Functional_Areas, Likelihood_of_Exploit, Modes_of_Introduction, Relationships, Taxonomy_Mappings
2019-01-03	CWE Content Team	MITRE
2019-01-03	updated Taxonomy_Mappings
2019-06-20	CWE Content Team	MITRE
2019-06-20	updated Relationships
2020-02-24	CWE Content Team	MITRE
2020-02-24	updated Relationships
2021-03-15	CWE Content Team	MITRE
2021-03-15	updated Relationships
2021-10-28	CWE Content Team	MITRE
2021-10-28	updated Relationships
2022-04-28	CWE Content Team	MITRE
2022-04-28	updated Research_Gaps
2022-06-28	CWE Content Team	MITRE
2022-06-28	updated Relationships
2022-10-13	CWE Content Team	MITRE
2022-10-13	updated Alternate_Terms, Background_Details, Observed_Examples, References, Relationship_Notes, Theoretical_Notes
2023-01-31	CWE Content Team	MITRE
2023-01-31	updated Description
2023-04-27	CWE Content Team	MITRE
2023-04-27	updated Relationships
2023-06-29	CWE Content Team	MITRE
2023-06-29	updated Mapping_Notes
Previous Entry Names
Change Date	Previous Entry Name
2008-04-11	Link Following

2009-05-27	Failure to Resolve Links Before File Access (aka 'Link Following')

Weakness ID: 95

Vulnerability Mapping: ALLOWEDThis CWE ID may be used to map to real-world vulnerabilities
Abstraction: VariantVariant - a weakness that is linked to a certain type of product, typically involving a specific language or technology. More specific than a Base weakness. Variant level weaknesses typically describe issues in terms of 3 to 5 of the following dimensions: behavior, property, technology, language, and resource.

View customized information:

Description

The product receives input from an upstream component, but it does not neutralize or incorrectly neutralizes code syntax before using the input in a dynamic evaluation call (e.g. "eval").

Extended Description

This may allow an attacker to execute arbitrary code, or at least modify what code can be executed.

Relationships

Relevant to the view "Research Concepts" (CWE-1000)

Nature	Type	ID	Name
ChildOf	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	94	Improper Control of Generation of Code ('Code Injection')

Relevant to the view "Architectural Concepts" (CWE-1008)

Nature	Type	ID	Name
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1019	Validate Inputs

Modes Of Introduction

Phase	Note
Implementation	REALIZATION: This weakness is caused during implementation of an architectural security tactic.
Implementation	This weakness is prevalent in handler/dispatch procedures that might want to invoke a large number of functions, or set a large number of variables.

Applicable Platforms

Languages

Java (Undetermined Prevalence)

JavaScript (Undetermined Prevalence)

Python (Undetermined Prevalence)

Perl (Undetermined Prevalence)

PHP (Undetermined Prevalence)

Ruby (Undetermined Prevalence)

Class: Interpreted (Undetermined Prevalence)

Common Consequences

Scope	Impact	Likelihood
Confidentiality	Technical Impact: Read Files or Directories; Read Application Data The injected code could access restricted data / files.
Access Control	Technical Impact: Bypass Protection Mechanism In some cases, injectable code controls authentication; this may lead to a remote vulnerability.
Access Control	Technical Impact: Gain Privileges or Assume Identity Injected code can access resources that the attacker is directly prevented from accessing.
Integrity Confidentiality Availability Other	Technical Impact: Execute Unauthorized Code or Commands Code injection attacks can lead to loss of data integrity in nearly all cases as the control-plane data injected is always incidental to data recall or writing. Additionally, code injection can often result in the execution of arbitrary code.
Non-Repudiation	Technical Impact: Hide Activities Often the actions performed by injected control code are unlogged.

Likelihood Of Exploit

Medium

Demonstrative Examples

Example 1

edit-config.pl: This CGI script is used to modify settings in a configuration file.

(bad code)

Example Language: Perl

use CGI qw(:standard);

sub config_file_add_key {

my ($fname, $key, $arg) = @_;
# code to add a field/key to a file goes here

}

sub config_file_set_key {

my ($fname, $key, $arg) = @_;
# code to set key to a particular file goes here

}

sub config_file_delete_key {

my ($fname, $key, $arg) = @_;
# code to delete key from a particular file goes here

}

sub handleConfigAction {

my ($fname, $action) = @_;
my $key = param('key');
my $val = param('val');
# this is super-efficient code, especially if you have to invoke
# any one of dozens of different functions!

my $code = "config_file_$action_key(\$fname, \$key, \$val);";
eval($code);

}

$configfile = "/home/cwe/config.txt";
print header;
if (defined(param('action'))) {

handleConfigAction($configfile, param('action'));

}
else {

print "No action specified!\n";

}

The script intends to take the 'action' parameter and invoke one of a variety of functions based on the value of that parameter - config_file_add_key(), config_file_set_key(), or config_file_delete_key(). It could set up a conditional to invoke each function separately, but eval() is a powerful way of doing the same thing in fewer lines of code, especially when a large number of functions or variables are involved. Unfortunately, in this case, the attacker can provide other values in the action parameter, such as:

(attack code)

add_key(",","); system("/bin/ls");

This would produce the following string in handleConfigAction():

(result)

config_file_add_key(",","); system("/bin/ls");

Any arbitrary Perl code could be added after the attacker has "closed off" the construction of the original function call, in order to prevent parsing errors from causing the malicious eval() to fail before the attacker's payload is activated. This particular manipulation would fail after the system() call, because the "_key(\$fname, \$key, \$val)" portion of the string would cause an error, but this is irrelevant to the attack because the payload has already been activated.

Example 2

This simple script asks a user to supply a list of numbers as input and adds them together.

(bad code)

Example Language: Python

def main():

sum = 0
numbers = eval(input("Enter a space-separated list of numbers: "))
for num in numbers:

sum = sum + num

print(f"Sum of {numbers} = {sum}")

main()

The eval() function can take the user-supplied list and convert it into a Python list object, therefore allowing the programmer to use list comprehension methods to work with the data. However, if code is supplied to the eval() function, it will execute that code. For example, a malicious user could supply the following string:

(attack code)

__import__('subprocess').getoutput('rm -r *')

This would delete all the files in the current directory. For this reason, it is not recommended to use eval() with untrusted input.

A way to accomplish this without the use of eval() is to apply an integer conversion on the input within a try/except block. If the user-supplied input is not numeric, this will raise a ValueError. By avoiding eval(), there is no opportunity for the input string to be executed as code.

(good code)

Example Language: Python

def main():

sum = 0
numbers = input("Enter a space-separated list of numbers: ").split(" ")
try:

for num in numbers:

sum = sum + int(num)

print(f"Sum of {numbers} = {sum}")

except ValueError:

print("Error: invalid input")

main()

An alternative, commonly-cited mitigation for this kind of weakness is to use the ast.literal_eval() function, since it is intentionally designed to avoid executing code. However, an adversary could still cause excessive memory or stack consumption via deeply nested structures [REF-1372], so the python documentation discourages use of ast.literal_eval() on untrusted data [REF-1373].

Observed Examples

Reference	Description
CVE-2022-2054	Python compiler uses eval() to execute malicious strings as Python code.
CVE-2021-22204	Chain: regex in EXIF processor code does not correctly determine where a string ends (CWE-625), enabling eval injection (CWE-95), as exploited in the wild per CISA KEV.
CVE-2021-22205	Chain: backslash followed by a newline can bypass a validation step (CWE-20), leading to eval injection (CWE-95), as exploited in the wild per CISA KEV.
CVE-2008-5071	Eval injection in PHP program.
CVE-2002-1750	Eval injection in Perl program.
CVE-2008-5305	Eval injection in Perl program using an ID that should only contain hyphens and numbers.
CVE-2002-1752	Direct code injection into Perl eval function.
CVE-2002-1753	Eval injection in Perl program.
CVE-2005-1527	Direct code injection into Perl eval function.
CVE-2005-2837	Direct code injection into Perl eval function.
CVE-2005-1921	MFV. code injection into PHP eval statement using nested constructs that should not be nested.
CVE-2005-2498	MFV. code injection into PHP eval statement using nested constructs that should not be nested.
CVE-2005-3302	Code injection into Python eval statement from a field in a formatted file.
CVE-2007-1253	Eval injection in Python program.
CVE-2001-1471	chain: Resultant eval injection. An invalid value prevents initialization of variables, which can be modified by attacker and later injected into PHP eval statement.
CVE-2007-2713	Chain: Execution after redirect triggers eval injection.

Potential Mitigations

Phases: Architecture and Design; Implementation

If possible, refactor your code so that it does not need to use eval() at all.

Phase: Implementation

Strategy: Input Validation

Phase: Implementation

Inputs should be decoded and canonicalized to the application's current internal representation before being validated (CWE-180, CWE-181). Make sure that your application does not inadvertently decode the same input twice (CWE-174). Such errors could be used to bypass allowlist schemes by introducing dangerous inputs after they have been checked. Use libraries such as the OWASP ESAPI Canonicalization control.

Consider performing repeated canonicalization until your input does not change any more. This will avoid double-decoding and similar scenarios, but it might inadvertently modify inputs that are allowed to contain properly-encoded dangerous content.

Phase: Implementation

For Python programs, it is frequently encouraged to use the ast.literal_eval() function instead of eval, since it is intentionally designed to avoid executing code. However, an adversary could still cause excessive memory or stack consumption via deeply nested structures [REF-1372], so the python documentation discourages use of ast.literal_eval() on untrusted data [REF-1373].

Effectiveness: Discouraged Common Practice

Weakness Ordinalities

Ordinality	Description
Primary	(where the weakness exists independent of other weaknesses)

Detection Methods

Automated Static Analysis

Effectiveness: High

Memberships

Nature	Type	ID	Name
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	714	OWASP Top Ten 2007 Category A3 - Malicious File Execution
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	727	OWASP Top Ten 2004 Category A6 - Injection Flaws
MemberOf	View - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries).	884	CWE Cross-section
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	990	SFP Secondary Cluster: Tainted Input to Command
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1179	SEI CERT Perl Coding Standard - Guidelines 01. Input Validation and Data Sanitization (IDS)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1347	OWASP Top Ten 2021 Category A03:2021 - Injection
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1409	Comprehensive Categorization: Injection

Vulnerability Mapping Notes

Usage: ALLOWED

(this CWE ID could be used to map to real-world vulnerabilities)

Reason: Acceptable-Use

Rationale:

This CWE entry is at the Variant level of abstraction, which is a preferred level of abstraction for mapping to the root causes of vulnerabilities.

Comments:

Notes

Other

Factors: special character errors can play a role in increasing the variety of code that can be injected, although some vulnerabilities do not require special characters at all, e.g. when a single function without arguments can be referenced and a terminator character is not necessary.

Taxonomy Mappings

Mapped Taxonomy Name	Node ID	Fit	Mapped Node Name
PLOVER			Direct Dynamic Code Evaluation ('Eval Injection')
OWASP Top Ten 2007	A3	CWE More Specific	Malicious File Execution
OWASP Top Ten 2004	A6	CWE More Specific	Injection Flaws
Software Fault Patterns	SFP24		Tainted input to command
SEI CERT Perl Coding Standard	IDS35-PL	Exact	Do not invoke the eval form with a string argument

Related Attack Patterns

CAPEC-ID	Attack Pattern Name
CAPEC-35	Leverage Executable Code in Non-Executable Files

References

[REF-62] Mark Dowd, John McDonald and Justin Schuh. "The Art of Software Security Assessment". Chapter 18, "Inline Evaluation", Page 1095. 1st Edition. Addison Wesley. 2006.

[REF-1372] "How ast.literal_eval can cause memory exhaustion". Reddit. 2022-12-14. <https://www.reddit.com/r/learnpython/comments/zmbhcf/how_astliteral_eval_can_cause_memory_exhaustion/>. URL validated: 2023-11-03.

[REF-1373] "ast - Abstract Syntax Trees". ast.literal_eval(node_or_string). Python. 2023-11-02. <https://docs.python.org/3/library/ast.html#ast.literal_eval>. URL validated: 2023-11-03.

Content History

Submissions
Submission Date	Submitter	Organization
2006-07-19 (CWE Draft 3, 2006-07-19)	PLOVER
2006-07-19 (CWE Draft 3, 2006-07-19)
Modifications
Modification Date	Modifier	Organization
2008-07-01	Eric Dalci	Cigital
2008-07-01	updated Time_of_Introduction
2008-08-15		Veracode
2008-08-15	Suggested OWASP Top Ten 2004 mapping
2008-09-08	CWE Content Team	MITRE
2008-09-08	updated Applicable_Platforms, Description, Modes_of_Introduction, Relationships, Other_Notes, Taxonomy_Mappings, Weakness_Ordinalities
2009-01-12	CWE Content Team	MITRE
2009-01-12	updated Description, Observed_Examples, Other_Notes, Research_Gaps
2009-05-27	CWE Content Team	MITRE
2009-05-27	updated Alternate_Terms, Applicable_Platforms, Demonstrative_Examples, Description, Name, References
2010-02-16	CWE Content Team	MITRE
2010-02-16	updated Potential_Mitigations
2010-06-21	CWE Content Team	MITRE
2010-06-21	updated Description, Name
2011-06-01	CWE Content Team	MITRE
2011-06-01	updated Common_Consequences
2012-05-11	CWE Content Team	MITRE
2012-05-11	updated Common_Consequences, Demonstrative_Examples, References, Relationships
2012-10-30	CWE Content Team	MITRE
2012-10-30	updated Potential_Mitigations
2013-02-21	CWE Content Team	MITRE
2013-02-21	updated Observed_Examples
2014-07-30	CWE Content Team	MITRE
2014-07-30	updated Relationships, Taxonomy_Mappings
2017-11-08	CWE Content Team	MITRE
2017-11-08	updated Causal_Nature, Modes_of_Introduction, References, Relationships, Taxonomy_Mappings
2019-01-03	CWE Content Team	MITRE
2019-01-03	updated Taxonomy_Mappings
2019-06-20	CWE Content Team	MITRE
2019-06-20	updated Type
2020-02-24	CWE Content Team	MITRE
2020-02-24	updated Potential_Mitigations, Relationships
2020-06-25	CWE Content Team	MITRE
2020-06-25	updated Potential_Mitigations
2021-03-15	CWE Content Team	MITRE
2021-03-15	updated Relationships
2021-10-28	CWE Content Team	MITRE
2021-10-28	updated Relationships
2022-04-28	CWE Content Team	MITRE
2022-04-28	updated Research_Gaps
2022-06-28	CWE Content Team	MITRE
2022-06-28	updated Observed_Examples
2022-10-13	CWE Content Team	MITRE
2022-10-13	updated Observed_Examples
2023-01-31	CWE Content Team	MITRE
2023-01-31	updated Demonstrative_Examples, Description
2023-04-27	CWE Content Team	MITRE
2023-04-27	updated Demonstrative_Examples, Detection_Factors, Relationships, Time_of_Introduction
2023-06-29	CWE Content Team	MITRE
2023-06-29	updated Mapping_Notes
2024-02-29 (CWE 4.14, 2024-02-29)	CWE Content Team	MITRE
2024-02-29 (CWE 4.14, 2024-02-29)	updated Demonstrative_Examples, Potential_Mitigations, References
Previous Entry Names
Change Date	Previous Entry Name
2008-04-11	Direct Dynamic Code Evaluation ('Eval Injection')

2009-05-27	Insufficient Control of Directives in Dynamically Evaluated Code (aka 'Eval Injection')

2010-06-21	Improper Sanitization of Directives in Dynamically Evaluated Code ('Eval Injection')

Weakness ID: 77

View customized information:

Description

Extended Description

Command injection vulnerabilities typically occur when:

1. Data enters the application from an untrusted source.

2. The data is part of a string that is executed as a command by the application.

3. By executing the command, the application gives an attacker a privilege or capability that the attacker would not otherwise have.

Many protocols and products have their own custom command language. While OS or shell command strings are frequently discovered and targeted, developers may not realize that these other command languages might also be vulnerable to attacks.

Command injection is a common problem with wrapper programs.

Relationships

Relevant to the view "Research Concepts" (CWE-1000)

Nature	Type	ID	Name
ChildOf	Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource.	74	Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')
ParentOf	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	78	Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')
ParentOf	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	88	Improper Neutralization of Argument Delimiters in a Command ('Argument Injection')
ParentOf	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	624	Executable Regular Expression Error
ParentOf	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	917	Improper Neutralization of Special Elements used in an Expression Language Statement ('Expression Language Injection')

Relevant to the view "Weaknesses for Simplified Mapping of Published Vulnerabilities" (CWE-1003)

Nature	Type	ID	Name
ChildOf	Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource.	74	Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')

Relevant to the view "Architectural Concepts" (CWE-1008)

Nature	Type	ID	Name
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1019	Validate Inputs

Relevant to the view "CISQ Quality Measures (2020)" (CWE-1305)

Nature	Type	ID	Name
ParentOf	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	78	Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')
ParentOf	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	88	Improper Neutralization of Argument Delimiters in a Command ('Argument Injection')
ParentOf	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	624	Executable Regular Expression Error
ParentOf	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	917	Improper Neutralization of Special Elements used in an Expression Language Statement ('Expression Language Injection')

Relevant to the view "CISQ Data Protection Measures" (CWE-1340)

Nature	Type	ID	Name
ParentOf	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	78	Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')
ParentOf	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	88	Improper Neutralization of Argument Delimiters in a Command ('Argument Injection')
ParentOf	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	624	Executable Regular Expression Error
ParentOf	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	917	Improper Neutralization of Special Elements used in an Expression Language Statement ('Expression Language Injection')

Modes Of Introduction

Phase	Note
Implementation	REALIZATION: This weakness is caused during implementation of an architectural security tactic.

Applicable Platforms

Languages

Class: Not Language-Specific (Undetermined Prevalence)

Common Consequences

Scope	Impact	Likelihood
Integrity Confidentiality Availability	Technical Impact: Execute Unauthorized Code or Commands If a malicious user injects a character (such as a semi-colon) that delimits the end of one command and the beginning of another, it may be possible to then insert an entirely new and unrelated command that was not intended to be executed.

Likelihood Of Exploit

High

Demonstrative Examples

Example 1

The following simple program accepts a filename as a command line argument and displays the contents of the file back to the user. The program is installed setuid root because it is intended for use as a learning tool to allow system administrators in-training to inspect privileged system files without giving them the ability to modify them or damage the system.

(bad code)

Example Language: C

int main(int argc, char** argv) {

char cmd[CMD_MAX] = "/usr/bin/cat ";
strcat(cmd, argv[1]);
system(cmd);

}

Because the program runs with root privileges, the call to system() also executes with root privileges. If a user specifies a standard filename, the call works as expected. However, if an attacker passes a string of the form ";rm -rf /", then the call to system() fails to execute cat due to a lack of arguments and then plows on to recursively delete the contents of the root partition.

Note that if argv[1] is a very long argument, then this issue might also be subject to a buffer overflow (CWE-120).

Example 2

The following code is from an administrative web application designed to allow users to kick off a backup of an Oracle database using a batch-file wrapper around the rman utility and then run a cleanup.bat script to delete some temporary files. The script rmanDB.bat accepts a single command line parameter, which specifies what type of backup to perform. Because access to the database is restricted, the application runs the backup as a privileged user.

(bad code)

Example Language: Java

...
String btype = request.getParameter("backuptype");
String cmd = new String("cmd.exe /K \"

c:\\util\\rmanDB.bat "
+btype+
"&&c:\\utl\\cleanup.bat\"")

System.Runtime.getRuntime().exec(cmd);
...

The problem here is that the program does not do any validation on the backuptype parameter read from the user. Typically the Runtime.exec() function will not execute multiple commands, but in this case the program first runs the cmd.exe shell in order to run multiple commands with a single call to Runtime.exec(). Once the shell is invoked, it will happily execute multiple commands separated by two ampersands. If an attacker passes a string of the form "& del c:\\dbms\\*.*", then the application will execute this command along with the others specified by the program. Because of the nature of the application, it runs with the privileges necessary to interact with the database, which means whatever command the attacker injects will run with those privileges as well.

Example 3

The following code from a system utility uses the system property APPHOME to determine the directory in which it is installed and then executes an initialization script based on a relative path from the specified directory.

(bad code)

Example Language: Java

...
String home = System.getProperty("APPHOME");
String cmd = home + INITCMD;
java.lang.Runtime.getRuntime().exec(cmd);
...

The code above allows an attacker to execute arbitrary commands with the elevated privilege of the application by modifying the system property APPHOME to point to a different path containing a malicious version of INITCMD. Because the program does not validate the value read from the environment, if an attacker can control the value of the system property APPHOME, then they can fool the application into running malicious code and take control of the system.

Example 4

The following code is a wrapper around the UNIX command cat which prints the contents of a file to standard out. It is also injectable:

(bad code)

Example Language: C

#include <stdio.h>
#include <unistd.h>

int main(int argc, char **argv) {

char cat[] = "cat ";
char *command;
size_t commandLength;

commandLength = strlen(cat) + strlen(argv[1]) + 1;
command = (char *) malloc(commandLength);
strncpy(command, cat, commandLength);
strncat(command, argv[1], (commandLength - strlen(cat)) );

system(command);
return (0);

}

Used normally, the output is simply the contents of the file requested:

(informative)

$ ./catWrapper Story.txt
When last we left our heroes...

However, if we add a semicolon and another command to the end of this line, the command is executed by catWrapper with no complaint:

(attack code)

$ ./catWrapper Story.txt; ls
When last we left our heroes...
Story.txt
SensitiveFile.txt
PrivateData.db
a.out*

If catWrapper had been set to have a higher privilege level than the standard user, arbitrary commands could be executed with that higher privilege.

Observed Examples

Reference	Description
CVE-2022-36069	Python-based dependency management tool avoids OS command injection when generating Git commands but allows injection of optional arguments with input beginning with a dash, potentially allowing for code execution.
CVE-1999-0067	Canonical example of OS command injection. CGI program does not neutralize "\|" metacharacter when invoking a phonebook program.
CVE-2020-9054	Chain: improper input validation (CWE-20) in username parameter, leading to OS command injection (CWE-78), as exploited in the wild per CISA KEV.
CVE-2022-1509	injection of sed script syntax ("sed injection")
CVE-2021-41282	injection of sed script syntax ("sed injection")
CVE-2019-13398	injection of sed script syntax ("sed injection")
CVE-2019-12921	image program allows injection of commands in "Magick Vector Graphics (MVG)" language.
CVE-2020-11698	anti-spam product allows injection of SNMP commands into confiuration file

Potential Mitigations

Phase: Architecture and Design

If at all possible, use library calls rather than external processes to recreate the desired functionality.

Phase: Implementation

If possible, ensure that all external commands called from the program are statically created.

Phase: Implementation

Strategy: Input Validation

Phase: Operation

Run time: Run time policy enforcement may be used in an allowlist fashion to prevent use of any non-sanctioned commands.

Phase: System Configuration

Assign permissions that prevent the user from accessing/opening privileged files.

Weakness Ordinalities

Ordinality	Description
Primary	(where the weakness exists independent of other weaknesses)

Detection Methods

Automated Static Analysis

Effectiveness: High

Memberships

Nature	Type	ID	Name
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	713	OWASP Top Ten 2007 Category A2 - Injection Flaws
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	722	OWASP Top Ten 2004 Category A1 - Unvalidated Input
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	727	OWASP Top Ten 2004 Category A6 - Injection Flaws
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	929	OWASP Top Ten 2013 Category A1 - Injection
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	990	SFP Secondary Cluster: Tainted Input to Command
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1005	7PK - Input Validation and Representation
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1027	OWASP Top Ten 2017 Category A1 - Injection
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1179	SEI CERT Perl Coding Standard - Guidelines 01. Input Validation and Data Sanitization (IDS)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1308	CISQ Quality Measures - Security
MemberOf	View - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries).	1337	Weaknesses in the 2021 CWE Top 25 Most Dangerous Software Weaknesses
MemberOf	View - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries).	1340	CISQ Data Protection Measures
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1347	OWASP Top Ten 2021 Category A03:2021 - Injection
MemberOf	View - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries).	1387	Weaknesses in the 2022 CWE Top 25 Most Dangerous Software Weaknesses
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1409	Comprehensive Categorization: Injection
MemberOf	View - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries).	1425	Weaknesses in the 2023 CWE Top 25 Most Dangerous Software Weaknesses

Vulnerability Mapping Notes

Usage: ALLOWED-WITH-REVIEW

(this CWE ID could be used to map to real-world vulnerabilities in limited situations requiring careful review)

Reason: Frequent Misuse

Rationale:

CWE-77 is often misused when OS command injection (CWE-78) was intended instead [REF-1287].

