CWE - CWE-766: Critical Data Element Declared Public (4.16)

Weakness ID: 766

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

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Description

The product declares a critical variable, field, or member to be public when intended security policy requires it to be private.

Extended Description

This issue makes it more difficult to maintain the product, which indirectly affects security by making it more difficult or time-consuming to find and/or fix vulnerabilities. It also might make it easier to introduce vulnerabilities.

Common Consequences

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

Scope	Impact	Likelihood
Integrity Confidentiality	Technical Impact: Read Application Data; Modify Application Data Making a critical variable public allows anyone with access to the object in which the variable is contained to alter or read the value.
Other	Technical Impact: Reduce Maintainability

Potential Mitigations

Phase: Implementation

Data should be private, static, and final whenever possible. This will assure that your code is protected by instantiating early, preventing access, and preventing tampering.

Relationships

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

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

Nature	Type	ID	Name
ChildOf	Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource.	732	Incorrect Permission Assignment for Critical Resource
ChildOf	Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource.	1061	Insufficient Encapsulation

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

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

Modes Of Introduction

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

Phase	Note
Implementation

Applicable Platforms

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

Languages

C++ (Undetermined Prevalence)

C# (Undetermined Prevalence)

Java (Undetermined Prevalence)

Demonstrative Examples

Example 1

The following example declares a critical variable public, making it accessible to anyone with access to the object in which it is contained.

(bad code)

Example Language: C++

public: char* password;

Instead, the critical data should be declared private.

(good code)

Example Language: C++

private: char* password;

Even though this example declares the password to be private, there are other possible issues with this implementation, such as the possibility of recovering the password from process memory (CWE-257).

Example 2

The following example shows a basic user account class that includes member variables for the username and password as well as a public constructor for the class and a public method to authorize access to the user account.

(bad code)

Example Language: C++

#define MAX_PASSWORD_LENGTH 15
#define MAX_USERNAME_LENGTH 15

class UserAccount
{

public:

UserAccount(char *username, char *password)
{

if ((strlen(username) > MAX_USERNAME_LENGTH) ||
(strlen(password) > MAX_PASSWORD_LENGTH)) {

ExitError("Invalid username or password");

}
strcpy(this->username, username);
strcpy(this->password, password);

}

int authorizeAccess(char *username, char *password)
{

if ((strlen(username) > MAX_USERNAME_LENGTH) ||
(strlen(password) > MAX_PASSWORD_LENGTH)) {

ExitError("Invalid username or password");

}
// if the username and password in the input parameters are equal to

// the username and password of this account class then authorize access
if (strcmp(this->username, username) ||
strcmp(this->password, password))

return 0;

// otherwise do not authorize access
else

return 1;

}

char username[MAX_USERNAME_LENGTH+1];
char password[MAX_PASSWORD_LENGTH+1];

};

However, the member variables username and password are declared public and therefore will allow access and changes to the member variables to anyone with access to the object. These member variables should be declared private as shown below to prevent unauthorized access and changes.

(good code)

Example Language: C++

class UserAccount
{
public:

...

private:

char username[MAX_USERNAME_LENGTH+1];
char password[MAX_PASSWORD_LENGTH+1];

};

Observed Examples

Reference	Description
CVE-2010-3860	variables declared public allow remote read of system properties such as user name and home directory.

Weakness Ordinalities

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

Detection Methods

Automated Static Analysis

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

Effectiveness: High

Memberships

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

Nature	Type	ID	Name
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	849	The CERT Oracle Secure Coding Standard for Java (2011) Chapter 6 - Object Orientation (OBJ)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1002	SFP Secondary Cluster: Unexpected Entry Points
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1130	CISQ Quality Measures (2016) - Maintainability
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1139	SEI CERT Oracle Secure Coding Standard for Java - Guidelines 05. Object Orientation (OBJ)
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1412	Comprehensive Categorization: Poor Coding Practices

Vulnerability Mapping Notes

Usage: ALLOWED

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

Reason: Acceptable-Use

Rationale:

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

Comments:

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

Taxonomy Mappings

Mapped Taxonomy Name	Node ID	Mapped Node Name
CLASP		Failure to protect stored data from modification
The CERT Oracle Secure Coding Standard for Java (2011)	OBJ01-J	Declare data members as private and provide accessible wrapper methods
Software Fault Patterns	SFP28	Unexpected access points
OMG ASCMM	ASCMM-MNT-15

References

[REF-960] Object Management Group (OMG). "Automated Source Code Maintainability Measure (ASCMM)". ASCMM-MNT-15. 2016-01. <https://www.omg.org/spec/ASCMM/>. URL validated: 2023-04-07.

Content History

Submissions
Submission Date	Submitter	Organization
2009-03-03 (CWE 1.4, 2009-05-27)	CWE Content Team	MITRE
2009-03-03 (CWE 1.4, 2009-05-27)
Modifications
Modification Date	Modifier	Organization
2009-12-28	CWE Content Team	MITRE
2009-12-28	updated Demonstrative_Examples
2010-12-13	CWE Content Team	MITRE
2010-12-13	updated Observed_Examples
2011-06-01	CWE Content Team	MITRE
2011-06-01	updated Common_Consequences, Relationships, Taxonomy_Mappings
2012-05-11	CWE Content Team	MITRE
2012-05-11	updated Relationships
2014-07-30	CWE Content Team	MITRE
2014-07-30	updated Relationships, Taxonomy_Mappings
2017-11-08	CWE Content Team	MITRE
2017-11-08	updated Likelihood_of_Exploit, Relationships
2019-01-03	CWE Content Team	MITRE
2019-01-03	updated Common_Consequences, Description, Name, References, Relationships, Taxonomy_Mappings, Weakness_Ordinalities
2020-02-24	CWE Content Team	MITRE
2020-02-24	updated Relationships
2023-01-31	CWE Content Team	MITRE
2023-01-31	updated Description
2023-04-27	CWE Content Team	MITRE
2023-04-27	updated Detection_Factors, References, Relationships, Time_of_Introduction, Type
2023-06-29	CWE Content Team	MITRE
2023-06-29	updated Mapping_Notes, Relationships
2023-10-26	CWE Content Team	MITRE
2023-10-26	updated Observed_Examples
2024-02-29 (CWE 4.14, 2024-02-29)	CWE Content Team	MITRE
2024-02-29 (CWE 4.14, 2024-02-29)	updated Demonstrative_Examples
Previous Entry Names
Change Date	Previous Entry Name
2019-01-03	Critical Variable Declared Public


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Common Weakness Enumeration

CWE-766: Critical Data Element Declared Public

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