Comments:

If the weakness involves a command language besides OS shell invocation, then CWE-77 could be used.

Notes

Terminology

The "command injection" phrase carries different meanings to different people. For some people, it refers to any type of attack that can allow the attacker to execute commands of their own choosing, regardless of how those commands are inserted. The command injection could thus be resultant from another weakness. This usage also includes cases in which the functionality allows the user to specify an entire command, which is then executed; within CWE, this situation might be better regarded as an authorization problem (since an attacker should not be able to specify arbitrary commands.)

Another common usage, which includes CWE-77 and its descendants, involves cases in which the attacker injects separators into the command being constructed.

Taxonomy Mappings

Mapped Taxonomy Name	Node ID	Fit	Mapped Node Name
7 Pernicious Kingdoms			Command Injection
CLASP			Command injection
OWASP Top Ten 2007	A2	CWE More Specific	Injection Flaws
OWASP Top Ten 2004	A1	CWE More Specific	Unvalidated Input
OWASP Top Ten 2004	A6	CWE More Specific	Injection Flaws
Software Fault Patterns	SFP24		Tainted input to command
SEI CERT Perl Coding Standard	IDS34-PL	CWE More Specific	Do not pass untrusted, unsanitized data to a command interpreter

Related Attack Patterns

CAPEC-ID	Attack Pattern Name
CAPEC-136	LDAP Injection
CAPEC-15	Command Delimiters
CAPEC-183	IMAP/SMTP Command Injection
CAPEC-248	Command Injection
CAPEC-40	Manipulating Writeable Terminal Devices
CAPEC-43	Exploiting Multiple Input Interpretation Layers
CAPEC-75	Manipulating Writeable Configuration Files
CAPEC-76	Manipulating Web Input to File System Calls

References

[REF-6] Katrina Tsipenyuk, Brian Chess and Gary McGraw. "Seven Pernicious Kingdoms: A Taxonomy of Software Security Errors". NIST Workshop on Software Security Assurance Tools Techniques and Metrics. NIST. 2005-11-07. <https://samate.nist.gov/SSATTM_Content/papers/Seven%20Pernicious%20Kingdoms%20-%20Taxonomy%20of%20Sw%20Security%20Errors%20-%20Tsipenyuk%20-%20Chess%20-%20McGraw.pdf>.

[REF-140] Greg Hoglund and Gary McGraw. "Exploiting Software: How to Break Code". Addison-Wesley. 2004-02-27. <https://www.amazon.com/Exploiting-Software-How-Break-Code/dp/0201786958>. URL validated: 2023-04-07.

[REF-44] Michael Howard, David LeBlanc and John Viega. "24 Deadly Sins of Software Security". "Sin 10: Command Injection." Page 171. McGraw-Hill. 2010.

[REF-1287] MITRE. "Supplemental Details - 2022 CWE Top 25". Details of Problematic Mappings. 2022-06-28. <https://cwe.mitre.org/top25/archive/2022/2022_cwe_top25_supplemental.html#problematicMappingDetails>.

Content History

Submissions
Submission Date	Submitter	Organization
2006-07-19 (CWE Draft 3, 2006-07-19)	7 Pernicious Kingdoms
2006-07-19 (CWE Draft 3, 2006-07-19)
Contributions
Contribution Date	Contributor	Organization
2022-05-20	Anonymous External Contributor
2022-05-20	reported typo in Terminology note
Modifications
Modification Date	Modifier	Organization
2008-07-01	Eric Dalci	Cigital
2008-07-01	updated Time_of_Introduction
2008-08-15		Veracode
2008-08-15	Suggested OWASP Top Ten 2004 mapping
2008-09-08	CWE Content Team	MITRE
2008-09-08	updated Common_Consequences, Relationships, Other_Notes, Taxonomy_Mappings, Weakness_Ordinalities
2009-05-27	CWE Content Team	MITRE
2009-05-27	updated Demonstrative_Examples, Name
2009-07-27	CWE Content Team	MITRE
2009-07-27	updated Demonstrative_Examples, Description, Name
2009-10-29	CWE Content Team	MITRE
2009-10-29	updated Common_Consequences, Description, Other_Notes, Potential_Mitigations
2010-02-16	CWE Content Team	MITRE
2010-02-16	updated Potential_Mitigations, Relationships
2010-06-21	CWE Content Team	MITRE
2010-06-21	updated Description, Name
2011-03-29	CWE Content Team	MITRE
2011-03-29	updated Demonstrative_Examples
2011-06-01	CWE Content Team	MITRE
2011-06-01	updated Common_Consequences
2012-05-11	CWE Content Team	MITRE
2012-05-11	updated Common_Consequences, Demonstrative_Examples, References, Related_Attack_Patterns, Relationships
2012-10-30	CWE Content Team	MITRE
2012-10-30	updated Potential_Mitigations
2013-02-21	CWE Content Team	MITRE
2013-02-21	updated Relationships
2013-07-17	CWE Content Team	MITRE
2013-07-17	updated Relationships
2014-02-18	CWE Content Team	MITRE
2014-02-18	updated Applicable_Platforms, Demonstrative_Examples, Description, Other_Notes, Terminology_Notes
2014-06-23	CWE Content Team	MITRE
2014-06-23	updated Relationships
2014-07-30	CWE Content Team	MITRE
2014-07-30	updated Relationships, Taxonomy_Mappings
2015-12-07	CWE Content Team	MITRE
2015-12-07	updated Demonstrative_Examples, Relationships
2017-05-03	CWE Content Team	MITRE
2017-05-03	updated Potential_Mitigations, Related_Attack_Patterns, Relationships
2017-11-08	CWE Content Team	MITRE
2017-11-08	updated Causal_Nature, Likelihood_of_Exploit, Modes_of_Introduction, References, Relationships, Taxonomy_Mappings
2018-03-27	CWE Content Team	MITRE
2018-03-27	updated Relationships
2019-01-03	CWE Content Team	MITRE
2019-01-03	updated Taxonomy_Mappings
2019-06-20	CWE Content Team	MITRE
2019-06-20	updated Related_Attack_Patterns, Relationships
2020-02-24	CWE Content Team	MITRE
2020-02-24	updated Potential_Mitigations, References, Relationships
2020-06-25	CWE Content Team	MITRE
2020-06-25	updated Potential_Mitigations
2020-08-20	CWE Content Team	MITRE
2020-08-20	updated Relationships
2020-12-10	CWE Content Team	MITRE
2020-12-10	updated Relationships
2021-03-15	CWE Content Team	MITRE
2021-03-15	updated Relationships
2021-07-20	CWE Content Team	MITRE
2021-07-20	updated Description, Observed_Examples, Relationships
2021-10-28	CWE Content Team	MITRE
2021-10-28	updated Relationships
2022-06-28	CWE Content Team	MITRE
2022-06-28	updated Observed_Examples, Relationships
2022-10-13	CWE Content Team	MITRE
2022-10-13	updated Observed_Examples, References, Terminology_Notes
2023-01-31	CWE Content Team	MITRE
2023-01-31	updated Description, Potential_Mitigations
2023-04-27	CWE Content Team	MITRE
2023-04-27	updated Detection_Factors, Relationships, Time_of_Introduction
2023-06-29	CWE Content Team	MITRE
2023-06-29	updated Mapping_Notes, Relationships
Previous Entry Names
Change Date	Previous Entry Name
2008-04-11	Command Injection

2009-05-27	Failure to Sanitize Data into a Control Plane (aka 'Command Injection')

2009-07-27	Failure to Sanitize Data into a Control Plane ('Command Injection')

2010-06-21	Improper Sanitization of Special Elements used in a Command ('Command Injection')

Weakness ID: 129

View customized information:

Description

Alternate Terms

out-of-bounds array index
index-out-of-range
array index underflow

Relationships

Relevant to the view "Research Concepts" (CWE-1000)

Nature	Type	ID	Name
ChildOf	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	1285	Improper Validation of Specified Index, Position, or Offset in Input
CanPrecede	Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource.	119	Improper Restriction of Operations within the Bounds of a Memory Buffer
CanPrecede	Variant - a weakness that is linked to a certain type of product, typically involving a specific language or technology. More specific than a Base weakness. Variant level weaknesses typically describe issues in terms of 3 to 5 of the following dimensions: behavior, property, technology, language, and resource.	789	Memory Allocation with Excessive Size Value
CanPrecede	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	823	Use of Out-of-range Pointer Offset

Relevant to the view "Weaknesses for Simplified Mapping of Published Vulnerabilities" (CWE-1003)

Nature	Type	ID	Name
ChildOf	Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource.	20	Improper Input Validation

Modes Of Introduction

Phase	Note
Implementation

Applicable Platforms

Languages

C (Often Prevalent)

C++ (Often Prevalent)

Class: Not Language-Specific (Undetermined Prevalence)

Common Consequences

Scope	Impact	Likelihood
Integrity Availability	Technical Impact: DoS: Crash, Exit, or Restart Use of an index that is outside the bounds of an array will very likely result in the corruption of relevant memory and perhaps instructions, leading to a crash, if the values are outside of the valid memory area.
Integrity	Technical Impact: Modify Memory If the memory corrupted is data, rather than instructions, the system will continue to function with improper values.
Confidentiality Integrity	Technical Impact: Modify Memory; Read Memory Use of an index that is outside the bounds of an array can also trigger out-of-bounds read or write operations, or operations on the wrong objects; i.e., "buffer overflows" are not always the result. This may result in the exposure or modification of sensitive data.
Integrity Confidentiality Availability	Technical Impact: Execute Unauthorized Code or Commands If the memory accessible by the attacker can be effectively controlled, it may be possible to execute arbitrary code, as with a standard buffer overflow and possibly without the use of large inputs if a precise index can be controlled.
Integrity Availability Confidentiality	Technical Impact: DoS: Crash, Exit, or Restart; Execute Unauthorized Code or Commands; Read Memory; Modify Memory A single fault could allow either an overflow (CWE-788) or underflow (CWE-786) of the array index. What happens next will depend on the type of operation being performed out of bounds, but can expose sensitive information, cause a system crash, or possibly lead to arbitrary code execution.

Likelihood Of Exploit

High

Demonstrative Examples

Example 1

In the code snippet below, an untrusted integer value is used to reference an object in an array.

(bad code)

Example Language: Java

public String getValue(int index) {

return array[index];

}

If index is outside of the range of the array, this may result in an ArrayIndexOutOfBounds Exception being raised.

Example 2

The following example takes a user-supplied value to allocate an array of objects and then operates on the array.

(bad code)

Example Language: Java

private void buildList ( int untrustedListSize ){

if ( 0 > untrustedListSize ){

die("Negative value supplied for list size, die evil hacker!");

}
Widget[] list = new Widget [ untrustedListSize ];
list[0] = new Widget();

}

This example attempts to build a list from a user-specified value, and even checks to ensure a non-negative value is supplied. If, however, a 0 value is provided, the code will build an array of size 0 and then try to store a new Widget in the first location, causing an exception to be thrown.

Example 3

In the following code, the method retrieves a value from an array at a specific array index location that is given as an input parameter to the method

(bad code)

Example Language: C

int getValueFromArray(int *array, int len, int index) {

int value;

// check that the array index is less than the maximum

// length of the array
if (index < len) {

// get the value at the specified index of the array
value = array[index];

}
// if array index is invalid then output error message

// and return value indicating error
else {

printf("Value is: %d\n", array[index]);
value = -1;

}

return value;

}

However, this method only verifies that the given array index is less than the maximum length of the array but does not check for the minimum value (CWE-839). This will allow a negative value to be accepted as the input array index, which will result in a out of bounds read (CWE-125) and may allow access to sensitive memory. The input array index should be checked to verify that is within the maximum and minimum range required for the array (CWE-129). In this example the if statement should be modified to include a minimum range check, as shown below.

(good code)

Example Language: C

...

// check that the array index is within the correct

// range of values for the array
if (index >= 0 && index < len) {

...

Example 4

The following example retrieves the sizes of messages for a pop3 mail server. The message sizes are retrieved from a socket that returns in a buffer the message number and the message size, the message number (num) and size (size) are extracted from the buffer and the message size is placed into an array using the message number for the array index.

(bad code)

Example Language: C

/* capture the sizes of all messages */
int getsizes(int sock, int count, int *sizes) {

...
char buf[BUFFER_SIZE];
int ok;
int num, size;

// read values from socket and added to sizes array
while ((ok = gen_recv(sock, buf, sizeof(buf))) == 0)
{

// continue read from socket until buf only contains '.'
if (DOTLINE(buf))

break;

else if (sscanf(buf, "%d %d", &num, &size) == 2)

sizes[num - 1] = size;

}

...

}

In this example the message number retrieved from the buffer could be a value that is outside the allowable range of indices for the array and could possibly be a negative number. Without proper validation of the value to be used for the array index an array overflow could occur and could potentially lead to unauthorized access to memory addresses and system crashes. The value of the array index should be validated to ensure that it is within the allowable range of indices for the array as in the following code.

(good code)

Example Language: C

/* capture the sizes of all messages */
int getsizes(int sock, int count, int *sizes) {

...
char buf[BUFFER_SIZE];
int ok;
int num, size;

// read values from socket and added to sizes array
while ((ok = gen_recv(sock, buf, sizeof(buf))) == 0)
{

// continue read from socket until buf only contains '.'
if (DOTLINE(buf))

break;

else if (sscanf(buf, "%d %d", &num, &size) == 2) {

if (num > 0 && num <= (unsigned)count)

sizes[num - 1] = size;

else

/* warn about possible attempt to induce buffer overflow */
report(stderr, "Warning: ignoring bogus data for message sizes returned by server.\n");

}

...

}

Example 5

In the following example the method displayProductSummary is called from a Web service servlet to retrieve product summary information for display to the user. The servlet obtains the integer value of the product number from the user and passes it to the displayProductSummary method. The displayProductSummary method passes the integer value of the product number to the getProductSummary method which obtains the product summary from the array object containing the project summaries using the integer value of the product number as the array index.

(bad code)

Example Language: Java

// Method called from servlet to obtain product information
public String displayProductSummary(int index) {

String productSummary = new String("");

try {

String productSummary = getProductSummary(index);

} catch (Exception ex) {...}

return productSummary;

}

public String getProductSummary(int index) {

return products[index];

}

In this example the integer value used as the array index that is provided by the user may be outside the allowable range of indices for the array which may provide unexpected results or cause the application to fail. The integer value used for the array index should be validated to ensure that it is within the allowable range of indices for the array as in the following code.

(good code)

Example Language: Java

// Method called from servlet to obtain product information
public String displayProductSummary(int index) {

String productSummary = new String("");

try {

String productSummary = getProductSummary(index);

} catch (Exception ex) {...}

return productSummary;

}

public String getProductSummary(int index) {

String productSummary = "";

if ((index >= 0) && (index < MAX_PRODUCTS)) {

productSummary = products[index];

}
else {

System.err.println("index is out of bounds");
throw new IndexOutOfBoundsException();

}

return productSummary;

}

An alternative in Java would be to use one of the collection objects such as ArrayList that will automatically generate an exception if an attempt is made to access an array index that is out of bounds.

(good code)

Example Language: Java

ArrayList productArray = new ArrayList(MAX_PRODUCTS);
...
try {

productSummary = (String) productArray.get(index);

} catch (IndexOutOfBoundsException ex) {...}

Example 6

The following example asks a user for an offset into an array to select an item.

(bad code)

Example Language: C

int main (int argc, char **argv) {

char *items[] = {"boat", "car", "truck", "train"};
int index = GetUntrustedOffset();
printf("You selected %s\n", items[index-1]);

}

The programmer allows the user to specify which element in the list to select, however an attacker can provide an out-of-bounds offset, resulting in a buffer over-read (CWE-126).

Observed Examples

Reference	Description
CVE-2005-0369	large ID in packet used as array index
CVE-2001-1009	negative array index as argument to POP LIST command
CVE-2003-0721	Integer signedness error leads to negative array index
CVE-2004-1189	product does not properly track a count and a maximum number, which can lead to resultant array index overflow.
CVE-2007-5756	Chain: device driver for packet-capturing software allows access to an unintended IOCTL with resultant array index error.
CVE-2005-2456	Chain: array index error (CWE-129) leads to deadlock (CWE-833)

Potential Mitigations

Phase: Architecture and Design

Strategy: Input Validation

Use an input validation framework such as Struts or the OWASP ESAPI Validation API. Note that using a framework does not automatically address all input validation problems; be mindful of weaknesses that could arise from misusing the framework itself (CWE-1173).

Phase: Architecture and Design

Even though client-side checks provide minimal benefits with respect to server-side security, they are still useful. First, they can support intrusion detection. If the server receives input that should have been rejected by the client, then it may be an indication of an attack. Second, client-side error-checking can provide helpful feedback to the user about the expectations for valid input. Third, there may be a reduction in server-side processing time for accidental input errors, although this is typically a small savings.

Phase: Requirements

Strategy: Language Selection

Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.

For example, Ada allows the programmer to constrain the values of a variable and languages such as Java and Ruby will allow the programmer to handle exceptions when an out-of-bounds index is accessed.

Phases: Operation; Build and Compilation

Strategy: Environment Hardening

Run or compile the software using features or extensions that randomly arrange the positions of a program's executable and libraries in memory. Because this makes the addresses unpredictable, it can prevent an attacker from reliably jumping to exploitable code.

Examples include Address Space Layout Randomization (ASLR) [REF-58] [REF-60] and Position-Independent Executables (PIE) [REF-64]. Imported modules may be similarly realigned if their default memory addresses conflict with other modules, in a process known as "rebasing" (for Windows) and "prelinking" (for Linux) [REF-1332] using randomly generated addresses. ASLR for libraries cannot be used in conjunction with prelink since it would require relocating the libraries at run-time, defeating the whole purpose of prelinking.

For more information on these techniques see D3-SAOR (Segment Address Offset Randomization) from D3FEND [REF-1335].

Effectiveness: Defense in Depth

Note: These techniques do not provide a complete solution. For instance, exploits frequently use a bug that discloses memory addresses in order to maximize reliability of code execution [REF-1337]. It has also been shown that a side-channel attack can bypass ASLR [REF-1333]

Phase: Operation

Strategy: Environment Hardening

Use a CPU and operating system that offers Data Execution Protection (using hardware NX or XD bits) or the equivalent techniques that simulate this feature in software, such as PaX [REF-60] [REF-61]. These techniques ensure that any instruction executed is exclusively at a memory address that is part of the code segment.

For more information on these techniques see D3-PSEP (Process Segment Execution Prevention) from D3FEND [REF-1336].

Effectiveness: Defense in Depth

Note: This is not a complete solution, since buffer overflows could be used to overwrite nearby variables to modify the software's state in dangerous ways. In addition, it cannot be used in cases in which self-modifying code is required. Finally, an attack could still cause a denial of service, since the typical response is to exit the application.

Phase: Implementation

Strategy: Input Validation

When accessing a user-controlled array index, use a stringent range of values that are within the target array. Make sure that you do not allow negative values to be used. That is, verify the minimum as well as the maximum of the range of acceptable values.

Phase: Implementation

Be especially careful to validate all input when invoking code that crosses language boundaries, such as from an interpreted language to native code. This could create an unexpected interaction between the language boundaries. Ensure that you are not violating any of the expectations of the language with which you are interfacing. For example, even though Java may not be susceptible to buffer overflows, providing a large argument in a call to native code might trigger an overflow.

Phases: Architecture and Design; Operation

Strategy: Environment Hardening

Phases: Architecture and Design; Operation

Strategy: Sandbox or Jail

This may not be a feasible solution, and it only limits the impact to the operating system; the rest of the application may still be subject to compromise.

Be careful to avoid CWE-243 and other weaknesses related to jails.

Effectiveness: Limited

Weakness Ordinalities

Ordinality

Description

Resultant

(where the weakness is a quality issue that might indirectly make it easier to introduce security-relevant weaknesses or make them more difficult to detect)

The most common condition situation leading to an out-of-bounds array index is the use of loop index variables as buffer indexes. If the end condition for the loop is subject to a flaw, the index can grow or shrink unbounded, therefore causing a buffer overflow or underflow. Another common situation leading to this condition is the use of a function's return value, or the resulting value of a calculation directly as an index in to a buffer.

Detection Methods

Automated Static Analysis

This weakness can often be detected using automated static analysis tools. Many modern tools use data flow analysis or constraint-based techniques to minimize the number of false positives.

Automated static analysis generally does not account for environmental considerations when reporting out-of-bounds memory operations. This can make it difficult for users to determine which warnings should be investigated first. For example, an analysis tool might report array index errors that originate from command line arguments in a program that is not expected to run with setuid or other special privileges.

Effectiveness: High

Note: This is not a perfect solution, since 100% accuracy and coverage are not feasible.

Automated Dynamic Analysis

Black Box

Black box methods might not get the needed code coverage within limited time constraints, and a dynamic test might not produce any noticeable side effects even if it is successful.

Affected Resources

Memory

Memberships

Nature	Type	ID	Name
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	738	CERT C Secure Coding Standard (2008) Chapter 5 - Integers (INT)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	740	CERT C Secure Coding Standard (2008) Chapter 7 - Arrays (ARR)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	802	2010 Top 25 - Risky Resource Management
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	867	2011 Top 25 - Weaknesses On the Cusp
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	872	CERT C++ Secure Coding Section 04 - Integers (INT)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	874	CERT C++ Secure Coding Section 06 - Arrays and the STL (ARR)
MemberOf	View - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries).	884	CWE Cross-section
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	970	SFP Secondary Cluster: Faulty Buffer Access
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1131	CISQ Quality Measures (2016) - Security
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1160	SEI CERT C Coding Standard - Guidelines 06. Arrays (ARR)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1179	SEI CERT Perl Coding Standard - Guidelines 01. Input Validation and Data Sanitization (IDS)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1308	CISQ Quality Measures - Security
MemberOf	View - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries).	1340	CISQ Data Protection Measures
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1399	Comprehensive Categorization: Memory Safety

Vulnerability Mapping Notes

Usage: ALLOWED

(this CWE ID could be used to map to real-world vulnerabilities)

Reason: Acceptable-Use

Rationale:

This CWE entry is at the Variant level of abstraction, which is a preferred level of abstraction for mapping to the root causes of vulnerabilities.

Comments:

Notes

Relationship

This weakness can precede uncontrolled memory allocation (CWE-789) in languages that automatically expand an array when an index is used that is larger than the size of the array, such as JavaScript.

Theoretical

An improperly validated array index might lead directly to the always-incorrect behavior of "access of array using out-of-bounds index."

Taxonomy Mappings

Mapped Taxonomy Name	Node ID	Fit	Mapped Node Name
CLASP			Unchecked array indexing
PLOVER			INDEX - Array index overflow
CERT C Secure Coding	ARR00-C		Understand how arrays work
CERT C Secure Coding	ARR30-C	CWE More Specific	Do not form or use out-of-bounds pointers or array subscripts
CERT C Secure Coding	ARR38-C		Do not add or subtract an integer to a pointer if the resulting value does not refer to a valid array element
CERT C Secure Coding	INT32-C		Ensure that operations on signed integers do not result in overflow
SEI CERT Perl Coding Standard	IDS32-PL	Imprecise	Validate any integer that is used as an array index
OMG ASCSM	ASCSM-CWE-129
Software Fault Patterns	SFP8		Faulty Buffer Access

Related Attack Patterns

CAPEC-ID	Attack Pattern Name
CAPEC-100	Overflow Buffers

References

[REF-7] Michael Howard and David LeBlanc. "Writing Secure Code". Chapter 5, "Array Indexing Errors" Page 144. 2nd Edition. Microsoft Press. 2002-12-04. <https://www.microsoftpressstore.com/store/writing-secure-code-9780735617223>.

[REF-96] Jason Lam. "Top 25 Series - Rank 14 - Improper Validation of Array Index". SANS Software Security Institute. 2010-03-12. <https://web.archive.org/web/20100316064026/http://blogs.sans.org/appsecstreetfighter/2010/03/12/top-25-series-rank-14-improper-validation-of-array-index/>. URL validated: 2023-04-07.

[REF-58] Michael Howard. "Address Space Layout Randomization in Windows Vista". <https://learn.microsoft.com/en-us/archive/blogs/michael_howard/address-space-layout-randomization-in-windows-vista>. URL validated: 2023-04-07.

[REF-60] "PaX". <https://en.wikipedia.org/wiki/Executable_space_protection#PaX>. URL validated: 2023-04-07.

[REF-61] Microsoft. "Understanding DEP as a mitigation technology part 1". <https://msrc.microsoft.com/blog/2009/06/understanding-dep-as-a-mitigation-technology-part-1/>. URL validated: 2023-04-07.

[REF-44] Michael Howard, David LeBlanc and John Viega. "24 Deadly Sins of Software Security". "Sin 5: Buffer Overruns." Page 89. McGraw-Hill. 2010.

[REF-64] Grant Murphy. "Position Independent Executables (PIE)". Red Hat. 2012-11-28. <https://www.redhat.com/en/blog/position-independent-executables-pie>. URL validated: 2023-04-07.

[REF-962] Object Management Group (OMG). "Automated Source Code Security Measure (ASCSM)". ASCSM-CWE-129. 2016-01. <http://www.omg.org/spec/ASCSM/1.0/>.

[REF-18] Secure Software, Inc.. "The CLASP Application Security Process". 2005. <https://cwe.mitre.org/documents/sources/TheCLASPApplicationSecurityProcess.pdf>.

[REF-1332] John Richard Moser. "Prelink and address space randomization". 2006-07-05. <https://lwn.net/Articles/190139/>. URL validated: 2023-04-26.

[REF-1333] Dmitry Evtyushkin, Dmitry Ponomarev, Nael Abu-Ghazaleh. "Jump Over ASLR: Attacking Branch Predictors to Bypass ASLR". 2016. <http://www.cs.ucr.edu/~nael/pubs/micro16.pdf>. URL validated: 2023-04-26.

[REF-1335] D3FEND. "Segment Address Offset Randomization (D3-SAOR)". 2023. <https://d3fend.mitre.org/technique/d3f:SegmentAddressOffsetRandomization/>. URL validated: 2023-04-26.

[REF-1336] D3FEND. "Process Segment Execution Prevention (D3-PSEP)". 2023. <https://d3fend.mitre.org/technique/d3f:ProcessSegmentExecutionPrevention/>. URL validated: 2023-04-26.

[REF-1337] Alexander Sotirov and Mark Dowd. "Bypassing Browser Memory Protections: Setting back browser security by 10 years". Memory information leaks. 2008. <https://www.blackhat.com/presentations/bh-usa-08/Sotirov_Dowd/bh08-sotirov-dowd.pdf>. URL validated: 2023-04-26.

Content History

Submissions
Submission Date	Submitter	Organization
2006-07-19 (CWE Draft 3, 2006-07-19)	CLASP
2006-07-19 (CWE Draft 3, 2006-07-19)
Modifications
Modification Date	Modifier	Organization
2008-07-01	Sean Eidemiller	Cigital
2008-07-01	added/updated demonstrative examples
2008-09-08	CWE Content Team	MITRE
2008-09-08	updated Alternate_Terms, Applicable_Platforms, Common_Consequences, Relationships, Other_Notes, Taxonomy_Mappings, Weakness_Ordinalities
2008-11-24	CWE Content Team	MITRE
2008-11-24	updated Relationships, Taxonomy_Mappings
2009-01-12	CWE Content Team	MITRE
2009-01-12	updated Common_Consequences
2009-10-29	CWE Content Team	MITRE
2009-10-29	updated Description, Name, Relationships
2009-12-28	CWE Content Team	MITRE
2009-12-28	updated Applicable_Platforms, Common_Consequences, Observed_Examples, Other_Notes, Potential_Mitigations, Theoretical_Notes, Weakness_Ordinalities
2010-02-16	CWE Content Team	MITRE
2010-02-16	updated Applicable_Platforms, Demonstrative_Examples, Detection_Factors, Likelihood_of_Exploit, Potential_Mitigations, References, Related_Attack_Patterns, Relationships
2010-04-05	CWE Content Team	MITRE
2010-04-05	updated Related_Attack_Patterns
2010-06-21	CWE Content Team	MITRE
2010-06-21	updated Common_Consequences, Potential_Mitigations, References
2010-09-27	CWE Content Team	MITRE
2010-09-27	updated Potential_Mitigations, Relationship_Notes, Relationships
2010-12-13	CWE Content Team	MITRE
2010-12-13	updated Demonstrative_Examples, Observed_Examples, Potential_Mitigations
2011-03-29	CWE Content Team	MITRE
2011-03-29	updated Common_Consequences, Demonstrative_Examples, Weakness_Ordinalities
2011-06-01	CWE Content Team	MITRE
2011-06-01	updated Common_Consequences
2011-06-27	CWE Content Team	MITRE
2011-06-27	updated Relationships
2011-09-13	CWE Content Team	MITRE
2011-09-13	updated Relationships, Taxonomy_Mappings
2012-05-11	CWE Content Team	MITRE
2012-05-11	updated Demonstrative_Examples, Potential_Mitigations, References, Relationships
2012-10-30	CWE Content Team	MITRE
2012-10-30	updated Potential_Mitigations
2014-02-18	CWE Content Team	MITRE
2014-02-18	updated Potential_Mitigations, References
2014-07-30	CWE Content Team	MITRE
2014-07-30	updated Relationships, Taxonomy_Mappings
2015-12-07	CWE Content Team	MITRE
2015-12-07	updated Relationships
2017-11-08	CWE Content Team	MITRE
2017-11-08	updated Causal_Nature, References, Relationships, Taxonomy_Mappings
2018-03-27	CWE Content Team	MITRE
2018-03-27	updated References
2019-01-03	CWE Content Team	MITRE
2019-01-03	updated References, Relationships, Taxonomy_Mappings
2019-09-19	CWE Content Team	MITRE
2019-09-19	updated Potential_Mitigations
2020-02-24	CWE Content Team	MITRE
2020-02-24	updated Potential_Mitigations, Relationships, Taxonomy_Mappings
2020-06-25	CWE Content Team	MITRE
2020-06-25	updated Demonstrative_Examples, Potential_Mitigations, Relationships, Type
2020-08-20	CWE Content Team	MITRE
2020-08-20	updated Potential_Mitigations, Relationships
2020-12-10	CWE Content Team	MITRE
2020-12-10	updated Relationships
2021-03-15	CWE Content Team	MITRE
2021-03-15	updated References, Relationships
2022-10-13	CWE Content Team	MITRE
2022-10-13	updated References, Relationships, Taxonomy_Mappings
2023-04-27	CWE Content Team	MITRE
2023-04-27	updated Potential_Mitigations, References, Relationships
2023-06-29	CWE Content Team	MITRE
2023-06-29	updated Mapping_Notes
Previous Entry Names
Change Date	Previous Entry Name
2009-10-29	Unchecked Array Indexing

Weakness ID: 705

View customized information:

Description

The product does not properly return control flow to the proper location after it has completed a task or detected an unusual condition.

Relationships

Relevant to the view "Research Concepts" (CWE-1000)

Nature	Type	ID	Name
ChildOf	Pillar - a weakness that is the most abstract type of weakness and represents a theme for all class/base/variant weaknesses related to it. A Pillar is different from a Category as a Pillar is still technically a type of weakness that describes a mistake, while a Category represents a common characteristic used to group related things.	691	Insufficient Control Flow Management
ParentOf	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	248	Uncaught Exception
ParentOf	Variant - a weakness that is linked to a certain type of product, typically involving a specific language or technology. More specific than a Base weakness. Variant level weaknesses typically describe issues in terms of 3 to 5 of the following dimensions: behavior, property, technology, language, and resource.	382	J2EE Bad Practices: Use of System.exit()
ParentOf	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	395	Use of NullPointerException Catch to Detect NULL Pointer Dereference
ParentOf	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	396	Declaration of Catch for Generic Exception
ParentOf	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	397	Declaration of Throws for Generic Exception
ParentOf	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	455	Non-exit on Failed Initialization
ParentOf	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	584	Return Inside Finally Block
ParentOf	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	698	Execution After Redirect (EAR)

Modes Of Introduction

Phase	Note
Implementation

Applicable Platforms

Languages

Class: Not Language-Specific (Undetermined Prevalence)

Common Consequences

Scope	Impact	Likelihood
Other	Technical Impact: Alter Execution Logic; Other

Demonstrative Examples

Example 1

The following example attempts to resolve a hostname.

(bad code)

Example Language: Java

protected void doPost (HttpServletRequest req, HttpServletResponse res) throws IOException {

String ip = req.getRemoteAddr();
InetAddress addr = InetAddress.getByName(ip);
...
out.println("hello " + addr.getHostName());

}

A DNS lookup failure will cause the Servlet to throw an exception.

Example 2

This code queries a server and displays its status when a request comes from an authorized IP address.

(bad code)

Example Language: PHP

$requestingIP = $_SERVER['REMOTE_ADDR'];
if(!in_array($requestingIP,$ipAllowList)){

echo "You are not authorized to view this page";
http_redirect($errorPageURL);

}
$status = getServerStatus();
echo $status;
...

This code redirects unauthorized users, but continues to execute code after calling http_redirect(). This means even unauthorized users may be able to access the contents of the page or perform a DoS attack on the server being queried. Also, note that this code is vulnerable to an IP address spoofing attack (CWE-212).

Example 3

Included in the doPost() method defined below is a call to System.exit() in the event of a specific exception.

(bad code)

Example Language: Java

Public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

try {

...

} catch (ApplicationSpecificException ase) {

logger.error("Caught: " + ase.toString());
System.exit(1);

}

Observed Examples

Reference	Description
CVE-2023-21087	Java code in a smartphone OS can encounter a "boot loop" due to an uncaught exception
CVE-2014-1266	chain: incorrect "goto" in Apple SSL product bypasses certificate validation, allowing Adversary-in-the-Middle (AITM) attack (Apple "goto fail" bug). CWE-705 (Incorrect Control Flow Scoping) -> CWE-561 (Dead Code) -> CWE-295 (Improper Certificate Validation) -> CWE-393 (Return of Wrong Status Code) -> CWE-300 (Channel Accessible by Non-Endpoint).

Memberships

Nature	Type	ID	Name
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	744	CERT C Secure Coding Standard (2008) Chapter 11 - Environment (ENV)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	746	CERT C Secure Coding Standard (2008) Chapter 13 - Error Handling (ERR)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	851	The CERT Oracle Secure Coding Standard for Java (2011) Chapter 8 - Exceptional Behavior (ERR)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	854	The CERT Oracle Secure Coding Standard for Java (2011) Chapter 11 - Thread APIs (THI)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	878	CERT C++ Secure Coding Section 10 - Environment (ENV)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	880	CERT C++ Secure Coding Section 12 - Exceptions and Error Handling (ERR)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	977	SFP Secondary Cluster: Design
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1141	SEI CERT Oracle Secure Coding Standard for Java - Guidelines 07. Exceptional Behavior (ERR)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1147	SEI CERT Oracle Secure Coding Standard for Java - Guidelines 13. Input Output (FIO)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1165	SEI CERT C Coding Standard - Guidelines 10. Environment (ENV)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1181	SEI CERT Perl Coding Standard - Guidelines 03. Expressions (EXP)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1410	Comprehensive Categorization: Insufficient Control Flow Management

Vulnerability Mapping Notes

Usage: ALLOWED-WITH-REVIEW

(this CWE ID could be used to map to real-world vulnerabilities in limited situations requiring careful review)

Reason: Abstraction

Rationale:

This CWE entry is a Class and might have Base-level children that would be more appropriate

Comments:

Examine children of this entry to see if there is a better fit

Taxonomy Mappings

Mapped Taxonomy Name	Node ID	Fit	Mapped Node Name
CERT C Secure Coding	ENV32-C	CWE More Abstract	All exit handlers must return normally
CERT C Secure Coding	ERR04-C		Choose an appropriate termination strategy
The CERT Oracle Secure Coding Standard for Java (2011)	THI05-J		Do not use Thread.stop() to terminate threads
The CERT Oracle Secure Coding Standard for Java (2011)	ERR04-J		Do not complete abruptly from a finally block
The CERT Oracle Secure Coding Standard for Java (2011)	ERR05-J		Do not let checked exceptions escape from a finally block
SEI CERT Perl Coding Standard	EXP31-PL	Imprecise	Do not suppress or ignore exceptions

Content History

Submissions
Submission Date	Submitter	Organization
2008-09-09 (CWE 1.0, 2008-09-09)	CWE Content Team	MITRE
2008-09-09 (CWE 1.0, 2008-09-09)	Note: this date reflects when the entry was first published. Draft versions of this entry were provided to members of the CWE community and modified between Draft 9 and 1.0.
Modifications
Modification Date	Modifier	Organization
2008-07-01	Eric Dalci	Cigital
2008-07-01	updated Time_of_Introduction
2008-11-24	CWE Content Team	MITRE
2008-11-24	updated Relationships, Taxonomy_Mappings
2011-03-29	CWE Content Team	MITRE
2011-03-29	updated Relationships
2011-06-01	CWE Content Team	MITRE
2011-06-01	updated Common_Consequences, Relationships, Taxonomy_Mappings
2011-09-13	CWE Content Team	MITRE
2011-09-13	updated Relationships, Taxonomy_Mappings
2012-05-11	CWE Content Team	MITRE
2012-05-11	updated Relationships, Taxonomy_Mappings
2014-06-23	CWE Content Team	MITRE
2014-06-23	updated Observed_Examples
2014-07-30	CWE Content Team	MITRE
2014-07-30	updated Relationships
2017-01-19	CWE Content Team	MITRE
2017-01-19	updated Relationships
2017-11-08	CWE Content Team	MITRE
2017-11-08	updated Applicable_Platforms, Relationships, Taxonomy_Mappings
2019-01-03	CWE Content Team	MITRE
2019-01-03	updated Relationships, Taxonomy_Mappings
2020-02-24	CWE Content Team	MITRE
2020-02-24	updated Observed_Examples, Relationships
2021-03-15	CWE Content Team	MITRE
2021-03-15	updated Relationships
2021-07-20	CWE Content Team	MITRE
2021-07-20	updated Observed_Examples
2023-01-31	CWE Content Team	MITRE
2023-01-31	updated Description
2023-04-27	CWE Content Team	MITRE
2023-04-27	updated Relationships, Time_of_Introduction
2023-06-29	CWE Content Team	MITRE
2023-06-29	updated Mapping_Notes
2024-02-29 (CWE 4.14, 2024-02-29)	CWE Content Team	MITRE
2024-02-29 (CWE 4.14, 2024-02-29)	updated Demonstrative_Examples, Observed_Examples

Weakness ID: 789

View customized information:

Description

The product allocates memory based on an untrusted, large size value, but it does not ensure that the size is within expected limits, allowing arbitrary amounts of memory to be allocated.

Alternate Terms

Stack Exhaustion:	When a weakness allocates excessive memory on the stack, it is often described as "stack exhaustion," which is a technical impact of the weakness. This technical impact is often encountered as a consequence of CWE-789 and/or CWE-1325.

Relationships

Relevant to the view "Research Concepts" (CWE-1000)

Nature	Type	ID	Name
ChildOf	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	770	Allocation of Resources Without Limits or Throttling
PeerOf	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	1325	Improperly Controlled Sequential Memory Allocation
CanFollow	Variant - a weakness that is linked to a certain type of product, typically involving a specific language or technology. More specific than a Base weakness. Variant level weaknesses typically describe issues in terms of 3 to 5 of the following dimensions: behavior, property, technology, language, and resource.	129	Improper Validation of Array Index
CanFollow	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	1284	Improper Validation of Specified Quantity in Input
CanPrecede	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	476	NULL Pointer Dereference

Modes Of Introduction

Phase	Note
Implementation

Applicable Platforms

Languages

C (Undetermined Prevalence)

C++ (Undetermined Prevalence)

Class: Not Language-Specific (Undetermined Prevalence)

Common Consequences

Scope	Impact	Likelihood
Availability	Technical Impact: DoS: Resource Consumption (Memory) Not controlling memory allocation can result in a request for too much system memory, possibly leading to a crash of the application due to out-of-memory conditions, or the consumption of a large amount of memory on the system.

Demonstrative Examples

Example 1

Consider the following code, which accepts an untrusted size value and allocates a buffer to contain a string of the given size.

(bad code)

Example Language: C

unsigned int size = GetUntrustedInt();
/* ignore integer overflow (CWE-190) for this example */

unsigned int totBytes = size * sizeof(char);
char *string = (char *)malloc(totBytes);
InitializeString(string);

Suppose an attacker provides a size value of:

12345678

This will cause 305,419,896 bytes (over 291 megabytes) to be allocated for the string.

Example 2

Consider the following code, which accepts an untrusted size value and uses the size as an initial capacity for a HashMap.

(bad code)

Example Language: Java

unsigned int size = GetUntrustedInt();
HashMap list = new HashMap(size);

The HashMap constructor will verify that the initial capacity is not negative, however there is no check in place to verify that sufficient memory is present. If the attacker provides a large enough value, the application will run into an OutOfMemoryError.

Example 3

This code performs a stack allocation based on a length calculation.

(bad code)

Example Language: C

int a = 5, b = 6;
size_t len = a - b;
char buf[len]; // Just blows up the stack

}

Since a and b are declared as signed ints, the "a - b" subtraction gives a negative result (-1). However, since len is declared to be unsigned, len is cast to an extremely large positive number (on 32-bit systems - 4294967295). As a result, the buffer buf[len] declaration uses an extremely large size to allocate on the stack, very likely more than the entire computer's memory space.

Miscalculations usually will not be so obvious. The calculation will either be complicated or the result of an attacker's input to attain the negative value.

Example 4

This example shows a typical attempt to parse a string with an error resulting from a difference in assumptions between the caller to a function and the function's action.

(bad code)

Example Language: C

int proc_msg(char *s, int msg_len)
{

// Note space at the end of the string - assume all strings have preamble with space
int pre_len = sizeof("preamble: ");
char buf[pre_len - msg_len];
... Do processing here if we get this far

}
char *s = "preamble: message\n";
char *sl = strchr(s, ':'); // Number of characters up to ':' (not including space)
int jnklen = sl == NULL ? 0 : sl - s; // If undefined pointer, use zero length
int ret_val = proc_msg ("s", jnklen); // Violate assumption of preamble length, end up with negative value, blow out stack

The buffer length ends up being -1, resulting in a blown out stack. The space character after the colon is included in the function calculation, but not in the caller's calculation. This, unfortunately, is not usually so obvious but exists in an obtuse series of calculations.

Example 5

The following code obtains an untrusted number that is used as an index into an array of messages.

(bad code)

Example Language: Perl

my $num = GetUntrustedNumber();
my @messages = ();

$messages[$num] = "Hello World";

The index is not validated at all (CWE-129), so it might be possible for an attacker to modify an element in @messages that was not intended. If an index is used that is larger than the current size of the array, the Perl interpreter automatically expands the array so that the large index works.

If $num is a large value such as 2147483648 (1<<31), then the assignment to $messages[$num] would attempt to create a very large array, then eventually produce an error message such as:

Out of memory during array extend

This memory exhaustion will cause the Perl program to exit, possibly a denial of service. In addition, the lack of memory could also prevent many other programs from successfully running on the system.

Example 6

This example shows a typical attempt to parse a string with an error resulting from a difference in assumptions between the caller to a function and the function's action. The buffer length ends up being -1 resulting in a blown out stack. The space character after the colon is included in the function calculation, but not in the caller's calculation. This, unfortunately, is not usually so obvious but exists in an obtuse series of calculations.

(bad code)

Example Language: C

int proc_msg(char *s, int msg_len)
{

int pre_len = sizeof("preamble: "); // Note space at the end of the string - assume all strings have preamble with space

char buf[pre_len - msg_len];

... Do processing here and set status

return status;

(good code)

Example Language: C

int proc_msg(char *s, int msg_len)
{

int pre_len = sizeof("preamble: "); // Note space at the end of the string - assume all strings have preamble with space

if (pre_len <= msg_len) { // Log error; return error_code; }

char buf[pre_len - msg_len];

... Do processing here and set status

return status;

Observed Examples

Reference	Description
CVE-2022-21668	Chain: Python library does not limit the resources used to process images that specify a very large number of bands (CWE-1284), leading to excessive memory consumption (CWE-789) or an integer overflow (CWE-190).
CVE-2010-3701	program uses ::alloca() for encoding messages, but large messages trigger segfault
CVE-2008-1708	memory consumption and daemon exit by specifying a large value in a length field
CVE-2008-0977	large value in a length field leads to memory consumption and crash when no more memory is available
CVE-2006-3791	large key size in game program triggers crash when a resizing function cannot allocate enough memory
CVE-2004-2589	large Content-Length HTTP header value triggers application crash in instant messaging application due to failure in memory allocation

Potential Mitigations

Phases: Implementation; Architecture and Design

Perform adequate input validation against any value that influences the amount of memory that is allocated. Define an appropriate strategy for handling requests that exceed the limit, and consider supporting a configuration option so that the administrator can extend the amount of memory to be used if necessary.

Phase: Operation

Run your program using system-provided resource limits for memory. This might still cause the program to crash or exit, but the impact to the rest of the system will be minimized.

Weakness Ordinalities

Ordinality	Description
Primary	(where the weakness exists independent of other weaknesses)
Resultant	(where the weakness is typically related to the presence of some other weaknesses)

Detection Methods

Fuzzing

Fuzz testing (fuzzing) is a powerful technique for generating large numbers of diverse inputs - either randomly or algorithmically - and dynamically invoking the code with those inputs. Even with random inputs, it is often capable of generating unexpected results such as crashes, memory corruption, or resource consumption. Fuzzing effectively produces repeatable test cases that clearly indicate bugs, which helps developers to diagnose the issues.

Effectiveness: High

Automated Static Analysis

Effectiveness: High

Memberships

Nature	Type	ID	Name
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1131	CISQ Quality Measures (2016) - Security
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1162	SEI CERT C Coding Standard - Guidelines 08. Memory Management (MEM)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1179	SEI CERT Perl Coding Standard - Guidelines 01. Input Validation and Data Sanitization (IDS)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1308	CISQ Quality Measures - Security
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1399	Comprehensive Categorization: Memory Safety

Vulnerability Mapping Notes

Usage: ALLOWED

(this CWE ID could be used to map to real-world vulnerabilities)

Reason: Acceptable-Use

Rationale:

This CWE entry is at the Variant level of abstraction, which is a preferred level of abstraction for mapping to the root causes of vulnerabilities.

Comments:

Notes

Relationship

This weakness can be closely associated with integer overflows (CWE-190). Integer overflow attacks would concentrate on providing an extremely large number that triggers an overflow that causes less memory to be allocated than expected. By providing a large value that does not trigger an integer overflow, the attacker could still cause excessive amounts of memory to be allocated.

Applicable Platform

Uncontrolled memory allocation is possible in many languages, such as dynamic array allocation in perl or initial size parameters in Collections in Java. However, languages like C and C++ where programmers have the power to more directly control memory management will be more susceptible.

Taxonomy Mappings

Mapped Taxonomy Name	Node ID	Fit	Mapped Node Name
WASC	35		SOAP Array Abuse
CERT C Secure Coding	MEM35-C	Imprecise	Allocate sufficient memory for an object
SEI CERT Perl Coding Standard	IDS32-PL	Imprecise	Validate any integer that is used as an array index
OMG ASCSM	ASCSM-CWE-789

References

[REF-62] Mark Dowd, John McDonald and Justin Schuh. "The Art of Software Security Assessment". Chapter 10, "Resource Limits", Page 574. 1st Edition. Addison Wesley. 2006.

[REF-962] Object Management Group (OMG). "Automated Source Code Security Measure (ASCSM)". ASCSM-CWE-789. 2016-01. <http://www.omg.org/spec/ASCSM/1.0/>.

Content History

Submissions
Submission Date	Submitter	Organization
2009-10-21 (CWE 1.6, 2009-10-29)	CWE Content Team	MITRE
2009-10-21 (CWE 1.6, 2009-10-29)
Modifications
Modification Date	Modifier	Organization
2010-02-16	CWE Content Team	MITRE
2010-02-16	updated Taxonomy_Mappings
2011-03-29	CWE Content Team	MITRE
2011-03-29	updated Common_Consequences, Observed_Examples
2011-06-01	CWE Content Team	MITRE
2011-06-01	updated Common_Consequences
2012-05-11	CWE Content Team	MITRE
2012-05-11	updated References
2017-11-08	CWE Content Team	MITRE
2017-11-08	updated Applicable_Platforms, Taxonomy_Mappings
2019-01-03	CWE Content Team	MITRE
2019-01-03	updated References, Relationships, Taxonomy_Mappings
2019-06-20	CWE Content Team	MITRE
2019-06-20	updated Relationships
2020-02-24	CWE Content Team	MITRE
2020-02-24	updated Relationships
2020-06-25	CWE Content Team	MITRE
2020-06-25	updated Relationships
2020-08-20	CWE Content Team	MITRE
2020-08-20	updated Relationships
2020-12-10	CWE Content Team	MITRE
2020-12-10	updated Alternate_Terms, Demonstrative_Examples, Description, Likelihood_of_Exploit, Name, Observed_Examples, Relationships, Time_of_Introduction
2021-03-15	CWE Content Team	MITRE
2021-03-15	updated Demonstrative_Examples, Relationships
2022-10-13	CWE Content Team	MITRE
2022-10-13	updated Observed_Examples
2023-04-27	CWE Content Team	MITRE
2023-04-27	updated Detection_Factors, Relationships
2023-06-29	CWE Content Team	MITRE
2023-06-29	updated Mapping_Notes, Relationships
Previous Entry Names
Change Date	Previous Entry Name
2020-12-10	Uncontrolled Memory Allocation

Weakness ID: 456

View customized information:

Description

The product does not initialize critical variables, which causes the execution environment to use unexpected values.

Relationships

Relevant to the view "Research Concepts" (CWE-1000)

Nature	Type	ID	Name
ChildOf	Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource.	909	Missing Initialization of Resource
CanPrecede	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	89	Improper Neutralization of Special Elements used in an SQL Command ('SQL Injection')
CanPrecede	Variant - a weakness that is linked to a certain type of product, typically involving a specific language or technology. More specific than a Base weakness. Variant level weaknesses typically describe issues in terms of 3 to 5 of the following dimensions: behavior, property, technology, language, and resource.	98	Improper Control of Filename for Include/Require Statement in PHP Program ('PHP Remote File Inclusion')
CanPrecede	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	120	Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')
CanPrecede	Variant - a weakness that is linked to a certain type of product, typically involving a specific language or technology. More specific than a Base weakness. Variant level weaknesses typically describe issues in terms of 3 to 5 of the following dimensions: behavior, property, technology, language, and resource.	457	Use of Uninitialized Variable

Relevant to the view "CISQ Quality Measures (2020)" (CWE-1305)

Nature	Type	ID	Name
ChildOf	Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource.	665	Improper Initialization

Relevant to the view "CISQ Data Protection Measures" (CWE-1340)

Nature	Type	ID	Name
ChildOf	Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource.	665	Improper Initialization

Modes Of Introduction

Phase	Note
Implementation

Applicable Platforms

Languages

Class: Not Language-Specific (Undetermined Prevalence)

Common Consequences

Scope	Impact	Likelihood
Integrity Other	Technical Impact: Unexpected State; Quality Degradation; Varies by Context The uninitialized data may be invalid, causing logic errors within the program. In some cases, this could result in a security problem.

Demonstrative Examples

Example 1

This function attempts to extract a pair of numbers from a user-supplied string.

(bad code)

Example Language: C

void parse_data(char *untrusted_input){

int m, n, error;
error = sscanf(untrusted_input, "%d:%d", &m, &n);
if ( EOF == error ){

die("Did not specify integer value. Die evil hacker!\n");

}
/* proceed assuming n and m are initialized correctly */

}

This code attempts to extract two integer values out of a formatted, user-supplied input. However, if an attacker were to provide an input of the form:

(attack code)

123:

then only the m variable will be initialized. Subsequent use of n may result in the use of an uninitialized variable (CWE-457).

Example 2

Here, an uninitialized field in a Java class is used in a seldom-called method, which would cause a NullPointerException to be thrown.

(bad code)

Example Language: Java

private User user;
public void someMethod() {

// Do something interesting.
...

// Throws NPE if user hasn't been properly initialized.
String username = user.getName();

}

Example 3

This code first authenticates a user, then allows a delete command if the user is an administrator.

(bad code)

Example Language: PHP

if (authenticate($username,$password) && setAdmin($username)){

$isAdmin = true;

}
/.../

if ($isAdmin){

deleteUser($userToDelete);

}

The $isAdmin variable is set to true if the user is an admin, but is uninitialized otherwise. If PHP's register_globals feature is enabled, an attacker can set uninitialized variables like $isAdmin to arbitrary values, in this case gaining administrator privileges by setting $isAdmin to true.

Example 4

In the following Java code the BankManager class uses the user variable of the class User to allow authorized users to perform bank manager tasks. The user variable is initialized within the method setUser that retrieves the User from the User database. The user is then authenticated as unauthorized user through the method authenticateUser.

(bad code)

Example Language: Java

public class BankManager {

// user allowed to perform bank manager tasks
private User user = null;
private boolean isUserAuthentic = false;

// constructor for BankManager class
public BankManager() {

...

}

// retrieve user from database of users
public User getUserFromUserDatabase(String username){

...

}

// set user variable using username
public void setUser(String username) {

this.user = getUserFromUserDatabase(username);

}

// authenticate user
public boolean authenticateUser(String username, String password) {

if (username.equals(user.getUsername()) && password.equals(user.getPassword())) {

isUserAuthentic = true;

}
return isUserAuthentic;

}

// methods for performing bank manager tasks
...

}

However, if the method setUser is not called before authenticateUser then the user variable will not have been initialized and will result in a NullPointerException. The code should verify that the user variable has been initialized before it is used, as in the following code.

(good code)

Example Language: Java

public class BankManager {

// user allowed to perform bank manager tasks
private User user = null;
private boolean isUserAuthentic = false;

// constructor for BankManager class
public BankManager(String username) {

user = getUserFromUserDatabase(username);

}

// retrieve user from database of users
public User getUserFromUserDatabase(String username) {...}

// authenticate user
public boolean authenticateUser(String username, String password) {

if (user == null) {

System.out.println("Cannot find user " + username);

}
else {

if (password.equals(user.getPassword())) {

isUserAuthentic = true;

}

}
return isUserAuthentic;

}

// methods for performing bank manager tasks
...

}

Example 5

This example will leave test_string in an unknown condition when i is the same value as err_val, because test_string is not initialized (CWE-456). Depending on where this code segment appears (e.g. within a function body), test_string might be random if it is stored on the heap or stack. If the variable is declared in static memory, it might be zero or NULL. Compiler optimization might contribute to the unpredictability of this address.

(bad code)

Example Language: C

char *test_string;
if (i != err_val)
{

test_string = "Hello World!";

}
printf("%s", test_string);

When the printf() is reached, test_string might be an unexpected address, so the printf might print junk strings (CWE-457).

To fix this code, there are a couple approaches to making sure that test_string has been properly set once it reaches the printf().

One solution would be to set test_string to an acceptable default before the conditional:

(good code)

Example Language: C

char *test_string = "Done at the beginning";
if (i != err_val)
{

test_string = "Hello World!";

}
printf("%s", test_string);

Another solution is to ensure that each branch of the conditional - including the default/else branch - could ensure that test_string is set:

(good code)

Example Language: C

char *test_string;
if (i != err_val)
{

test_string = "Hello World!";

}
else {

test_string = "Done on the other side!";

}
printf("%s", test_string);

Observed Examples

Reference	Description
CVE-2020-6078	Chain: The return value of a function returning a pointer is not checked for success (CWE-252) resulting in the later use of an uninitialized variable (CWE-456) and a null pointer dereference (CWE-476)
CVE-2009-2692	Chain: Use of an unimplemented network socket operation pointing to an uninitialized handler function (CWE-456) causes a crash because of a null pointer dereference (CWE-476).
CVE-2020-20739	A variable that has its value set in a conditional statement is sometimes used when the conditional fails, sometimes causing data leakage
CVE-2005-2978	Product uses uninitialized variables for size and index, leading to resultant buffer overflow.
CVE-2005-2109	Internal variable in PHP application is not initialized, allowing external modification.
CVE-2005-2193	Array variable not initialized in PHP application, leading to resultant SQL injection.

Potential Mitigations

Phase: Implementation

Check that critical variables are initialized.

Phase: Testing

Use a static analysis tool to spot non-initialized variables.

Detection Methods

Automated Static Analysis

Effectiveness: High

Memberships

Nature	Type	ID	Name
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	808	2010 Top 25 - Weaknesses On the Cusp
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	867	2011 Top 25 - Weaknesses On the Cusp
MemberOf	View - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries).	884	CWE Cross-section
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	998	SFP Secondary Cluster: Glitch in Computation
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1129	CISQ Quality Measures (2016) - Reliability
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1131	CISQ Quality Measures (2016) - Security
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1167	SEI CERT C Coding Standard - Guidelines 12. Error Handling (ERR)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1180	SEI CERT Perl Coding Standard - Guidelines 02. Declarations and Initialization (DCL)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1416	Comprehensive Categorization: Resource Lifecycle Management

Vulnerability Mapping Notes

Usage: ALLOWED

(this CWE ID could be used to map to real-world vulnerabilities)

Reason: Acceptable-Use

Rationale:

This CWE entry is at the Variant level of abstraction, which is a preferred level of abstraction for mapping to the root causes of vulnerabilities.

Comments:

Notes

Relationship

This weakness is a major factor in a number of resultant weaknesses, especially in web applications that allow global variable initialization (such as PHP) with libraries that can be directly requested.

Research Gap

It is highly likely that a large number of resultant weaknesses have missing initialization as a primary factor, but researcher reports generally do not provide this level of detail.

Taxonomy Mappings

Mapped Taxonomy Name	Node ID	Fit	Mapped Node Name
PLOVER			Missing Initialization
Software Fault Patterns	SFP1		Glitch in computation
CERT C Secure Coding	ERR30-C	CWE More Abstract	Set errno to zero before calling a library function known to set errno, and check errno only after the function returns a value indicating failure
SEI CERT Perl Coding Standard	DCL04-PL	Exact	Always initialize local variables
SEI CERT Perl Coding Standard	DCL33-PL	Imprecise	Declare identifiers before using them
OMG ASCSM	ASCSM-CWE-456
OMG ASCRM	ASCRM-CWE-456

References

[REF-62] Mark Dowd, John McDonald and Justin Schuh. "The Art of Software Security Assessment". Chapter 7, "Variable Initialization", Page 312. 1st Edition. Addison Wesley. 2006.

[REF-961] Object Management Group (OMG). "Automated Source Code Reliability Measure (ASCRM)". ASCRM-CWE-456. 2016-01. <http://www.omg.org/spec/ASCRM/1.0/>.

[REF-962] Object Management Group (OMG). "Automated Source Code Security Measure (ASCSM)". ASCSM-CWE-456. 2016-01. <http://www.omg.org/spec/ASCSM/1.0/>.

Content History

Submissions
Submission Date	Submitter	Organization
2006-07-19 (CWE Draft 3, 2006-07-19)	PLOVER
2006-07-19 (CWE Draft 3, 2006-07-19)
Modifications
Modification Date	Modifier	Organization
2008-07-01	Sean Eidemiller	Cigital
2008-07-01	added/updated demonstrative examples
2008-07-01	Eric Dalci	Cigital
2008-07-01	updated Potential_Mitigations, Time_of_Introduction
2008-09-08	CWE Content Team	MITRE
2008-09-08	updated Relationships, Other_Notes, Taxonomy_Mappings
2010-02-16	CWE Content Team	MITRE
2010-02-16	updated Relationships
2010-04-05	CWE Content Team	MITRE
2010-04-05	updated Applicable_Platforms, Demonstrative_Examples
2010-06-21	CWE Content Team	MITRE
2010-06-21	updated Other_Notes, Relationship_Notes
2011-03-29	CWE Content Team	MITRE
2011-03-29	updated Demonstrative_Examples
2011-06-01	CWE Content Team	MITRE
2011-06-01	updated Common_Consequences
2011-06-27	CWE Content Team	MITRE
2011-06-27	updated Common_Consequences, Relationships
2012-05-11	CWE Content Team	MITRE
2012-05-11	updated References, Relationships
2012-10-30	CWE Content Team	MITRE
2012-10-30	updated Potential_Mitigations
2013-02-21	CWE Content Team	MITRE
2013-02-21	updated Name, Relationships
2014-07-30	CWE Content Team	MITRE
2014-07-30	updated Relationships, Taxonomy_Mappings
2017-11-08	CWE Content Team	MITRE
2017-11-08	updated Taxonomy_Mappings
2019-01-03	CWE Content Team	MITRE
2019-01-03	updated References, Relationships, Taxonomy_Mappings
2019-06-20	CWE Content Team	MITRE
2019-06-20	updated Relationships, Type
2020-02-24	CWE Content Team	MITRE
2020-02-24	updated Relationships
2020-06-25	CWE Content Team	MITRE
2020-06-25	updated Demonstrative_Examples
2020-08-20	CWE Content Team	MITRE
2020-08-20	updated Relationships
2020-12-10	CWE Content Team	MITRE
2020-12-10	updated Relationships
2021-03-15	CWE Content Team	MITRE
2021-03-15	updated Demonstrative_Examples, Observed_Examples, Relationships
2023-01-31	CWE Content Team	MITRE
2023-01-31	updated Description
2023-04-27	CWE Content Team	MITRE
2023-04-27	updated Detection_Factors, Relationships
2023-06-29	CWE Content Team	MITRE
2023-06-29	updated Mapping_Notes
Previous Entry Names
Change Date	Previous Entry Name
2013-02-21	Missing Initialization

Weakness ID: 783

View customized information:

Description

The product uses an expression in which operator precedence causes incorrect logic to be used.

Extended Description

While often just a bug, operator precedence logic errors can have serious consequences if they are used in security-critical code, such as making an authentication decision.

Relationships

Relevant to the view "Research Concepts" (CWE-1000)

Nature	Type	ID	Name
ChildOf	Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource.	670	Always-Incorrect Control Flow Implementation

Relevant to the view "Software Development" (CWE-699)

Nature	Type	ID	Name
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	438	Behavioral Problems
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	569	Expression Issues

Modes Of Introduction

Phase	Note
Implementation	Logic errors related to operator precedence may cause problems even during normal operation, so they are probably discovered quickly during the testing phase. If testing is incomplete or there is a strong reliance on manual review of the code, then these errors may not be discovered before the software is deployed.

Applicable Platforms

Languages

C (Rarely Prevalent)

C++ (Rarely Prevalent)

Class: Not Language-Specific (Rarely Prevalent)

Common Consequences

Scope	Impact	Likelihood
Confidentiality Integrity Availability	Technical Impact: Varies by Context; Unexpected State The consequences will vary based on the context surrounding the incorrect precedence. In a security decision, integrity or confidentiality are the most likely results. Otherwise, a crash may occur due to the software reaching an unexpected state.

Likelihood Of Exploit

Low

Demonstrative Examples

Example 1

In the following example, the method validateUser makes a call to another method to authenticate a username and password for a user and returns a success or failure code.

(bad code)

Example Language: C

#define FAIL 0
#define SUCCESS 1

...

int validateUser(char *username, char *password) {

int isUser = FAIL;

// call method to authenticate username and password

// if authentication fails then return failure otherwise return success
if (isUser = AuthenticateUser(username, password) == FAIL) {

return isUser;

}
else {

isUser = SUCCESS;

}

return isUser;

}

However, the method that authenticates the username and password is called within an if statement with incorrect operator precedence logic. Because the comparison operator "==" has a higher precedence than the assignment operator "=", the comparison operator will be evaluated first and if the method returns FAIL then the comparison will be true, the return variable will be set to true and SUCCESS will be returned. This operator precedence logic error can be easily resolved by properly using parentheses within the expression of the if statement, as shown below.

(good code)

Example Language: C

...

if ((isUser = AuthenticateUser(username, password)) == FAIL) {

...

Example 2

In this example, the method calculates the return on investment for an accounting/financial application. The return on investment is calculated by subtracting the initial investment costs from the current value and then dividing by the initial investment costs.

(bad code)

Example Language: Java

public double calculateReturnOnInvestment(double currentValue, double initialInvestment) {

double returnROI = 0.0;

// calculate return on investment
returnROI = currentValue - initialInvestment / initialInvestment;

return returnROI;

}

However, the return on investment calculation will not produce correct results because of the incorrect operator precedence logic in the equation. The divide operator has a higher precedence than the minus operator, therefore the equation will divide the initial investment costs by the initial investment costs which will only subtract one from the current value. Again this operator precedence logic error can be resolved by the correct use of parentheses within the equation, as shown below.

(good code)

Example Language: Java

...

returnROI = (currentValue - initialInvestment) / initialInvestment;

...

Note that the initialInvestment variable in this example should be validated to ensure that it is greater than zero to avoid a potential divide by zero error (CWE-369).

Observed Examples

Reference	Description
CVE-2008-2516	Authentication module allows authentication bypass because it uses "(x = call(args) == SUCCESS)" instead of "((x = call(args)) == SUCCESS)".
CVE-2008-0599	Chain: Language interpreter calculates wrong buffer size (CWE-131) by using "size = ptr ? X : Y" instead of "size = (ptr ? X : Y)" expression.
CVE-2001-1155	Chain: product does not properly check the result of a reverse DNS lookup because of operator precedence (CWE-783), allowing bypass of DNS-based access restrictions.

Potential Mitigations

Phase: Implementation

Regularly wrap sub-expressions in parentheses, especially in security-critical code.

Memberships

Nature	Type	ID	Name
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	737	CERT C Secure Coding Standard (2008) Chapter 4 - Expressions (EXP)
MemberOf	View - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries).	884	CWE Cross-section
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1181	SEI CERT Perl Coding Standard - Guidelines 03. Expressions (EXP)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1307	CISQ Quality Measures - Maintainability
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1308	CISQ Quality Measures - Security
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1410	Comprehensive Categorization: Insufficient Control Flow Management

Vulnerability Mapping Notes

Usage: ALLOWED

(this CWE ID could be used to map to real-world vulnerabilities)

Reason: Acceptable-Use

Rationale:

This CWE entry is at the Base level of abstraction, which is a preferred level of abstraction for mapping to the root causes of vulnerabilities.

Comments:

Taxonomy Mappings

Mapped Taxonomy Name	Node ID	Fit	Mapped Node Name
CERT C Secure Coding	EXP00-C	Exact	Use parentheses for precedence of operation
SEI CERT Perl Coding Standard	EXP04-PL	CWE More Abstract	Do not mix the early-precedence logical operators with late-precedence logical operators

References

[REF-704] CERT. "EXP00-C. Use parentheses for precedence of operation". <https://www.securecoding.cert.org/confluence/display/seccode/EXP00-C.+Use+parentheses+for+precedence+of+operation>.

[REF-62] Mark Dowd, John McDonald and Justin Schuh. "The Art of Software Security Assessment". Chapter 6, "Precedence", Page 287. 1st Edition. Addison Wesley. 2006.

Content History

Submissions
Submission Date	Submitter	Organization
2009-07-16 (CWE 1.5, 2009-07-27)	CWE Content Team	MITRE
2009-07-16 (CWE 1.5, 2009-07-27)
Modifications
Modification Date	Modifier	Organization
2009-12-28	CWE Content Team	MITRE
2009-12-28	updated Observed_Examples
2011-06-27	CWE Content Team	MITRE
2011-06-27	updated Common_Consequences
2012-05-11	CWE Content Team	MITRE
2012-05-11	updated Demonstrative_Examples, References, Relationships
2017-11-08	CWE Content Team	MITRE
2017-11-08	updated Taxonomy_Mappings, Time_of_Introduction
2019-01-03	CWE Content Team	MITRE
2019-01-03	updated Taxonomy_Mappings
2019-06-20	CWE Content Team	MITRE
2019-06-20	updated Type
2020-02-24	CWE Content Team	MITRE
2020-02-24	updated Relationships
2020-08-20	CWE Content Team	MITRE
2020-08-20	updated Relationships
2021-03-15	CWE Content Team	MITRE
2021-03-15	updated Relationships
2023-01-31	CWE Content Team	MITRE
2023-01-31	updated Description
2023-04-27	CWE Content Team	MITRE
2023-04-27	updated Relationships
2023-06-29	CWE Content Team	MITRE
2023-06-29	updated Mapping_Notes

Weakness ID: 375

View customized information:

Description

Sending non-cloned mutable data as a return value may result in that data being altered or deleted by the calling function.

Extended Description

In situations where functions return references to mutable data, it is possible that the external code which called the function may make changes to the data sent. If this data was not previously cloned, the class will then be using modified data which may violate assumptions about its internal state.

Relationships

Relevant to the view "Research Concepts" (CWE-1000)

Nature	Type	ID	Name
ChildOf	Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource.	668	Exposure of Resource to Wrong Sphere

Relevant to the view "Software Development" (CWE-699)

Nature	Type	ID	Name
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	371	State Issues

Modes Of Introduction

Phase	Note
Implementation

Applicable Platforms

Languages

C (Undetermined Prevalence)

C++ (Undetermined Prevalence)

Java (Undetermined Prevalence)

C# (Undetermined Prevalence)

Common Consequences

Scope	Impact	Likelihood
Access Control Integrity	Technical Impact: Modify Memory Potentially data could be tampered with by another function which should not have been tampered with.

Likelihood Of Exploit

Medium

Demonstrative Examples

Example 1

This class has a private list of patients, but provides a way to see the list :

(bad code)

Example Language: Java

public class ClinicalTrial {

private PatientClass[] patientList = new PatientClass[50];
public getPatients(...){

return patientList;

}

While this code only means to allow reading of the patient list, the getPatients() method returns a reference to the class's original patient list instead of a reference to a copy of the list. Any caller of this method can arbitrarily modify the contents of the patient list even though it is a private member of the class.

Potential Mitigations

Phase: Implementation

Declare returned data which should not be altered as constant or immutable.

Phase: Implementation

Clone all mutable data before returning references to it. This is the preferred mitigation. This way, regardless of what changes are made to the data, a valid copy is retained for use by the class.

Memberships

Nature	Type	ID	Name
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	849	The CERT Oracle Secure Coding Standard for Java (2011) Chapter 6 - Object Orientation (OBJ)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	963	SFP Secondary Cluster: Exposed Data
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1139	SEI CERT Oracle Secure Coding Standard for Java - Guidelines 05. Object Orientation (OBJ)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1181	SEI CERT Perl Coding Standard - Guidelines 03. Expressions (EXP)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1403	Comprehensive Categorization: Exposed Resource

Vulnerability Mapping Notes

Usage: ALLOWED

(this CWE ID could be used to map to real-world vulnerabilities)

Reason: Acceptable-Use

Rationale:

This CWE entry is at the Base level of abstraction, which is a preferred level of abstraction for mapping to the root causes of vulnerabilities.

Comments:

Taxonomy Mappings

Mapped Taxonomy Name	Node ID	Fit	Mapped Node Name
CLASP			Mutable object returned
The CERT Oracle Secure Coding Standard for Java (2011)	OBJ04-J		Provide mutable classes with copy functionality to safely allow passing instances to untrusted code
The CERT Oracle Secure Coding Standard for Java (2011)	OBJ05-J		Defensively copy private mutable class members before returning their references
SEI CERT Perl Coding Standard	EXP34-PL	Imprecise	Do not modify $_ in list or sorting functions
Software Fault Patterns	SFP23		Exposed Data

References

[REF-18] Secure Software, Inc.. "The CLASP Application Security Process". 2005. <https://cwe.mitre.org/documents/sources/TheCLASPApplicationSecurityProcess.pdf>.

Content History

Submissions
Submission Date	Submitter	Organization
2006-07-19 (CWE Draft 3, 2006-07-19)	CLASP
2006-07-19 (CWE Draft 3, 2006-07-19)
Modifications
Modification Date	Modifier	Organization
2008-07-01	Eric Dalci	Cigital
2008-07-01	updated Time_of_Introduction
2008-09-08	CWE Content Team	MITRE
2008-09-08	updated Applicable_Platforms, Common_Consequences, Relationships, Other_Notes, Taxonomy_Mappings
2010-09-27	CWE Content Team	MITRE
2010-09-27	updated Name, Taxonomy_Mappings
2011-06-01	CWE Content Team	MITRE
2011-06-01	updated Common_Consequences, Relationships, Taxonomy_Mappings
2012-05-11	CWE Content Team	MITRE
2012-05-11	updated Relationships, Taxonomy_Mappings
2012-10-30	CWE Content Team	MITRE
2012-10-30	updated Demonstrative_Examples
2014-06-23	CWE Content Team	MITRE
2014-06-23	updated Description, Other_Notes, Potential_Mitigations
2014-07-30	CWE Content Team	MITRE
2014-07-30	updated Relationships, Taxonomy_Mappings
2017-11-08	CWE Content Team	MITRE
2017-11-08	updated Taxonomy_Mappings
2019-01-03	CWE Content Team	MITRE
2019-01-03	updated Relationships, Taxonomy_Mappings
2020-02-24	CWE Content Team	MITRE
2020-02-24	updated References
2021-03-15	CWE Content Team	MITRE
2021-03-15	updated Relationships
2023-04-27	CWE Content Team	MITRE
2023-04-27	updated Relationships
2023-06-29	CWE Content Team	MITRE
2023-06-29	updated Mapping_Notes
Previous Entry Names
Change Date	Previous Entry Name
2010-09-27	Passing Mutable Objects to an Untrusted Method

Weakness ID: 248

View customized information:

Description

An exception is thrown from a function, but it is not caught.

Extended Description

When an exception is not caught, it may cause the program to crash or expose sensitive information.

Relationships

Relevant to the view "Research Concepts" (CWE-1000)

Nature	Type	ID	Name
ChildOf	Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource.	755	Improper Handling of Exceptional Conditions
ChildOf	Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource.	705	Incorrect Control Flow Scoping
ParentOf	Variant - a weakness that is linked to a certain type of product, typically involving a specific language or technology. More specific than a Base weakness. Variant level weaknesses typically describe issues in terms of 3 to 5 of the following dimensions: behavior, property, technology, language, and resource.	600	Uncaught Exception in Servlet

Relevant to the view "Software Development" (CWE-699)

Nature	Type	ID	Name
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	389	Error Conditions, Return Values, Status Codes

Relevant to the view "CISQ Quality Measures (2020)" (CWE-1305)

Nature	Type	ID	Name
ChildOf	Pillar - a weakness that is the most abstract type of weakness and represents a theme for all class/base/variant weaknesses related to it. A Pillar is different from a Category as a Pillar is still technically a type of weakness that describes a mistake, while a Category represents a common characteristic used to group related things.	703	Improper Check or Handling of Exceptional Conditions

Relevant to the view "CISQ Data Protection Measures" (CWE-1340)

Nature	Type	ID	Name
ChildOf	Pillar - a weakness that is the most abstract type of weakness and represents a theme for all class/base/variant weaknesses related to it. A Pillar is different from a Category as a Pillar is still technically a type of weakness that describes a mistake, while a Category represents a common characteristic used to group related things.	703	Improper Check or Handling of Exceptional Conditions

Modes Of Introduction

Phase	Note
Implementation

Applicable Platforms

Languages

C++ (Undetermined Prevalence)

Java (Undetermined Prevalence)

C# (Undetermined Prevalence)

Common Consequences

Scope	Impact	Likelihood
Availability Confidentiality	Technical Impact: DoS: Crash, Exit, or Restart; Read Application Data An uncaught exception could cause the system to be placed in a state that could lead to a crash, exposure of sensitive information or other unintended behaviors.

Demonstrative Examples

Example 1

The following example attempts to resolve a hostname.

(bad code)

Example Language: Java

protected void doPost (HttpServletRequest req, HttpServletResponse res) throws IOException {

String ip = req.getRemoteAddr();
InetAddress addr = InetAddress.getByName(ip);
...
out.println("hello " + addr.getHostName());

}

A DNS lookup failure will cause the Servlet to throw an exception.

Example 2

The _alloca() function allocates memory on the stack. If an allocation request is too large for the available stack space, _alloca() throws an exception. If the exception is not caught, the program will crash, potentially enabling a denial of service attack. _alloca() has been deprecated as of Microsoft Visual Studio 2005(R). It has been replaced with the more secure _alloca_s().

Example 3

EnterCriticalSection() can raise an exception, potentially causing the program to crash. Under operating systems prior to Windows 2000, the EnterCriticalSection() function can raise an exception in low memory situations. If the exception is not caught, the program will crash, potentially enabling a denial of service attack.

Observed Examples

Reference	Description
CVE-2023-41151	SDK for OPC Unified Architecture (OPC UA) server has uncaught exception when a socket is blocked for writing but the server tries to send an error
CVE-2023-21087	Java code in a smartphone OS can encounter a "boot loop" due to an uncaught exception

Detection Methods

Automated Static Analysis

Effectiveness: High

Memberships

Nature	Type	ID	Name
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	227	7PK - API Abuse
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	730	OWASP Top Ten 2004 Category A9 - Denial of Service
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	851	The CERT Oracle Secure Coding Standard for Java (2011) Chapter 8 - Exceptional Behavior (ERR)
MemberOf	View - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries).	884	CWE Cross-section
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	962	SFP Secondary Cluster: Unchecked Status Condition
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1141	SEI CERT Oracle Secure Coding Standard for Java - Guidelines 07. Exceptional Behavior (ERR)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1181	SEI CERT Perl Coding Standard - Guidelines 03. Expressions (EXP)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1410	Comprehensive Categorization: Insufficient Control Flow Management

Vulnerability Mapping Notes

Usage: ALLOWED

(this CWE ID could be used to map to real-world vulnerabilities)

Reason: Acceptable-Use

Rationale:

This CWE entry is at the Base level of abstraction, which is a preferred level of abstraction for mapping to the root causes of vulnerabilities.

Comments:

Taxonomy Mappings

Mapped Taxonomy Name	Node ID	Fit	Mapped Node Name
7 Pernicious Kingdoms			Often Misused: Exception Handling
The CERT Oracle Secure Coding Standard for Java (2011)	ERR05-J		Do not let checked exceptions escape from a finally block
The CERT Oracle Secure Coding Standard for Java (2011)	ERR06-J		Do not throw undeclared checked exceptions
SEI CERT Perl Coding Standard	EXP31-PL	Exact	Do not suppress or ignore exceptions
Software Fault Patterns	SFP4		Unchecked Status Condition

References

Content History

Submissions
Submission Date	Submitter	Organization
2006-07-19 (CWE Draft 3, 2006-07-19)	7 Pernicious Kingdoms
2006-07-19 (CWE Draft 3, 2006-07-19)
Modifications
Modification Date	Modifier	Organization
2008-07-01	Eric Dalci	Cigital
2008-07-01	updated Time_of_Introduction
2008-08-15		Veracode
2008-08-15	Suggested OWASP Top Ten 2004 mapping
2008-09-08	CWE Content Team	MITRE
2008-09-08	updated Applicable_Platforms, Relationships, Taxonomy_Mappings
2008-09-24	CWE Content Team	MITRE
2008-09-24	Removed C from Applicable_Platforms
2008-10-14	CWE Content Team	MITRE
2008-10-14	updated Applicable_Platforms
2009-03-10	CWE Content Team	MITRE
2009-03-10	updated Relationships
2011-03-29	CWE Content Team	MITRE
2011-03-29	updated Description, Relationships
2011-06-01	CWE Content Team	MITRE
2011-06-01	updated Common_Consequences, Relationships, Taxonomy_Mappings
2012-05-11	CWE Content Team	MITRE
2012-05-11	updated Common_Consequences, Demonstrative_Examples, Relationships, Taxonomy_Mappings
2014-07-30	CWE Content Team	MITRE
2014-07-30	updated Demonstrative_Examples, Relationships, Taxonomy_Mappings
2017-11-08	CWE Content Team	MITRE
2017-11-08	updated Relationships, Taxonomy_Mappings
2019-01-03	CWE Content Team	MITRE
2019-01-03	updated Relationships, Taxonomy_Mappings
2019-06-20	CWE Content Team	MITRE
2019-06-20	updated Related_Attack_Patterns
2020-02-24	CWE Content Team	MITRE
2020-02-24	updated References
2020-08-20	CWE Content Team	MITRE
2020-08-20	updated Relationships
2020-12-10	CWE Content Team	MITRE
2020-12-10	updated Relationships
2021-03-15	CWE Content Team	MITRE
2021-03-15	updated Relationships
2023-04-27	CWE Content Team	MITRE
2023-04-27	updated Detection_Factors, Relationships
2023-06-29	CWE Content Team	MITRE
2023-06-29	updated Mapping_Notes, Relationships
2024-02-29 (CWE 4.14, 2024-02-29)	CWE Content Team	MITRE
2024-02-29 (CWE 4.14, 2024-02-29)	updated Observed_Examples
Previous Entry Names
Change Date	Previous Entry Name
2008-01-30	Often Misused: Exception Handling

Weakness ID: 391

Vulnerability Mapping: PROHIBITEDThis CWE ID must not be used to map to real-world vulnerabilities
Abstraction: BaseBase - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.

View customized information:

Description

Relationships

Relevant to the view "Research Concepts" (CWE-1000)

Nature	Type	ID	Name
ChildOf	Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource.	754	Improper Check for Unusual or Exceptional Conditions

Relevant to the view "Software Development" (CWE-699)

Nature	Type	ID	Name
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	389	Error Conditions, Return Values, Status Codes

Relevant to the view "Architectural Concepts" (CWE-1008)

Nature	Type	ID	Name
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1020	Verify Message Integrity

Relevant to the view "CISQ Quality Measures (2020)" (CWE-1305)

Nature	Type	ID	Name
ChildOf	Pillar - a weakness that is the most abstract type of weakness and represents a theme for all class/base/variant weaknesses related to it. A Pillar is different from a Category as a Pillar is still technically a type of weakness that describes a mistake, while a Category represents a common characteristic used to group related things.	703	Improper Check or Handling of Exceptional Conditions

Relevant to the view "CISQ Data Protection Measures" (CWE-1340)

Nature	Type	ID	Name
ChildOf	Pillar - a weakness that is the most abstract type of weakness and represents a theme for all class/base/variant weaknesses related to it. A Pillar is different from a Category as a Pillar is still technically a type of weakness that describes a mistake, while a Category represents a common characteristic used to group related things.	703	Improper Check or Handling of Exceptional Conditions

Modes Of Introduction

Phase	Note
Implementation	REALIZATION: This weakness is caused during implementation of an architectural security tactic.

Applicable Platforms

Languages

Class: Not Language-Specific (Undetermined Prevalence)

Common Consequences

Scope	Impact	Likelihood
Integrity Other	Technical Impact: Varies by Context; Unexpected State; Alter Execution Logic

Likelihood Of Exploit

Medium

Demonstrative Examples

Example 1

The following code excerpt ignores a rarely-thrown exception from doExchange().

(bad code)

Example Language: Java

try {

doExchange();

}
catch (RareException e) {

// this can never happen

}

If a RareException were to ever be thrown, the program would continue to execute as though nothing unusual had occurred. The program records no evidence indicating the special situation, potentially frustrating any later attempt to explain the program's behavior.

Potential Mitigations

Phase: Requirements

The choice between a language which has named or unnamed exceptions needs to be done. While unnamed exceptions exacerbate the chance of not properly dealing with an exception, named exceptions suffer from the up call version of the weak base class problem.

Phase: Requirements

A language can be used which requires, at compile time, to catch all serious exceptions. However, one must make sure to use the most current version of the API as new exceptions could be added.

Phase: Implementation

Catch all relevant exceptions. This is the recommended solution. Ensure that all exceptions are handled in such a way that you can be sure of the state of your system at any given moment.

Detection Methods

Automated Static Analysis

Effectiveness: High

Memberships

Nature	Type	ID	Name
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	388	7PK - Errors
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	728	OWASP Top Ten 2004 Category A7 - Improper Error Handling
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	743	CERT C Secure Coding Standard (2008) Chapter 10 - Input Output (FIO)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	746	CERT C Secure Coding Standard (2008) Chapter 13 - Error Handling (ERR)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	876	CERT C++ Secure Coding Section 08 - Memory Management (MEM)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	877	CERT C++ Secure Coding Section 09 - Input Output (FIO)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	880	CERT C++ Secure Coding Section 12 - Exceptions and Error Handling (ERR)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	962	SFP Secondary Cluster: Unchecked Status Condition
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1159	SEI CERT C Coding Standard - Guidelines 05. Floating Point (FLP)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1167	SEI CERT C Coding Standard - Guidelines 12. Error Handling (ERR)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1171	SEI CERT C Coding Standard - Guidelines 50. POSIX (POS)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1181	SEI CERT Perl Coding Standard - Guidelines 03. Expressions (EXP)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1405	Comprehensive Categorization: Improper Check or Handling of Exceptional Conditions

Vulnerability Mapping Notes

Usage: PROHIBITED

(this CWE ID must not be used to map to real-world vulnerabilities)

Reasons: Potential Deprecation, Frequent Misuse, Frequent Misinterpretation

Rationale:

This entry is slated for deprecation; it has multiple widespread interpretations by CWE analysts. It combines information from three different taxonomies, but each taxonomy is talking about a slightly different issue.

Comments:

Consider CWE-252, CWE-1069, CWE-248, or other entries under CWE-754: Improper Check for Unusual or Exceptional Conditions or CWE-755: Improper Handling of Exceptional Conditions.

Suggestions:

CWE-ID	Comment
CWE-252	Unchecked Return Value
CWE-1069	Empty Exception Block
CWE-248	Uncaught Exception

Notes

Other

When a programmer ignores an exception, they implicitly state that they are operating under one of two assumptions:

This method call can never fail.
It doesn't matter if this call fails.

Maintenance

This entry is slated for deprecation; it has multiple widespread interpretations by CWE analysts. It currently combines information from three different taxonomies, but each taxonomy is talking about a slightly different issue. CWE analysts might map to this entry based on any of these issues. 7PK has "Empty Catch Block" which has an association with empty exception block (CWE-1069); in this case, the exception has performed the check, but does not handle. In PLOVER there is "Unchecked Return Value" which is CWE-252, but unlike "Empty Catch Block" there isn't even a check of the issue - and "Unchecked Error Condition" implies lack of a check. For CLASP, "Uncaught Exception" (CWE-248) is associated with incorrect error propagation - uncovered in CWE 3.2 and earlier, at least. There are other issues related to error handling and checks.

Taxonomy Mappings

Mapped Taxonomy Name	Node ID	Fit	Mapped Node Name
PLOVER			Unchecked Return Value
7 Pernicious Kingdoms			Empty Catch Block
CLASP			Uncaught exception
OWASP Top Ten 2004	A7	CWE More Specific	Improper Error Handling
CERT C Secure Coding	ERR00-C		Adopt and implement a consistent and comprehensive error-handling policy
CERT C Secure Coding	ERR33-C	CWE More Abstract	Detect and handle standard library errors
CERT C Secure Coding	ERR34-C	CWE More Abstract	Detect errors when converting a string to a number
CERT C Secure Coding	FLP32-C	Imprecise	Prevent or detect domain and range errors in math functions
CERT C Secure Coding	POS54-C	CWE More Abstract	Detect and handle POSIX library errors
SEI CERT Perl Coding Standard	EXP31-PL	Imprecise	Do not suppress or ignore exceptions
Software Fault Patterns	SFP4		Unchecked Status Condition

References

[REF-18] Secure Software, Inc.. "The CLASP Application Security Process". 2005. <https://cwe.mitre.org/documents/sources/TheCLASPApplicationSecurityProcess.pdf>.

Content History

Submissions
Submission Date	Submitter	Organization
2006-07-19 (CWE Draft 3, 2006-07-19)	PLOVER
2006-07-19 (CWE Draft 3, 2006-07-19)
Modifications
Modification Date	Modifier	Organization
2008-07-01	Eric Dalci	Cigital
2008-07-01	updated Time_of_Introduction
2008-08-01		KDM Analytics
2008-08-01	added/updated white box definitions
2008-08-15		Veracode
2008-08-15	Suggested OWASP Top Ten 2004 mapping
2008-09-08	CWE Content Team	MITRE
2008-09-08	updated Maintenance_Notes, Relationships, Other_Notes, Taxonomy_Mappings
2008-11-24	CWE Content Team	MITRE
2008-11-24	updated Relationships, Taxonomy_Mappings
2009-05-27	CWE Content Team	MITRE
2009-05-27	updated Demonstrative_Examples
2009-07-17	KDM Analytics
2009-07-17	Improved the White_Box_Definition
2009-07-27	CWE Content Team	MITRE
2009-07-27	updated White_Box_Definitions
2011-06-01	CWE Content Team	MITRE
2011-06-01	updated Common_Consequences
2011-06-27	CWE Content Team	MITRE
2011-06-27	updated Common_Consequences
2011-09-13	CWE Content Team	MITRE
2011-09-13	updated Relationships, Taxonomy_Mappings
2012-05-11	CWE Content Team	MITRE
2012-05-11	updated Relationships
2012-10-30	CWE Content Team	MITRE
2012-10-30	updated Potential_Mitigations
2014-06-23	CWE Content Team	MITRE
2014-06-23	updated Other_Notes
2014-07-30	CWE Content Team	MITRE
2014-07-30	updated Relationships, Taxonomy_Mappings
2017-11-08	CWE Content Team	MITRE
2017-11-08	updated Applicable_Platforms, Modes_of_Introduction, Relationships, Taxonomy_Mappings, White_Box_Definitions
2019-01-03	CWE Content Team	MITRE
2019-01-03	updated Relationships, Taxonomy_Mappings
2019-06-20	CWE Content Team	MITRE
2019-06-20	updated Description, Maintenance_Notes
2020-02-24	CWE Content Team	MITRE
2020-02-24	updated References
2020-08-20	CWE Content Team	MITRE
2020-08-20	updated Relationships
2020-12-10	CWE Content Team	MITRE
2020-12-10	updated Relationships
2021-03-15	CWE Content Team	MITRE
2021-03-15	updated Description, Relationships
2021-07-20	CWE Content Team	MITRE
2021-07-20	updated Relationships
2023-04-27	CWE Content Team	MITRE
2023-04-27	updated Detection_Factors, Relationships, Time_of_Introduction
2023-06-29	CWE Content Team	MITRE
2023-06-29	updated Mapping_Notes
2024-02-29 (CWE 4.14, 2024-02-29)	CWE Content Team	MITRE
2024-02-29 (CWE 4.14, 2024-02-29)	updated Mapping_Notes

Weakness ID: 252

View customized information:

Description

The product does not check the return value from a method or function, which can prevent it from detecting unexpected states and conditions.

Extended Description

Two common programmer assumptions are "this function call can never fail" and "it doesn't matter if this function call fails". If an attacker can force the function to fail or otherwise return a value that is not expected, then the subsequent program logic could lead to a vulnerability, because the product is not in a state that the programmer assumes. For example, if the program calls a function to drop privileges but does not check the return code to ensure that privileges were successfully dropped, then the program will continue to operate with the higher privileges.

Relationships

Relevant to the view "Research Concepts" (CWE-1000)

Nature	Type	ID	Name
ChildOf	Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource.	754	Improper Check for Unusual or Exceptional Conditions
ParentOf	Chain - a Compound Element that is a sequence of two or more separate weaknesses that can be closely linked together within software. One weakness, X, can directly create the conditions that are necessary to cause another weakness, Y, to enter a vulnerable condition. When this happens, CWE refers to X as "primary" to Y, and Y is "resultant" from X. Chains can involve more than two weaknesses, and in some cases, they might have a tree-like structure.	690	Unchecked Return Value to NULL Pointer Dereference
PeerOf	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	273	Improper Check for Dropped Privileges
CanPrecede	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	476	NULL Pointer Dereference

Relevant to the view "Software Development" (CWE-699)

Nature	Type	ID	Name
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	389	Error Conditions, Return Values, Status Codes

Relevant to the view "Weaknesses for Simplified Mapping of Published Vulnerabilities" (CWE-1003)

Nature	Type	ID	Name
ChildOf	Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource.	754	Improper Check for Unusual or Exceptional Conditions

Background Details

Many functions will return some value about the success of their actions. This will alert the program whether or not to handle any errors caused by that function.

Modes Of Introduction

Phase	Note
Implementation

Applicable Platforms

Languages

Class: Not Language-Specific (Undetermined Prevalence)

Common Consequences

Scope	Impact	Likelihood
Availability Integrity	Technical Impact: Unexpected State; DoS: Crash, Exit, or Restart An unexpected return value could place the system in a state that could lead to a crash or other unintended behaviors.

Likelihood Of Exploit

Low

Demonstrative Examples

Example 1

Consider the following code segment:

(bad code)

Example Language: C

char buf[10], cp_buf[10];
fgets(buf, 10, stdin);
strcpy(cp_buf, buf);

Example 2

In the following example, it is possible to request that memcpy move a much larger segment of memory than assumed:

(bad code)

Example Language: C

int returnChunkSize(void *) {

/* if chunk info is valid, return the size of usable memory,

* else, return -1 to indicate an error

*/
...

}
int main() {

...
memcpy(destBuf, srcBuf, (returnChunkSize(destBuf)-1));
...

}

If returnChunkSize() happens to encounter an error it will return -1. Notice that the return value is not checked before the memcpy operation (CWE-252), so -1 can be passed as the size argument to memcpy() (CWE-805). Because memcpy() assumes that the value is unsigned, it will be interpreted as MAXINT-1 (CWE-195), and therefore will copy far more memory than is likely available to the destination buffer (CWE-787, CWE-788).

Example 3

The following code does not check to see if memory allocation succeeded before attempting to use the pointer returned by malloc().

(bad code)

Example Language: C

buf = (char*) malloc(req_size);
strncpy(buf, xfer, req_size);

The traditional defense of this coding error is: "If my program runs out of memory, it will fail. It doesn't matter whether I handle the error or allow the program to die with a segmentation fault when it tries to dereference the null pointer." This argument ignores three important considerations:

Depending upon the type and size of the application, it may be possible to free memory that is being used elsewhere so that execution can continue.
It is impossible for the program to perform a graceful exit if required. If the program is performing an atomic operation, it can leave the system in an inconsistent state.
The programmer has lost the opportunity to record diagnostic information. Did the call to malloc() fail because req_size was too large or because there were too many requests being handled at the same time? Or was it caused by a memory leak that has built up over time? Without handling the error, there is no way to know.

Example 4

The following examples read a file into a byte array.

(bad code)

Example Language: C#

char[] byteArray = new char[1024];
for (IEnumerator i=users.GetEnumerator(); i.MoveNext() ;i.Current()) {

}

(bad code)

Example Language: Java

FileInputStream fis;
byte[] byteArray = new byte[1024];
for (Iterator i=users.iterator(); i.hasNext();) {

Example 5

The following code does not check to see if the string returned by getParameter() is null before calling the member function compareTo(), potentially causing a NULL dereference.

(bad code)

Example Language: Java

String itemName = request.getParameter(ITEM_NAME);
if (itemName.compareTo(IMPORTANT_ITEM) == 0) {

...

}
...

The following code does not check to see if the string returned by the Item property is null before calling the member function Equals(), potentially causing a NULL dereference.

(bad code)

Example Language: Java

String itemName = request.Item(ITEM_NAME);
if (itemName.Equals(IMPORTANT_ITEM)) {

...

}
...

The traditional defense of this coding error is: "I know the requested value will always exist because.... If it does not exist, the program cannot perform the desired behavior so it doesn't matter whether I handle the error or allow the program to die dereferencing a null value." But attackers are skilled at finding unexpected paths through programs, particularly when exceptions are involved.

Example 6

The following code shows a system property that is set to null and later dereferenced by a programmer who mistakenly assumes it will always be defined.

(bad code)

Example Language: Java

System.clearProperty("os.name");
...
String os = System.getProperty("os.name");
if (os.equalsIgnoreCase("Windows 95")) System.out.println("Not supported");

The traditional defense of this coding error is: "I know the requested value will always exist because.... If it does not exist, the program cannot perform the desired behavior so it doesn't matter whether I handle the error or allow the program to die dereferencing a null value." But attackers are skilled at finding unexpected paths through programs, particularly when exceptions are involved.

Example 7

The following VB.NET code does not check to make sure that it has read 50 bytes from myfile.txt. This can cause DoDangerousOperation() to operate on an unexpected value.

(bad code)

Example Language: C#

Dim MyFile As New FileStream("myfile.txt", FileMode.Open, FileAccess.Read, FileShare.Read)
Dim MyArray(50) As Byte
MyFile.Read(MyArray, 0, 50)
DoDangerousOperation(MyArray(20))

Example 8

It is not uncommon for Java programmers to misunderstand read() and related methods that are part of many java.io classes. Most errors and unusual events in Java result in an exception being thrown. But the stream and reader classes do not consider it unusual or exceptional if only a small amount of data becomes available. These classes simply add the small amount of data to the return buffer, and set the return value to the number of bytes or characters read. There is no guarantee that the amount of data returned is equal to the amount of data requested. This behavior makes it important for programmers to examine the return value from read() and other IO methods to ensure that they receive the amount of data they expect.

Example 9

This example takes an IP address from a user, verifies that it is well formed and then looks up the hostname and copies it into a buffer.

(bad code)

Example Language: C

void host_lookup(char *user_supplied_addr){

}

Note that this code is also vulnerable to a buffer overflow (CWE-119).

Example 10

The following function attempts to acquire a lock in order to perform operations on a shared resource.

(bad code)

Example Language: C

void f(pthread_mutex_t *mutex) {

pthread_mutex_lock(mutex);

/* access shared resource */

pthread_mutex_unlock(mutex);

}

However, the code does not check the value returned by pthread_mutex_lock() for errors. If pthread_mutex_lock() cannot acquire the mutex for any reason, the function may introduce a race condition into the program and result in undefined behavior.

In order to avoid data races, correctly written programs must check the result of thread synchronization functions and appropriately handle all errors, either by attempting to recover from them or reporting them to higher levels.

(good code)

Example Language: C

int f(pthread_mutex_t *mutex) {

int result;

result = pthread_mutex_lock(mutex);
if (0 != result)

return result;

/* access shared resource */

return pthread_mutex_unlock(mutex);

}

Observed Examples

Reference	Description
CVE-2020-17533	Chain: unchecked return value (CWE-252) of some functions for policy enforcement leads to authorization bypass (CWE-862)
CVE-2020-6078	Chain: The return value of a function returning a pointer is not checked for success (CWE-252) resulting in the later use of an uninitialized variable (CWE-456) and a null pointer dereference (CWE-476)
CVE-2019-15900	Chain: sscanf() call is used to check if a username and group exists, but the return value of sscanf() call is not checked (CWE-252), causing an uninitialized variable to be checked (CWE-457), returning success to allow authorization bypass for executing a privileged (CWE-863).
CVE-2007-3798	Unchecked return value leads to resultant integer overflow and code execution.
CVE-2006-4447	Program does not check return value when invoking functions to drop privileges, which could leave users with higher privileges than expected by forcing those functions to fail.
CVE-2006-2916	Program does not check return value when invoking functions to drop privileges, which could leave users with higher privileges than expected by forcing those functions to fail.
CVE-2008-5183	chain: unchecked return value can lead to NULL dereference
CVE-2010-0211	chain: unchecked return value (CWE-252) leads to free of invalid, uninitialized pointer (CWE-824).
CVE-2017-6964	Linux-based device mapper encryption program does not check the return value of setuid and setgid allowing attackers to execute code with unintended privileges.
CVE-2002-1372	Chain: Return values of file/socket operations are not checked (CWE-252), allowing resultant consumption of file descriptors (CWE-772).

Potential Mitigations

Phase: Implementation

Check the results of all functions that return a value and verify that the value is expected.

Effectiveness: High

Note: Checking the return value of the function will typically be sufficient, however beware of race conditions (CWE-362) in a concurrent environment.

Phase: Implementation

Ensure that you account for all possible return values from the function.

Phase: Implementation

When designing a function, make sure you return a value or throw an exception in case of an error.

Weakness Ordinalities

Ordinality	Description
Primary	(where the weakness exists independent of other weaknesses)

Detection Methods

Automated Static Analysis

Effectiveness: High

Memberships

Nature	Type	ID	Name
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	227	7PK - API Abuse
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	728	OWASP Top Ten 2004 Category A7 - Improper Error Handling
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	742	CERT C Secure Coding Standard (2008) Chapter 9 - Memory Management (MEM)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	847	The CERT Oracle Secure Coding Standard for Java (2011) Chapter 4 - Expressions (EXP)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	876	CERT C++ Secure Coding Section 08 - Memory Management (MEM)
MemberOf	View - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries).	884	CWE Cross-section
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	962	SFP Secondary Cluster: Unchecked Status Condition
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1129	CISQ Quality Measures (2016) - Reliability
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1131	CISQ Quality Measures (2016) - Security
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1136	SEI CERT Oracle Secure Coding Standard for Java - Guidelines 02. Expressions (EXP)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1167	SEI CERT C Coding Standard - Guidelines 12. Error Handling (ERR)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1171	SEI CERT C Coding Standard - Guidelines 50. POSIX (POS)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1181	SEI CERT Perl Coding Standard - Guidelines 03. Expressions (EXP)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1306	CISQ Quality Measures - Reliability
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1308	CISQ Quality Measures - Security
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1405	Comprehensive Categorization: Improper Check or Handling of Exceptional Conditions

Vulnerability Mapping Notes

Usage: ALLOWED

(this CWE ID could be used to map to real-world vulnerabilities)

Reason: Acceptable-Use

Rationale:

This CWE entry is at the Base level of abstraction, which is a preferred level of abstraction for mapping to the root causes of vulnerabilities.

Comments:

Taxonomy Mappings

Mapped Taxonomy Name	Node ID	Fit	Mapped Node Name
7 Pernicious Kingdoms			Unchecked Return Value
CLASP			Ignored function return value
OWASP Top Ten 2004	A7	CWE More Specific	Improper Error Handling
CERT C Secure Coding	ERR33-C	Imprecise	Detect and handle standard library errors
CERT C Secure Coding	POS54-C	Imprecise	Detect and handle POSIX library errors
The CERT Oracle Secure Coding Standard for Java (2011)	EXP00-J		Do not ignore values returned by methods
SEI CERT Perl Coding Standard	EXP32-PL	Exact	Do not ignore function return values
Software Fault Patterns	SFP4		Unchecked Status Condition
OMG ASCSM	ASCSM-CWE-252-resource
OMG ASCRM	ASCRM-CWE-252-data
OMG ASCRM	ASCRM-CWE-252-resource

References

[REF-62] Mark Dowd, John McDonald and Justin Schuh. "The Art of Software Security Assessment". Chapter 7, "Program Building Blocks" Page 341. 1st Edition. Addison Wesley. 2006.

[REF-7] Michael Howard and David LeBlanc. "Writing Secure Code". Chapter 20, "Checking Returns" Page 624. 2nd Edition. Microsoft Press. 2002-12-04. <https://www.microsoftpressstore.com/store/writing-secure-code-9780735617223>.

[REF-44] Michael Howard, David LeBlanc and John Viega. "24 Deadly Sins of Software Security". "Sin 11: Failure to Handle Errors Correctly." Page 183. McGraw-Hill. 2010.

[REF-961] Object Management Group (OMG). "Automated Source Code Reliability Measure (ASCRM)". ASCRM-CWE-252-data. 2016-01. <http://www.omg.org/spec/ASCRM/1.0/>.

[REF-961] Object Management Group (OMG). "Automated Source Code Reliability Measure (ASCRM)". ASCRM-CWE-252-resource. 2016-01. <http://www.omg.org/spec/ASCRM/1.0/>.

[REF-962] Object Management Group (OMG). "Automated Source Code Security Measure (ASCSM)". ASCSM-CWE-252-resource. 2016-01. <http://www.omg.org/spec/ASCSM/1.0/>.

Content History

Submissions
Submission Date	Submitter	Organization
2006-07-19 (CWE Draft 3, 2006-07-19)	7 Pernicious Kingdoms
2006-07-19 (CWE Draft 3, 2006-07-19)
Contributions
Contribution Date	Contributor	Organization
2010-04-30	Martin Sebor	Cisco Systems, Inc.
2010-04-30	Provided Demonstrative Example and suggested CERT reference
Modifications
Modification Date	Modifier	Organization
2008-09-08	CWE Content Team	MITRE
2008-09-08	updated Common_Consequences, Relationships, Other_Notes, Taxonomy_Mappings
2008-11-24	CWE Content Team	MITRE
2008-11-24	updated Relationships, Taxonomy_Mappings
2009-01-12	CWE Content Team	MITRE
2009-01-12	updated Background_Details, Demonstrative_Examples, Description, Observed_Examples, Other_Notes, Potential_Mitigations
2009-03-10	CWE Content Team	MITRE
2009-03-10	updated Relationships
2009-05-27	CWE Content Team	MITRE
2009-05-27	updated Demonstrative_Examples
2009-07-27	CWE Content Team	MITRE
2009-07-27	updated Demonstrative_Examples
2009-12-28	CWE Content Team	MITRE
2009-12-28	updated Common_Consequences, Demonstrative_Examples, References
2010-02-16	CWE Content Team	MITRE
2010-02-16	updated Demonstrative_Examples, Potential_Mitigations, References
2010-04-05	CWE Content Team	MITRE
2010-04-05	updated Demonstrative_Examples
2010-06-21	CWE Content Team	MITRE
2010-06-21	updated Demonstrative_Examples, References
2010-09-27	CWE Content Team	MITRE
2010-09-27	updated Observed_Examples
2010-12-13	CWE Content Team	MITRE
2010-12-13	updated Demonstrative_Examples
2011-06-01	CWE Content Team	MITRE
2011-06-01	updated Common_Consequences, Demonstrative_Examples, Relationships, Taxonomy_Mappings
2011-06-27	CWE Content Team	MITRE
2011-06-27	updated Common_Consequences
2011-09-13	CWE Content Team	MITRE
2011-09-13	updated Relationships, Taxonomy_Mappings
2012-05-11	CWE Content Team	MITRE
2012-05-11	updated Common_Consequences, References, Relationships
2014-06-23	CWE Content Team	MITRE
2014-06-23	updated Demonstrative_Examples, Potential_Mitigations
2014-07-30	CWE Content Team	MITRE
2014-07-30	updated Demonstrative_Examples, Relationships, Taxonomy_Mappings
2017-11-08	CWE Content Team	MITRE
2017-11-08	updated Applicable_Platforms, References, Relationships, Taxonomy_Mappings
2018-03-27	CWE Content Team	MITRE
2018-03-27	updated References
2019-01-03	CWE Content Team	MITRE
2019-01-03	updated References, Relationships, Taxonomy_Mappings
2019-06-20	CWE Content Team	MITRE
2019-06-20	updated Relationships
2020-02-24	CWE Content Team	MITRE
2020-02-24	updated References
2020-06-25	CWE Content Team	MITRE
2020-06-25	updated Observed_Examples
2020-08-20	CWE Content Team	MITRE
2020-08-20	updated Relationships
2021-03-15	CWE Content Team	MITRE
2021-03-15	updated Demonstrative_Examples, Observed_Examples, Relationships, Weakness_Ordinalities
2021-07-20	CWE Content Team	MITRE
2021-07-20	updated Observed_Examples
2023-01-31	CWE Content Team	MITRE
2023-01-31	updated Description
2023-04-27	CWE Content Team	MITRE
2023-04-27	updated Detection_Factors, Relationships
2023-06-29	CWE Content Team	MITRE
2023-06-29	updated Mapping_Notes, Relationships
2023-10-26	CWE Content Team	MITRE
2023-10-26	updated Observed_Examples

Weakness ID: 690 (Structure: Chain)Chain - a Compound Element that is a sequence of two or more separate weaknesses that can be closely linked together within software. One weakness, X, can directly create the conditions that are necessary to cause another weakness, Y, to enter a vulnerable condition. When this happens, CWE refers to X as "primary" to Y, and Y is "resultant" from X. Chains can involve more than two weaknesses, and in some cases, they might have a tree-like structure.

Vulnerability Mapping: DISCOURAGEDThis CWE ID should not be used to map to real-world vulnerabilities

View customized information:

Description

The product does not check for an error after calling a function that can return with a NULL pointer if the function fails, which leads to a resultant NULL pointer dereference.

Chain Components

Nature	Type	ID	Name
StartsWith	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	252	Unchecked Return Value
FollowedBy	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	476	NULL Pointer Dereference

Extended Description

While unchecked return value weaknesses are not limited to returns of NULL pointers (see the examples in CWE-252), functions often return NULL to indicate an error status. When this error condition is not checked, a NULL pointer dereference can occur.

Relationships

Relevant to the view "Research Concepts" (CWE-1000)

Nature	Type	ID	Name
ChildOf	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	252	Unchecked Return Value

Modes Of Introduction

Phase

Note

Implementation

A typical occurrence of this weakness occurs when an application includes user-controlled input to a malloc() call. The related code might be correct with respect to preventing buffer overflows, but if a large value is provided, the malloc() will fail due to insufficient memory. This problem also frequently occurs when a parsing routine expects that certain elements will always be present. If malformed input is provided, the parser might return NULL. For example, strtok() can return NULL.

Applicable Platforms

Languages

C (Undetermined Prevalence)

C++ (Undetermined Prevalence)

Common Consequences

Scope	Impact	Likelihood
Availability	Technical Impact: DoS: Crash, Exit, or Restart
Integrity Confidentiality Availability	Technical Impact: Execute Unauthorized Code or Commands; Read Memory; Modify Memory In rare circumstances, when NULL is equivalent to the 0x0 memory address and privileged code can access it, then writing or reading memory is possible, which may lead to code execution.

Demonstrative Examples

Example 1

The code below makes a call to the getUserName() function but doesn't check the return value before dereferencing (which may cause a NullPointerException).

(bad code)

Example Language: Java

String username = getUserName();
if (username.equals(ADMIN_USER)) {

...

}

Example 2

This example takes an IP address from a user, verifies that it is well formed and then looks up the hostname and copies it into a buffer.

(bad code)

Example Language: C

void host_lookup(char *user_supplied_addr){

}

Note that this code is also vulnerable to a buffer overflow (CWE-119).

Observed Examples

Reference	Description
CVE-2008-1052	Large Content-Length value leads to NULL pointer dereference when malloc fails.
CVE-2006-6227	Large message length field leads to NULL pointer dereference when malloc fails.
CVE-2006-2555	Parsing routine encounters NULL dereference when input is missing a colon separator.
CVE-2003-1054	URI parsing API sets argument to NULL when a parsing failure occurs, such as when the Referer header is missing a hostname, leading to NULL dereference.
CVE-2008-5183	chain: unchecked return value can lead to NULL dereference

Detection Methods

Black Box

This typically occurs in rarely-triggered error conditions, reducing the chances of detection during black box testing.

White Box

Code analysis can require knowledge of API behaviors for library functions that might return NULL, reducing the chances of detection when unknown libraries are used.

Memberships

Nature	Type	ID	Name
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	851	The CERT Oracle Secure Coding Standard for Java (2011) Chapter 8 - Exceptional Behavior (ERR)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	876	CERT C++ Secure Coding Section 08 - Memory Management (MEM)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1157	SEI CERT C Coding Standard - Guidelines 03. Expressions (EXP)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1181	SEI CERT Perl Coding Standard - Guidelines 03. Expressions (EXP)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1399	Comprehensive Categorization: Memory Safety

Vulnerability Mapping Notes

Usage: DISCOURAGED

(this CWE ID should not be used to map to real-world vulnerabilities)

Reason: Other

Rationale:

This CWE entry is a named chain, which combines multiple weaknesses.

Comments:

Mapping to each separate weakness in the chain would be more precise.

Taxonomy Mappings

Mapped Taxonomy Name	Node ID	Fit	Mapped Node Name
CERT C Secure Coding	EXP34-C	CWE More Specific	Do not dereference null pointers
The CERT Oracle Secure Coding Standard for Java (2011)	ERR08-J		Do not catch NullPointerException or any of its ancestors
SEI CERT Perl Coding Standard	EXP32-PL	CWE More Specific	Do not ignore function return values

Content History

Submissions
Submission Date	Submitter	Organization
2008-04-11 (CWE Draft 9, 2008-04-11)	CWE Content Team	MITRE
2008-04-11 (CWE Draft 9, 2008-04-11)
Modifications
Modification Date	Modifier	Organization
2008-07-01	Sean Eidemiller	Cigital
2008-07-01	added/updated demonstrative examples
2008-07-01	Eric Dalci	Cigital
2008-07-01	updated Time_of_Introduction
2008-09-08	CWE Content Team	MITRE
2008-09-08	updated Applicable_Platforms, Description, Detection_Factors, Relationships, Other_Notes
2009-12-28	CWE Content Team	MITRE
2009-12-28	updated Demonstrative_Examples
2010-09-27	CWE Content Team	MITRE
2010-09-27	updated Observed_Examples
2011-06-01	CWE Content Team	MITRE
2011-06-01	updated Common_Consequences, Relationships, Taxonomy_Mappings
2011-09-13	CWE Content Team	MITRE
2011-09-13	updated Relationships, Taxonomy_Mappings
2014-06-23	CWE Content Team	MITRE
2014-06-23	updated Modes_of_Introduction, Other_Notes
2017-01-19	CWE Content Team	MITRE
2017-01-19	updated Relationships
2017-11-08	CWE Content Team	MITRE
2017-11-08	updated Relationships, Relevant_Properties, Taxonomy_Mappings, Time_of_Introduction
2019-01-03	CWE Content Team	MITRE
2019-01-03	updated Relationships, Taxonomy_Mappings
2020-06-25	CWE Content Team	MITRE
2020-06-25	updated Common_Consequences
2021-03-15	CWE Content Team	MITRE
2021-03-15	updated Demonstrative_Examples, Relationships
2023-04-27	CWE Content Team	MITRE
2023-04-27	updated Relationships
2023-06-29	CWE Content Team	MITRE
2023-06-29	updated Mapping_Notes, Relationships

Weakness ID: 394

View customized information:

Description

The product does not properly check when a function or operation returns a value that is legitimate for the function, but is not expected by the product.

Relationships

Relevant to the view "Research Concepts" (CWE-1000)

Nature	Type	ID	Name
ChildOf	Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource.	754	Improper Check for Unusual or Exceptional Conditions

Relevant to the view "Software Development" (CWE-699)

Nature	Type	ID	Name
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	389	Error Conditions, Return Values, Status Codes

Modes Of Introduction

Phase	Note
Implementation

Applicable Platforms

Languages

Class: Not Language-Specific (Undetermined Prevalence)

Common Consequences

Scope	Impact	Likelihood
Integrity Other	Technical Impact: Unexpected State; Alter Execution Logic

Observed Examples

Reference	Description
CVE-2004-1395	Certain packets (zero byte and other lengths) cause a recvfrom call to produce an unexpected return code that causes a server's listening loop to exit.
CVE-2002-2124	Unchecked return code from recv() leads to infinite loop.
CVE-2005-2553	Kernel function does not properly handle when a null is returned by a function call, causing it to call another function that it shouldn't.
CVE-2005-1858	Memory not properly cleared when read() function call returns fewer bytes than expected.
CVE-2000-0536	Bypass access restrictions when connecting from IP whose DNS reverse lookup does not return a hostname.
CVE-2001-0910	Bypass access restrictions when connecting from IP whose DNS reverse lookup does not return a hostname.
CVE-2004-2371	Game server doesn't check return values for functions that handle text strings and associated size values.
CVE-2005-1267	Resultant infinite loop when function call returns -1 value.

Memberships

Nature	Type	ID	Name
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	728	OWASP Top Ten 2004 Category A7 - Improper Error Handling
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	962	SFP Secondary Cluster: Unchecked Status Condition
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1181	SEI CERT Perl Coding Standard - Guidelines 03. Expressions (EXP)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1306	CISQ Quality Measures - Reliability
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1405	Comprehensive Categorization: Improper Check or Handling of Exceptional Conditions

Vulnerability Mapping Notes

Usage: ALLOWED

(this CWE ID could be used to map to real-world vulnerabilities)

Reason: Acceptable-Use

Rationale:

This CWE entry is at the Base level of abstraction, which is a preferred level of abstraction for mapping to the root causes of vulnerabilities.

Comments:

Notes

Relationship

Usually primary, but can be resultant from issues such as behavioral change or API abuse. This can produce resultant vulnerabilities.

Taxonomy Mappings

Mapped Taxonomy Name	Node ID	Fit	Mapped Node Name
PLOVER			Unexpected Status Code or Return Value
Software Fault Patterns	SFP4		Unchecked Status Condition
SEI CERT Perl Coding Standard	EXP00-PL	Imprecise	Do not return undef

Content History

Submissions
Submission Date	Submitter	Organization
2006-07-19 (CWE Draft 3, 2006-07-19)	PLOVER
2006-07-19 (CWE Draft 3, 2006-07-19)
Modifications
Modification Date	Modifier	Organization
2008-07-01	Eric Dalci	Cigital
2008-07-01	updated Time_of_Introduction
2008-09-08	CWE Content Team	MITRE
2008-09-08	updated Relationships, Other_Notes, Taxonomy_Mappings
2009-03-10	CWE Content Team	MITRE
2009-03-10	updated Relationships
2009-12-28	CWE Content Team	MITRE
2009-12-28	updated Other_Notes, Relationship_Notes
2011-06-01	CWE Content Team	MITRE
2011-06-01	updated Common_Consequences
2011-06-27	CWE Content Team	MITRE
2011-06-27	updated Common_Consequences
2012-05-11	CWE Content Team	MITRE
2012-05-11	updated Relationships
2014-07-30	CWE Content Team	MITRE
2014-07-30	updated Relationships, Taxonomy_Mappings
2017-11-08	CWE Content Team	MITRE
2017-11-08	updated Applicable_Platforms, Taxonomy_Mappings
2019-01-03	CWE Content Team	MITRE
2019-01-03	updated Taxonomy_Mappings
2020-08-20	CWE Content Team	MITRE
2020-08-20	updated Relationships
2021-03-15	CWE Content Team	MITRE
2021-03-15	updated Relationships
2023-01-31	CWE Content Team	MITRE
2023-01-31	updated Description
2023-04-27	CWE Content Team	MITRE
2023-04-27	updated Relationships, Time_of_Introduction
2023-06-29	CWE Content Team	MITRE
2023-06-29	updated Mapping_Notes

Weakness ID: 134

View customized information:

Description

The product uses a function that accepts a format string as an argument, but the format string originates from an external source.

Extended Description

When an attacker can modify an externally-controlled format string, this can lead to buffer overflows, denial of service, or data representation problems.

It should be noted that in some circumstances, such as internationalization, the set of format strings is externally controlled by design. If the source of these format strings is trusted (e.g. only contained in library files that are only modifiable by the system administrator), then the external control might not itself pose a vulnerability.

Relationships

Relevant to the view "Research Concepts" (CWE-1000)

Nature	Type	ID	Name
ChildOf	Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource.	668	Exposure of Resource to Wrong Sphere
CanPrecede	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	123	Write-what-where Condition

Relevant to the view "Software Development" (CWE-699)

Nature	Type	ID	Name
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	133	String Errors

Relevant to the view "Weaknesses for Simplified Mapping of Published Vulnerabilities" (CWE-1003)

Nature	Type	ID	Name
ChildOf	Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource.	668	Exposure of Resource to Wrong Sphere

Relevant to the view "Seven Pernicious Kingdoms" (CWE-700)

Nature	Type	ID	Name
ChildOf	Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource.	20	Improper Input Validation

Modes Of Introduction

Phase	Note
Implementation	The programmer rarely intends for a format string to be externally-controlled at all. This weakness is frequently introduced in code that constructs log messages, where a constant format string is omitted.
Implementation	In cases such as localization and internationalization, the language-specific message repositories could be an avenue for exploitation, but the format string issue would be resultant, since attacker control of those repositories would also allow modification of message length, format, and content.

Applicable Platforms

Languages

C (Often Prevalent)

C++ (Often Prevalent)

Perl (Rarely Prevalent)

Common Consequences

Scope	Impact	Likelihood
Confidentiality	Technical Impact: Read Memory Format string problems allow for information disclosure which can severely simplify exploitation of the program.
Integrity Confidentiality Availability	Technical Impact: Modify Memory; Execute Unauthorized Code or Commands Format string problems can result in the execution of arbitrary code.

Likelihood Of Exploit

High

Demonstrative Examples

Example 1

The following program prints a string provided as an argument.

(bad code)

Example Language: C

#include <stdio.h>

void printWrapper(char *string) {

printf(string);

}

int main(int argc, char **argv) {

char buf[5012];
memcpy(buf, argv[1], 5012);
printWrapper(argv[1]);
return (0);

}

The example is exploitable, because of the call to printf() in the printWrapper() function. Note: The stack buffer was added to make exploitation more simple.

Example 2

The following code copies a command line argument into a buffer using snprintf().

(bad code)

Example Language: C

int main(int argc, char **argv){

char buf[128];
...
snprintf(buf,128,argv[1]);

}

This code allows an attacker to view the contents of the stack and write to the stack using a command line argument containing a sequence of formatting directives. The attacker can read from the stack by providing more formatting directives, such as %x, than the function takes as arguments to be formatted. (In this example, the function takes no arguments to be formatted.) By using the %n formatting directive, the attacker can write to the stack, causing snprintf() to write the number of bytes output thus far to the specified argument (rather than reading a value from the argument, which is the intended behavior). A sophisticated version of this attack will use four staggered writes to completely control the value of a pointer on the stack.

Example 3

Certain implementations make more advanced attacks even easier by providing format directives that control the location in memory to read from or write to. An example of these directives is shown in the following code, written for glibc:

(bad code)

Example Language: C

printf("%d %d %1$d %1$d\n", 5, 9);

This code produces the following output: 5 9 5 5 It is also possible to use half-writes (%hn) to accurately control arbitrary DWORDS in memory, which greatly reduces the complexity needed to execute an attack that would otherwise require four staggered writes, such as the one mentioned in the first example.

Observed Examples

Reference	Description
CVE-2002-1825	format string in Perl program
CVE-2001-0717	format string in bad call to syslog function
CVE-2002-0573	format string in bad call to syslog function
CVE-2002-1788	format strings in NNTP server responses
CVE-2006-2480	Format string vulnerability exploited by triggering errors or warnings, as demonstrated via format string specifiers in a .bmp filename.
CVE-2007-2027	Chain: untrusted search path enabling resultant format string by loading malicious internationalization messages

Potential Mitigations

Phase: Requirements

Choose a language that is not subject to this flaw.

Phase: Implementation

Ensure that all format string functions are passed a static string which cannot be controlled by the user, and that the proper number of arguments are always sent to that function as well. If at all possible, use functions that do not support the %n operator in format strings. [REF-116] [REF-117]

Phase: Build and Compilation

Run compilers and linkers with high warning levels, since they may detect incorrect usage.

Weakness Ordinalities

Ordinality	Description
Primary	(where the weakness exists independent of other weaknesses)

Detection Methods

Automated Static Analysis

This weakness can often be detected using automated static analysis tools. Many modern tools use data flow analysis or constraint-based techniques to minimize the number of false positives.

Black Box

Since format strings often occur in rarely-occurring erroneous conditions (e.g. for error message logging), they can be difficult to detect using black box methods. It is highly likely that many latent issues exist in executables that do not have associated source code (or equivalent source.

Effectiveness: Limited

Automated Static Analysis - Binary or Bytecode

According to SOAR, the following detection techniques may be useful:

Highly cost effective:

Bytecode Weakness Analysis - including disassembler + source code weakness analysis

Binary Weakness Analysis - including disassembler + source code weakness analysis

Cost effective for partial coverage:

Binary / Bytecode simple extractor - strings, ELF readers, etc.

Effectiveness: High

Manual Static Analysis - Binary or Bytecode

According to SOAR, the following detection techniques may be useful:

Cost effective for partial coverage:

Binary / Bytecode disassembler - then use manual analysis for vulnerabilities & anomalies

Effectiveness: SOAR Partial

Dynamic Analysis with Automated Results Interpretation

According to SOAR, the following detection techniques may be useful:

Cost effective for partial coverage:

Web Application Scanner

Web Services Scanner

Database Scanners

Effectiveness: SOAR Partial

Dynamic Analysis with Manual Results Interpretation

According to SOAR, the following detection techniques may be useful:

Cost effective for partial coverage:

Fuzz Tester

Framework-based Fuzzer

Effectiveness: SOAR Partial

Manual Static Analysis - Source Code

According to SOAR, the following detection techniques may be useful:

Highly cost effective:

Manual Source Code Review (not inspections)

Cost effective for partial coverage:

Focused Manual Spotcheck - Focused manual analysis of source

Effectiveness: High

Automated Static Analysis - Source Code

According to SOAR, the following detection techniques may be useful:

Highly cost effective:

Source code Weakness Analyzer

Context-configured Source Code Weakness Analyzer

Cost effective for partial coverage:

Warning Flags

Effectiveness: High

Architecture or Design Review

According to SOAR, the following detection techniques may be useful:

Highly cost effective:

Formal Methods / Correct-By-Construction

Cost effective for partial coverage:

Inspection (IEEE 1028 standard) (can apply to requirements, design, source code, etc.)

Effectiveness: High

Functional Areas

Logging
Error Handling
String Processing

Affected Resources

Memory

Memberships

Nature	Type	ID	Name
MemberOf	View - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries).	635	Weaknesses Originally Used by NVD from 2008 to 2016
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	726	OWASP Top Ten 2004 Category A5 - Buffer Overflows
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	743	CERT C Secure Coding Standard (2008) Chapter 10 - Input Output (FIO)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	808	2010 Top 25 - Weaknesses On the Cusp
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	845	The CERT Oracle Secure Coding Standard for Java (2011) Chapter 2 - Input Validation and Data Sanitization (IDS)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	865	2011 Top 25 - Risky Resource Management
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	877	CERT C++ Secure Coding Section 09 - Input Output (FIO)
MemberOf	View - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries).	884	CWE Cross-section
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	990	SFP Secondary Cluster: Tainted Input to Command
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1131	CISQ Quality Measures (2016) - Security
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1134	SEI CERT Oracle Secure Coding Standard for Java - Guidelines 00. Input Validation and Data Sanitization (IDS)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1163	SEI CERT C Coding Standard - Guidelines 09. Input Output (FIO)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1179	SEI CERT Perl Coding Standard - Guidelines 01. Input Validation and Data Sanitization (IDS)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1308	CISQ Quality Measures - Security
MemberOf	View - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries).	1340	CISQ Data Protection Measures
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1399	Comprehensive Categorization: Memory Safety

Vulnerability Mapping Notes

Usage: ALLOWED

(this CWE ID could be used to map to real-world vulnerabilities)

Reason: Acceptable-Use

Rationale:

This CWE entry is at the Base level of abstraction, which is a preferred level of abstraction for mapping to the root causes of vulnerabilities.

Comments:

Notes

Applicable Platform

This weakness is possible in any programming language that support format strings.

Research Gap

Format string issues are under-studied for languages other than C. Memory or disk consumption, control flow or variable alteration, and data corruption may result from format string exploitation in applications written in other languages such as Perl, PHP, Python, etc.

Other

While Format String vulnerabilities typically fall under the Buffer Overflow category, technically they are not overflowed buffers. The Format String vulnerability is fairly new (circa 1999) and stems from the fact that there is no realistic way for a function that takes a variable number of arguments to determine just how many arguments were passed in. The most common functions that take a variable number of arguments, including C-runtime functions, are the printf() family of calls. The Format String problem appears in a number of ways. A *printf() call without a format specifier is dangerous and can be exploited. For example, printf(input); is exploitable, while printf(y, input); is not exploitable in that context. The result of the first call, used incorrectly, allows for an attacker to be able to peek at stack memory since the input string will be used as the format specifier. The attacker can stuff the input string with format specifiers and begin reading stack values, since the remaining parameters will be pulled from the stack. Worst case, this improper use may give away enough control to allow an arbitrary value (or values in the case of an exploit program) to be written into the memory of the running program.

Frequently targeted entities are file names, process names, identifiers.

Format string problems are a classic C/C++ issue that are now rare due to the ease of discovery. One main reason format string vulnerabilities can be exploited is due to the %n operator. The %n operator will write the number of characters, which have been printed by the format string therefore far, to the memory pointed to by its argument. Through skilled creation of a format string, a malicious user may use values on the stack to create a write-what-where condition. Once this is achieved, they can execute arbitrary code. Other operators can be used as well; for example, a %9999s operator could also trigger a buffer overflow, or when used in file-formatting functions like fprintf, it can generate a much larger output than intended.

Taxonomy Mappings

Mapped Taxonomy Name	Node ID	Fit	Mapped Node Name
PLOVER			Format string vulnerability
7 Pernicious Kingdoms			Format String
CLASP			Format string problem
CERT C Secure Coding	FIO30-C	Exact	Exclude user input from format strings
CERT C Secure Coding	FIO47-C	CWE More Specific	Use valid format strings
OWASP Top Ten 2004	A1	CWE More Specific	Unvalidated Input
WASC	6		Format String
The CERT Oracle Secure Coding Standard for Java (2011)	IDS06-J		Exclude user input from format strings
SEI CERT Perl Coding Standard	IDS30-PL	Exact	Exclude user input from format strings
Software Fault Patterns	SFP24		Tainted input to command
OMG ASCSM	ASCSM-CWE-134

Related Attack Patterns

CAPEC-ID	Attack Pattern Name
CAPEC-135	Format String Injection
CAPEC-67	String Format Overflow in syslog()

References

[REF-116] Steve Christey. "Format String Vulnerabilities in Perl Programs". <https://seclists.org/fulldisclosure/2005/Dec/91>. URL validated: 2023-04-07.

[REF-117] Hal Burch and Robert C. Seacord. "Programming Language Format String Vulnerabilities". <https://drdobbs.com/security/programming-language-format-string-vulne/197002914>. URL validated: 2023-04-07.

[REF-118] Tim Newsham. "Format String Attacks". Guardent. 2000-09-09. <http://www.thenewsh.com/~newsham/format-string-attacks.pdf>.

[REF-7] Michael Howard and David LeBlanc. "Writing Secure Code". Chapter 5, "Format String Bugs" Page 147. 2nd Edition. Microsoft Press. 2002-12-04. <https://www.microsoftpressstore.com/store/writing-secure-code-9780735617223>.

[REF-44] Michael Howard, David LeBlanc and John Viega. "24 Deadly Sins of Software Security". "Sin 6: Format String Problems." Page 109. McGraw-Hill. 2010.

[REF-62] Mark Dowd, John McDonald and Justin Schuh. "The Art of Software Security Assessment". Chapter 8, "C Format Strings", Page 422. 1st Edition. Addison Wesley. 2006.

[REF-962] Object Management Group (OMG). "Automated Source Code Security Measure (ASCSM)". ASCSM-CWE-134. 2016-01. <http://www.omg.org/spec/ASCSM/1.0/>.

Content History

Submissions
Submission Date	Submitter	Organization
2006-07-19 (CWE Draft 3, 2006-07-19)	PLOVER
2006-07-19 (CWE Draft 3, 2006-07-19)
Modifications
Modification Date	Modifier	Organization
2008-08-01		KDM Analytics
2008-08-01	added/updated white box definitions
2008-09-08	CWE Content Team	MITRE
2008-09-08	updated Applicable_Platforms, Common_Consequences, Detection_Factors, Modes_of_Introduction, Relationships, Other_Notes, Research_Gaps, Taxonomy_Mappings, Weakness_Ordinalities
2008-11-24	CWE Content Team	MITRE
2008-11-24	updated Relationships, Taxonomy_Mappings
2009-03-10	CWE Content Team	MITRE
2009-03-10	updated Relationships
2009-05-27	CWE Content Team	MITRE
2009-05-27	updated Demonstrative_Examples
2009-07-17	KDM Analytics
2009-07-17	Improved the White_Box_Definition
2009-07-27	CWE Content Team	MITRE
2009-07-27	updated White_Box_Definitions
2010-02-16	CWE Content Team	MITRE
2010-02-16	updated Detection_Factors, References, Relationships, Taxonomy_Mappings
2011-06-01	CWE Content Team	MITRE
2011-06-01	updated Common_Consequences, Relationships, Taxonomy_Mappings
2011-06-27	CWE Content Team	MITRE
2011-06-27	updated Modes_of_Introduction, Relationships
2011-09-13	CWE Content Team	MITRE
2011-09-13	updated Potential_Mitigations, References, Relationships, Taxonomy_Mappings
2012-05-11	CWE Content Team	MITRE
2012-05-11	updated Observed_Examples, References, Related_Attack_Patterns, Relationships, Taxonomy_Mappings
2014-07-30	CWE Content Team	MITRE
2014-07-30	updated Demonstrative_Examples, Detection_Factors, Relationships, Taxonomy_Mappings
2015-12-07	CWE Content Team	MITRE
2015-12-07	updated Description, Modes_of_Introduction, Name, Relationships
2017-11-08	CWE Content Team	MITRE
2017-11-08	updated Applicable_Platforms, Causal_Nature, Functional_Areas, Likelihood_of_Exploit, Other_Notes, References, Relationships, Taxonomy_Mappings, White_Box_Definitions
2018-03-27	CWE Content Team	MITRE
2018-03-27	updated References
2019-01-03	CWE Content Team	MITRE
2019-01-03	updated References, Relationships, Taxonomy_Mappings
2019-06-20	CWE Content Team	MITRE
2019-06-20	updated Relationships
2019-09-19	CWE Content Team	MITRE
2019-09-19	updated Relationships
2020-02-24	CWE Content Team	MITRE
2020-02-24	updated Detection_Factors, Relationships
2020-08-20	CWE Content Team	MITRE
2020-08-20	updated Relationships
2020-12-10	CWE Content Team	MITRE
2020-12-10	updated Common_Consequences, Relationships
2021-03-15	CWE Content Team	MITRE
2021-03-15	updated Potential_Mitigations, Relationships
2023-01-31	CWE Content Team	MITRE
2023-01-31	updated Description
2023-04-27	CWE Content Team	MITRE
2023-04-27	updated References, Relationships
2023-06-29	CWE Content Team	MITRE
2023-06-29	updated Mapping_Notes
Previous Entry Names
Change Date	Previous Entry Name
2015-12-07	Uncontrolled Format String

Weakness ID: 477

View customized information:

Description

The code uses deprecated or obsolete functions, which suggests that the code has not been actively reviewed or maintained.

Extended Description

As programming languages evolve, functions occasionally become obsolete due to:

Advances in the language
Improved understanding of how operations should be performed effectively and securely
Changes in the conventions that govern certain operations

Functions that are removed are usually replaced by newer counterparts that perform the same task in some different and hopefully improved way.

Relationships

Relevant to the view "Research Concepts" (CWE-1000)

Nature	Type	ID	Name
ChildOf	Pillar - a weakness that is the most abstract type of weakness and represents a theme for all class/base/variant weaknesses related to it. A Pillar is different from a Category as a Pillar is still technically a type of weakness that describes a mistake, while a Category represents a common characteristic used to group related things.	710	Improper Adherence to Coding Standards

Relevant to the view "Software Development" (CWE-699)

Nature	Type	ID	Name
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1228	API / Function Errors

Modes Of Introduction

Phase	Note
Implementation

Applicable Platforms

Languages

Class: Not Language-Specific (Undetermined Prevalence)

Common Consequences

Scope	Impact	Likelihood
Other	Technical Impact: Quality Degradation

Demonstrative Examples

Example 1

The following code uses the deprecated function getpw() to verify that a plaintext password matches a user's encrypted password. If the password is valid, the function sets result to 1; otherwise it is set to 0.

(bad code)

Example Language: C

...
getpw(uid, pwdline);
for (i=0; i<3; i++){

cryptpw=strtok(pwdline, ":");
pwdline=0;

}
result = strcmp(crypt(plainpw,cryptpw), cryptpw) == 0;
...

Although the code often behaves correctly, using the getpw() function can be problematic from a security standpoint, because it can overflow the buffer passed to its second parameter. Because of this vulnerability, getpw() has been supplanted by getpwuid(), which performs the same lookup as getpw() but returns a pointer to a statically-allocated structure to mitigate the risk. Not all functions are deprecated or replaced because they pose a security risk. However, the presence of an obsolete function often indicates that the surrounding code has been neglected and may be in a state of disrepair. Software security has not been a priority, or even a consideration, for very long. If the program uses deprecated or obsolete functions, it raises the probability that there are security problems lurking nearby.

Example 2

In the following code, the programmer assumes that the system always has a property named "cmd" defined. If an attacker can control the program's environment so that "cmd" is not defined, the program throws a null pointer exception when it attempts to call the "Trim()" method.

(bad code)

Example Language: Java

String cmd = null;
...
cmd = Environment.GetEnvironmentVariable("cmd");
cmd = cmd.Trim();

Example 3

The following code constructs a string object from an array of bytes and a value that specifies the top 8 bits of each 16-bit Unicode character.

(bad code)

Example Language: Java

...
String name = new String(nameBytes, highByte);
...

In this example, the constructor may not correctly convert bytes to characters depending upon which charset is used to encode the string represented by nameBytes. Due to the evolution of the charsets used to encode strings, this constructor was deprecated and replaced by a constructor that accepts as one of its parameters the name of the charset used to encode the bytes for conversion.

Potential Mitigations

Phase: Implementation

Refer to the documentation for the obsolete function in order to determine why it is deprecated or obsolete and to learn about alternative ways to achieve the same functionality.

Phase: Requirements

Consider seriously the security implications of using an obsolete function. Consider using alternate functions.

Weakness Ordinalities

Ordinality	Description
Indirect	(where the weakness is a quality issue that might indirectly make it easier to introduce security-relevant weaknesses or make them more difficult to detect)

Detection Methods

Automated Static Analysis - Binary or Bytecode

According to SOAR, the following detection techniques may be useful:

Highly cost effective:

Binary / Bytecode Quality Analysis

Cost effective for partial coverage:

Bytecode Weakness Analysis - including disassembler + source code weakness analysis

Effectiveness: High

Manual Static Analysis - Binary or Bytecode

According to SOAR, the following detection techniques may be useful:

Cost effective for partial coverage:

Binary / Bytecode disassembler - then use manual analysis for vulnerabilities & anomalies

Effectiveness: SOAR Partial

Dynamic Analysis with Manual Results Interpretation

According to SOAR, the following detection techniques may be useful:

Highly cost effective:

Debugger

Effectiveness: High

Manual Static Analysis - Source Code

According to SOAR, the following detection techniques may be useful:

Highly cost effective:

Manual Source Code Review (not inspections)

Cost effective for partial coverage:

Focused Manual Spotcheck - Focused manual analysis of source

Effectiveness: High

Automated Static Analysis - Source Code

According to SOAR, the following detection techniques may be useful:

Highly cost effective:

Source Code Quality Analyzer

Source code Weakness Analyzer

Context-configured Source Code Weakness Analyzer

Effectiveness: High

Automated Static Analysis

According to SOAR, the following detection techniques may be useful:

Highly cost effective:

Origin Analysis

Effectiveness: High

Architecture or Design Review

According to SOAR, the following detection techniques may be useful:

Highly cost effective:

Formal Methods / Correct-By-Construction

Inspection (IEEE 1028 standard) (can apply to requirements, design, source code, etc.)

Effectiveness: High

Memberships

Nature	Type	ID	Name
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	398	7PK - Code Quality
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1001	SFP Secondary Cluster: Use of an Improper API
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1180	SEI CERT Perl Coding Standard - Guidelines 02. Declarations and Initialization (DCL)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1181	SEI CERT Perl Coding Standard - Guidelines 03. Expressions (EXP)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1308	CISQ Quality Measures - Security
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1412	Comprehensive Categorization: Poor Coding Practices

Vulnerability Mapping Notes

Usage: ALLOWED

(this CWE ID could be used to map to real-world vulnerabilities)

Reason: Acceptable-Use

Rationale:

This CWE entry is at the Base level of abstraction, which is a preferred level of abstraction for mapping to the root causes of vulnerabilities.

Comments:

Taxonomy Mappings

Mapped Taxonomy Name	Node ID	Fit	Mapped Node Name
7 Pernicious Kingdoms			Obsolete
Software Fault Patterns	SFP3		Use of an improper API
SEI CERT Perl Coding Standard	DCL30-PL	CWE More Specific	Do not import deprecated modules
SEI CERT Perl Coding Standard	EXP30-PL	CWE More Specific	Do not use deprecated or obsolete functions or modules

References

Content History

Submissions
Submission Date	Submitter	Organization
2006-07-19 (CWE Draft 3, 2006-07-19)	7 Pernicious Kingdoms
2006-07-19 (CWE Draft 3, 2006-07-19)
Modifications
Modification Date	Modifier	Organization
2008-07-01	Eric Dalci	Cigital
2008-07-01	updated Potential_Mitigations, Time_of_Introduction
2008-09-08	CWE Content Team	MITRE
2008-09-08	updated Relationships, Other_Notes, Taxonomy_Mappings
2009-03-10	CWE Content Team	MITRE
2009-03-10	updated Other_Notes
2009-05-27	CWE Content Team	MITRE
2009-05-27	updated Demonstrative_Examples
2009-07-27	CWE Content Team	MITRE
2009-07-27	updated Demonstrative_Examples
2011-03-29	CWE Content Team	MITRE
2011-03-29	updated Demonstrative_Examples
2011-06-01	CWE Content Team	MITRE
2011-06-01	updated Common_Consequences
2011-06-27	CWE Content Team	MITRE
2011-06-27	updated Common_Consequences
2012-05-11	CWE Content Team	MITRE
2012-05-11	updated Relationships
2012-10-30	CWE Content Team	MITRE
2012-10-30	updated Potential_Mitigations
2014-06-23	CWE Content Team	MITRE
2014-06-23	updated Description, Other_Notes, Potential_Mitigations
2014-07-30	CWE Content Team	MITRE
2014-07-30	updated Detection_Factors, Relationships, Taxonomy_Mappings
2017-11-08	CWE Content Team	MITRE
2017-11-08	updated Applicable_Platforms, Name, Relationships, Taxonomy_Mappings
2019-01-03	CWE Content Team	MITRE
2019-01-03	updated Taxonomy_Mappings, Weakness_Ordinalities
2020-02-24	CWE Content Team	MITRE
2020-02-24	updated References, Relationships
2020-08-20	CWE Content Team	MITRE
2020-08-20	updated Relationships
2021-03-15	CWE Content Team	MITRE
2021-03-15	updated Relationships
2023-04-27	CWE Content Team	MITRE
2023-04-27	updated Relationships
2023-06-29	CWE Content Team	MITRE
2023-06-29	updated Mapping_Notes
Previous Entry Names
Change Date	Previous Entry Name
2008-01-30	Obsolete

2017-11-08	Use of Obsolete Functions

Weakness ID: 457

View customized information:

Description

The code uses a variable that has not been initialized, leading to unpredictable or unintended results.

Extended Description

In some languages such as C and C++, stack variables are not initialized by default. They generally contain junk data with the contents of stack memory before the function was invoked. An attacker can sometimes control or read these contents. In other languages or conditions, a variable that is not explicitly initialized can be given a default value that has security implications, depending on the logic of the program. The presence of an uninitialized variable can sometimes indicate a typographic error in the code.

Relationships

Relevant to the view "Research Concepts" (CWE-1000)

Nature	Type	ID	Name
ChildOf	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	908	Use of Uninitialized Resource
CanFollow	Variant - a weakness that is linked to a certain type of product, typically involving a specific language or technology. More specific than a Base weakness. Variant level weaknesses typically describe issues in terms of 3 to 5 of the following dimensions: behavior, property, technology, language, and resource.	456	Missing Initialization of a Variable

Relevant to the view "CISQ Quality Measures (2020)" (CWE-1305)

Nature	Type	ID	Name
ChildOf	Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource.	665	Improper Initialization

Relevant to the view "CISQ Data Protection Measures" (CWE-1340)

Nature	Type	ID	Name
ChildOf	Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource.	665	Improper Initialization

Modes Of Introduction

Phase	Note
Implementation	In C, using an uninitialized char * in some string libraries will return incorrect results, as the libraries expect the null terminator to always be at the end of a string, even if the string is empty.

Applicable Platforms

Languages

C (Sometimes Prevalent)

C++ (Sometimes Prevalent)

Perl (Often Prevalent)

PHP (Often Prevalent)

Class: Not Language-Specific (Undetermined Prevalence)

Common Consequences

Scope	Impact	Likelihood
Availability Integrity Other	Technical Impact: Other Initial variables usually contain junk, which can not be trusted for consistency. This can lead to denial of service conditions, or modify control flow in unexpected ways. In some cases, an attacker can "pre-initialize" the variable using previous actions, which might enable code execution. This can cause a race condition if a lock variable check passes when it should not.
Authorization Other	Technical Impact: Other Strings that are not initialized are especially dangerous, since many functions expect a null at the end -- and only at the end -- of a string.

Likelihood Of Exploit

High

Demonstrative Examples

Example 1

This code prints a greeting using information stored in a POST request:

(bad code)

Example Language: PHP

if (isset($_POST['names'])) {

$nameArray = $_POST['names'];

}
echo "Hello " . $nameArray['first'];

This code checks if the POST array 'names' is set before assigning it to the $nameArray variable. However, if the array is not in the POST request, $nameArray will remain uninitialized. This will cause an error when the array is accessed to print the greeting message, which could lead to further exploit.

Example 2

The following switch statement is intended to set the values of the variables aN and bN before they are used:

(bad code)

Example Language: C

int aN, Bn;
switch (ctl) {

case -1:

aN = 0;
bN = 0;
break;

case 0:

aN = i;
bN = -i;
break;

case 1:

aN = i + NEXT_SZ;
bN = i - NEXT_SZ;
break;

default:

aN = -1;
aN = -1;
break;

}
repaint(aN, bN);

In the default case of the switch statement, the programmer has accidentally set the value of aN twice. As a result, bN will have an undefined value. Most uninitialized variable issues result in general software reliability problems, but if attackers can intentionally trigger the use of an uninitialized variable, they might be able to launch a denial of service attack by crashing the program. Under the right circumstances, an attacker may be able to control the value of an uninitialized variable by affecting the values on the stack prior to the invocation of the function.

Example 3

(bad code)

Example Language: C

char *test_string;
if (i != err_val)
{

test_string = "Hello World!";

}
printf("%s", test_string);

When the printf() is reached, test_string might be an unexpected address, so the printf might print junk strings (CWE-457).

To fix this code, there are a couple approaches to making sure that test_string has been properly set once it reaches the printf().

One solution would be to set test_string to an acceptable default before the conditional:

(good code)

Example Language: C

char *test_string = "Done at the beginning";
if (i != err_val)
{

test_string = "Hello World!";

}
printf("%s", test_string);

Another solution is to ensure that each branch of the conditional - including the default/else branch - could ensure that test_string is set:

(good code)

Example Language: C

char *test_string;
if (i != err_val)
{

test_string = "Hello World!";

}
else {

test_string = "Done on the other side!";

}
printf("%s", test_string);

Observed Examples

Reference	Description
CVE-2019-15900	Chain: sscanf() call is used to check if a username and group exists, but the return value of sscanf() call is not checked (CWE-252), causing an uninitialized variable to be checked (CWE-457), returning success to allow authorization bypass for executing a privileged (CWE-863).
CVE-2008-3688	Chain: A denial of service may be caused by an uninitialized variable (CWE-457) allowing an infinite loop (CWE-835) resulting from a connection to an unresponsive server.
CVE-2008-0081	Uninitialized variable leads to code execution in popular desktop application.
CVE-2007-4682	Crafted input triggers dereference of an uninitialized object pointer.
CVE-2007-3468	Crafted audio file triggers crash when an uninitialized variable is used.
CVE-2007-2728	Uninitialized random seed variable used.

Potential Mitigations

Phase: Implementation

Strategy: Attack Surface Reduction

Assign all variables to an initial value.

Phase: Build and Compilation

Strategy: Compilation or Build Hardening

Most compilers will complain about the use of uninitialized variables if warnings are turned on.

Phases: Implementation; Operation

When using a language that does not require explicit declaration of variables, run or compile the software in a mode that reports undeclared or unknown variables. This may indicate the presence of a typographic error in the variable's name.

Phase: Requirements

The choice could be made to use a language that is not susceptible to these issues.

Phase: Architecture and Design

Mitigating technologies such as safe string libraries and container abstractions could be introduced.

Detection Methods

Fuzzing

Effectiveness: High

Automated Static Analysis

Effectiveness: High

Memberships

Nature	Type	ID	Name
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	398	7PK - Code Quality
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	998	SFP Secondary Cluster: Glitch in Computation
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1180	SEI CERT Perl Coding Standard - Guidelines 02. Declarations and Initialization (DCL)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1416	Comprehensive Categorization: Resource Lifecycle Management

Vulnerability Mapping Notes

Usage: ALLOWED

(this CWE ID could be used to map to real-world vulnerabilities)

Reason: Acceptable-Use

Rationale:

This CWE entry is at the Variant level of abstraction, which is a preferred level of abstraction for mapping to the root causes of vulnerabilities.

Comments:

Taxonomy Mappings

Mapped Taxonomy Name	Node ID	Fit	Mapped Node Name
CLASP			Uninitialized variable
7 Pernicious Kingdoms			Uninitialized Variable
Software Fault Patterns	SFP1		Glitch in computation
SEI CERT Perl Coding Standard	DCL33-PL	Imprecise	Declare identifiers before using them

References

[REF-18] Secure Software, Inc.. "The CLASP Application Security Process". 2005. <https://cwe.mitre.org/documents/sources/TheCLASPApplicationSecurityProcess.pdf>.

[REF-436] mercy. "Exploiting Uninitialized Data". 2006-01. <http://www.felinemenace.org/~mercy/papers/UBehavior/UBehavior.zip>.

[REF-437] Microsoft Security Vulnerability Research & Defense. "MS08-014 : The Case of the Uninitialized Stack Variable Vulnerability". 2008-03-11. <https://msrc.microsoft.com/blog/2008/03/ms08-014-the-case-of-the-uninitialized-stack-variable-vulnerability/>. URL validated: 2023-04-07.

[REF-44] Michael Howard, David LeBlanc and John Viega. "24 Deadly Sins of Software Security". "Sin 8: C++ Catastrophes." Page 143. McGraw-Hill. 2010.

[REF-62] Mark Dowd, John McDonald and Justin Schuh. "The Art of Software Security Assessment". Chapter 7, "Variable Initialization", Page 312. 1st Edition. Addison Wesley. 2006.

Content History

Submissions
Submission Date	Submitter	Organization
2006-07-19 (CWE Draft 3, 2006-07-19)	CLASP
2006-07-19 (CWE Draft 3, 2006-07-19)
Modifications
Modification Date	Modifier	Organization
2008-07-01	Eric Dalci	Cigital
2008-07-01	updated Time_of_Introduction
2008-08-01		KDM Analytics
2008-08-01	added/updated white box definitions
2008-09-08	CWE Content Team	MITRE
2008-09-08	updated Applicable_Platforms, Common_Consequences, Description, Relationships, Observed_Example, Other_Notes, References, Taxonomy_Mappings
2009-01-12	CWE Content Team	MITRE
2009-01-12	updated Common_Consequences, Demonstrative_Examples, Potential_Mitigations
2009-03-10	CWE Content Team	MITRE
2009-03-10	updated Demonstrative_Examples
2009-05-27	CWE Content Team	MITRE
2009-05-27	updated Demonstrative_Examples
2011-06-01	CWE Content Team	MITRE
2011-06-01	updated Common_Consequences
2012-05-11	CWE Content Team	MITRE
2012-05-11	updated References, Relationships
2012-10-30	CWE Content Team	MITRE
2012-10-30	updated Demonstrative_Examples
2013-02-21	CWE Content Team	MITRE
2013-02-21	updated Applicable_Platforms, Description, Other_Notes, Potential_Mitigations, Relationships
2014-06-23	CWE Content Team	MITRE
2014-06-23	updated Modes_of_Introduction, Other_Notes
2014-07-30	CWE Content Team	MITRE
2014-07-30	updated Relationships, Taxonomy_Mappings
2017-11-08	CWE Content Team	MITRE
2017-11-08	updated References, Relationships, Taxonomy_Mappings, White_Box_Definitions
2019-01-03	CWE Content Team	MITRE
2019-01-03	updated Taxonomy_Mappings
2019-06-20	CWE Content Team	MITRE
2019-06-20	updated Relationships, Type
2020-02-24	CWE Content Team	MITRE
2020-02-24	updated References, Relationships, Type
2020-08-20	CWE Content Team	MITRE
2020-08-20	updated Relationships
2020-12-10	CWE Content Team	MITRE
2020-12-10	updated Relationships
2021-03-15	CWE Content Team	MITRE
2021-03-15	updated Demonstrative_Examples, Observed_Examples, Relationships
2021-07-20	CWE Content Team	MITRE
2021-07-20	updated Observed_Examples
2023-04-27	CWE Content Team	MITRE
2023-04-27	updated Detection_Factors, References, Relationships
2023-06-29	CWE Content Team	MITRE
2023-06-29	updated Mapping_Notes
Previous Entry Names
Change Date	Previous Entry Name
2008-04-11	Uninitialized Variable

Weakness ID: 597

View customized information:

Description

The product uses the wrong operator when comparing a string, such as using "==" when the .equals() method should be used instead.

Extended Description

In Java, using == or != to compare two strings for equality actually compares two objects for equality rather than their string values for equality. Chances are good that the two references will never be equal. While this weakness often only affects program correctness, if the equality is used for a security decision, the unintended comparison result could be leveraged to affect program security.

Relationships

Relevant to the view "Research Concepts" (CWE-1000)

Nature	Type	ID	Name
ChildOf	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	480	Use of Incorrect Operator
ChildOf	Variant - a weakness that is linked to a certain type of product, typically involving a specific language or technology. More specific than a Base weakness. Variant level weaknesses typically describe issues in terms of 3 to 5 of the following dimensions: behavior, property, technology, language, and resource.	595	Comparison of Object References Instead of Object Contents

Relevant to the view "CISQ Quality Measures (2020)" (CWE-1305)

Nature	Type	ID	Name
ChildOf	Variant - a weakness that is linked to a certain type of product, typically involving a specific language or technology. More specific than a Base weakness. Variant level weaknesses typically describe issues in terms of 3 to 5 of the following dimensions: behavior, property, technology, language, and resource.	595	Comparison of Object References Instead of Object Contents

Modes Of Introduction

Phase	Note
Implementation

Common Consequences

Scope	Impact	Likelihood
Other	Technical Impact: Other

Demonstrative Examples

Example 1

In the example below, two Java String objects are declared and initialized with the same string values. An if statement is used to determine if the strings are equivalent.

(bad code)

Example Language: Java

String str1 = new String("Hello");
String str2 = new String("Hello");
if (str1 == str2) {

System.out.println("str1 == str2");

}

However, the if statement will not be executed as the strings are compared using the "==" operator. For Java objects, such as String objects, the "==" operator compares object references, not object values. While the two String objects above contain the same string values, they refer to different object references, so the System.out.println statement will not be executed. To compare object values, the previous code could be modified to use the equals method:

(good code)

if (str1.equals(str2)) {

System.out.println("str1 equals str2");

}

Example 2

In the example below, three JavaScript variables are declared and initialized with the same values. Note that JavaScript will change a value between numeric and string as needed, which is the reason an integer is included with the strings. An if statement is used to determine whether the values are the same.

(bad code)

Example Language: JavaScript

<p id="ieq3s1" type="text">(i === s1) is FALSE</p>
<p id="s4eq3i" type="text">(s4 === i) is FALSE</p>
<p id="s4eq3s1" type="text">(s4 === s1) is FALSE</p>

var i = 65;
var s1 = '65';
var s4 = new String('65');

if (i === s1)
{

document.getElementById("ieq3s1").innerHTML = "(i === s1) is TRUE";

}

if (s4 === i)
{

document.getElementById("s4eq3i").innerHTML = "(s4 === i) is TRUE";

}

if (s4 === s1)
{

document.getElementById("s4eq3s1").innerHTML = "(s4 === s1) is TRUE";

}

However, the body of the if statement will not be executed, as the "===" compares both the type of the variable AND the value. As the types of the first comparison are number and string, it fails. The types in the second are int and reference, so this one fails as well. The types in the third are reference and string, so it also fails.

While the variables above contain the same values, they are contained in different types, so the document.getElementById... statement will not be executed in any of the cases.

To compare object values, the previous code is modified and shown below to use the "==" for value comparison so the comparison in this example executes the HTML statement:

(good code)

Example Language: JavaScript

<p id="ieq2s1" type="text">(i == s1) is FALSE</p>
<p id="s4eq2i" type="text">(s4 == i) is FALSE</p>
<p id="s4eq2s1" type="text">(s4 == s1) is FALSE</p>

var i = 65;
var s1 = '65';
var s4 = new String('65');

if (i == s1)
{

document.getElementById("ieq2s1").innerHTML = "(i == s1) is TRUE";

}

if (s4 == i)
{

document.getElementById("s4eq2i").innerHTML = "(s4 == i) is TRUE";

}

if (s4 == s1)
{

document.getElementById("s4eq2s1").innerHTML = "(s4 == s1) is TRUE";

}

Example 3

In the example below, two PHP variables are declared and initialized with the same numbers - one as a string, the other as an integer. Note that PHP will change the string value to a number for a comparison. An if statement is used to determine whether the values are the same.

(bad code)

Example Language: PHP

var $i = 65;
var $s1 = "65";

if ($i === $s1)
{

echo '($i === $s1) is TRUE'. "\n";

}
else
{

echo '($i === $s1) is FALSE'. "\n";

}

However, the body of the if statement will not be executed, as the "===" compares both the type of the variable AND the value. As the types of the first comparison are number and string, it fails.

While the variables above contain the same values, they are contained in different types, so the TRUE portion of the if statement will not be executed.

To compare object values, the previous code is modified and shown below to use the "==" for value comparison (string converted to number) so the comparison in this example executes the TRUE statement:

(good code)

Example Language: PHP

var $i = 65;
var $s1 = "65";

if ($i == $s1)
{

echo '($i == $s1) is TRUE'. "\n";

}
else
{

echo '($i == $s1) is FALSE'. "\n";

}

Potential Mitigations

Phase: Implementation

Within Java, use .equals() to compare string values.

Within JavaScript, use == to compare string values.

Within PHP, use == to compare a numeric value to a string value. (PHP converts the string to a number.)

Effectiveness: High

Detection Methods

Automated Static Analysis

Effectiveness: High

Memberships

Nature	Type	ID	Name
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	847	The CERT Oracle Secure Coding Standard for Java (2011) Chapter 4 - Expressions (EXP)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	998	SFP Secondary Cluster: Glitch in Computation
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1136	SEI CERT Oracle Secure Coding Standard for Java - Guidelines 02. Expressions (EXP)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1181	SEI CERT Perl Coding Standard - Guidelines 03. Expressions (EXP)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1397	Comprehensive Categorization: Comparison

Vulnerability Mapping Notes

Usage: ALLOWED

(this CWE ID could be used to map to real-world vulnerabilities)

Reason: Acceptable-Use

Rationale:

This CWE entry is at the Variant level of abstraction, which is a preferred level of abstraction for mapping to the root causes of vulnerabilities.

Comments:

Taxonomy Mappings

Mapped Taxonomy Name	Node ID	Fit	Mapped Node Name
The CERT Oracle Secure Coding Standard for Java (2011)	EXP03-J		Do not use the equality operators when comparing values of boxed primitives
The CERT Oracle Secure Coding Standard for Java (2011)	EXP03-J		Do not use the equality operators when comparing values of boxed primitives
SEI CERT Perl Coding Standard	EXP35-PL	CWE More Specific	Use the correct operator type for comparing values
Software Fault Patterns	SFP1		Glitch in computation

References

[REF-62] Mark Dowd, John McDonald and Justin Schuh. "The Art of Software Security Assessment". Chapter 6, "Typos", Page 289. 1st Edition. Addison Wesley. 2006.

Content History

Submissions
Submission Date	Submitter	Organization
2006-12-15 (CWE Draft 5, 2006-12-15)	CWE Content Team	MITRE
2006-12-15 (CWE Draft 5, 2006-12-15)
Modifications
Modification Date	Modifier	Organization
2008-07-01	Eric Dalci	Cigital
2008-07-01	updated Potential_Mitigations, Time_of_Introduction
2008-09-08	CWE Content Team	MITRE
2008-09-08	updated Description, Relationships
2008-10-14	CWE Content Team	MITRE
2008-10-14	updated Relationships
2009-05-27	CWE Content Team	MITRE
2009-05-27	updated Demonstrative_Examples
2011-03-29	CWE Content Team	MITRE
2011-03-29	updated Demonstrative_Examples, Description, Potential_Mitigations
2011-06-01	CWE Content Team	MITRE
2011-06-01	updated Common_Consequences, Relationships, Taxonomy_Mappings
2012-05-11	CWE Content Team	MITRE
2012-05-11	updated Demonstrative_Examples, References, Relationships, Taxonomy_Mappings
2014-07-30	CWE Content Team	MITRE
2014-07-30	updated Relationships, Taxonomy_Mappings
2017-11-08	CWE Content Team	MITRE
2017-11-08	updated Taxonomy_Mappings
2019-01-03	CWE Content Team	MITRE
2019-01-03	updated Relationships, Taxonomy_Mappings
2020-02-24	CWE Content Team	MITRE
2020-02-24	updated Relationships
2020-08-20	CWE Content Team	MITRE
2020-08-20	updated Relationships
2021-03-15	CWE Content Team	MITRE
2021-03-15	updated Demonstrative_Examples, Description, Potential_Mitigations, Relationships
2023-04-27	CWE Content Team	MITRE
2023-04-27	updated Detection_Factors, Relationships
2023-06-29	CWE Content Team	MITRE
2023-06-29	updated Mapping_Notes
Previous Entry Names
Change Date	Previous Entry Name
2008-04-11	Erroneous String Compare

Common Weakness Enumeration

CWE VIEW: Weaknesses Addressed by the SEI CERT Perl Coding Standard

View Components

CWE-767: Access to Critical Private Variable via Public Method

CWE-563: Assignment to Variable without Use

CWE-561: Dead Code

CWE-628: Function Call with Incorrectly Specified Arguments

CWE-754: Improper Check for Unusual or Exceptional Conditions

CWE-460: Improper Cleanup on Thrown Exception

CWE-116: Improper Encoding or Escaping of Output

CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')

CWE-59: Improper Link Resolution Before File Access ('Link Following')

CWE-95: Improper Neutralization of Directives in Dynamically Evaluated Code ('Eval Injection')

CWE-77: Improper Neutralization of Special Elements used in a Command ('Command Injection')

CWE-129: Improper Validation of Array Index

CWE-705: Incorrect Control Flow Scoping

CWE-789: Memory Allocation with Excessive Size Value

CWE-456: Missing Initialization of a Variable

CWE CATEGORY: Numeric Errors

CWE-783: Operator Precedence Logic Error

CWE-375: Returning a Mutable Object to an Untrusted Caller

CWE CATEGORY: SEI CERT Perl Coding Standard - Guidelines 01. Input Validation and Data Sanitization (IDS)

CWE CATEGORY: SEI CERT Perl Coding Standard - Guidelines 02. Declarations and Initialization (DCL)

CWE CATEGORY: SEI CERT Perl Coding Standard - Guidelines 03. Expressions (EXP)

CWE CATEGORY: SEI CERT Perl Coding Standard - Guidelines 04. Integers (INT)

CWE CATEGORY: SEI CERT Perl Coding Standard - Guidelines 05. Strings (STR)

CWE CATEGORY: SEI CERT Perl Coding Standard - Guidelines 06. Object-Oriented Programming (OOP)

CWE CATEGORY: SEI CERT Perl Coding Standard - Guidelines 07. File Input and Output (FIO)

CWE CATEGORY: SEI CERT Perl Coding Standard - Guidelines 50. Miscellaneous (MSC)

CWE-248: Uncaught Exception

CWE-391: Unchecked Error Condition

CWE-252: Unchecked Return Value

CWE-690: Unchecked Return Value to NULL Pointer Dereference

CWE-394: Unexpected Status Code or Return Value

CWE-134: Use of Externally-Controlled Format String

CWE-477: Use of Obsolete Function

CWE-457: Use of Uninitialized Variable

CWE-597: Use of Wrong Operator in String Comparison

Common Weakness Enumeration

CWE VIEW: Weaknesses Addressed by the SEI CERT Perl Coding Standard

View Components

CWE-767: Access to Critical Private Variable via Public Method

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CWE-563: Assignment to Variable without Use

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CWE-561: Dead Code

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CWE-628: Function Call with Incorrectly Specified Arguments

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CWE-754: Improper Check for Unusual or Exceptional Conditions

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CWE-460: Improper Cleanup on Thrown Exception

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CWE-116: Improper Encoding or Escaping of Output

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CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')

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CWE-59: Improper Link Resolution Before File Access ('Link Following')

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CWE-95: Improper Neutralization of Directives in Dynamically Evaluated Code ('Eval Injection')

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CWE-77: Improper Neutralization of Special Elements used in a Command ('Command Injection')

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CWE-129: Improper Validation of Array Index

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CWE-705: Incorrect Control Flow Scoping

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CWE-789: Memory Allocation with Excessive Size Value

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CWE-456: Missing Initialization of a Variable

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CWE CATEGORY: Numeric Errors

CWE-783: Operator Precedence Logic Error

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CWE-375: Returning a Mutable Object to an Untrusted Caller

Edit Custom Filter

CWE CATEGORY: SEI CERT Perl Coding Standard - Guidelines 01. Input Validation and Data Sanitization (IDS)

CWE CATEGORY: SEI CERT Perl Coding Standard - Guidelines 02. Declarations and Initialization (DCL)

CWE CATEGORY: SEI CERT Perl Coding Standard - Guidelines 03. Expressions (EXP)

CWE CATEGORY: SEI CERT Perl Coding Standard - Guidelines 04. Integers (INT)

CWE CATEGORY: SEI CERT Perl Coding Standard - Guidelines 05. Strings (STR)

CWE CATEGORY: SEI CERT Perl Coding Standard - Guidelines 06. Object-Oriented Programming (OOP)

CWE CATEGORY: SEI CERT Perl Coding Standard - Guidelines 07. File Input and Output (FIO)

CWE CATEGORY: SEI CERT Perl Coding Standard - Guidelines 50. Miscellaneous (MSC)

CWE-248: Uncaught Exception

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CWE-391: Unchecked Error Condition

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CWE-252: Unchecked Return Value

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CWE-690: Unchecked Return Value to NULL Pointer Dereference

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CWE-394: Unexpected Status Code or Return Value

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CWE-134: Use of Externally-Controlled Format String

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CWE-477: Use of Obsolete Function

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CWE-457: Use of Uninitialized Variable

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CWE-597: Use of Wrong Operator in String Comparison

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