CWE - CWE-914: Improper Control of Dynamically-Identified Variables (4.19.1)
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    CWE-914: Improper Control of Dynamically-Identified Variables

    Weakness ID: 914
    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 does not properly restrict reading from or writing to dynamically-identified variables.
    + Extended Description
    Many languages offer powerful features that allow the programmer to access arbitrary variables that are specified by an input string. While these features can offer significant flexibility and reduce development time, they can be extremely dangerous if attackers can modify unintended variables that have security implications.
    + 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.
    Impact Details

    Modify Application Data

    		Scope: Integrity

    An attacker could modify sensitive data or program variables.

    Execute Unauthorized Code or Commands

    		Scope: Integrity

    Varies by Context; Alter Execution Logic

    		Scope: Other, Integrity

    + Potential Mitigations
    Phase(s) Mitigation

    Implementation

    Strategy: Input Validation

    For any externally-influenced input, check the input against an allowlist of internal program variables that are allowed to be modified.

    Implementation; Architecture and Design

    Strategy: Refactoring

    Refactor the code so that internal program variables do not need to be dynamically identified.
    + Relationships
    Section Help 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" (View-1000)
    Nature Type ID Name
    ChildOf Class 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. 99 Improper Control of Resource Identifiers ('Resource Injection')
    ChildOf Class 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. 913 Improper Control of Dynamically-Managed Code Resources
    ParentOf Variant Variant - a weakness that is linked to a certain type of product, typically involving a specific language or technology. More specific than a Base weakness. Variant level weaknesses typically describe issues in terms of 3 to 5 of the following dimensions: behavior, property, technology, language, and resource. 621 Variable Extraction Error
    ParentOf Variant Variant - a weakness that is linked to a certain type of product, typically involving a specific language or technology. More specific than a Base weakness. Variant level weaknesses typically describe issues in terms of 3 to 5 of the following dimensions: behavior, property, technology, language, and resource. 627 Dynamic Variable Evaluation
    + Relevant to the view "Software Development" (View-699)
    Nature Type ID Name
    MemberOf Category Category - a CWE entry that contains a set of other entries that share a common characteristic. 399 Resource Management Errors
    + 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.
    Phase Note
    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: Not Language-Specific (Undetermined Prevalence)

    Class: Interpreted (Undetermined Prevalence)

    + Demonstrative Examples

    Example 1


    This code uses the credentials sent in a POST request to login a user.

    (bad code)
    Example Language: PHP 
    //Log user in, and set $isAdmin to true if user is an administrator

    function login($user,$pass){
    $query = buildQuery($user,$pass);
    mysql_query($query);
    if(getUserRole($user) == "Admin"){
    $isAdmin = true;
    }
    }

    $isAdmin = false;
    extract($_POST);
    login(mysql_real_escape_string($user),mysql_real_escape_string($pass));

    The call to extract() will overwrite the existing values of any variables defined previously, in this case $isAdmin. An attacker can send a POST request with an unexpected third value "isAdmin" equal to "true", thus gaining Admin privileges.



    + Selected Observed Examples

    Note: this is a curated list of examples for users to understand the variety of ways in which this weakness can be introduced. It is not a complete list of all CVEs that are related to this CWE entry.

    Reference Description
    extract issue enables file inclusion
    Chain: extract used for register_globals compatibility layer, enables path traversal (CWE-22)
    extract() buried in include files makes post-disclosure analysis confusing; original report had seemed incorrect.
    extract() enables static code injection
    import_request_variables() buried in include files makes post-disclosure analysis confusing
    Chain: Dynamic variable evaluation allows resultant remote file inclusion and path traversal.
    Chain: dynamic variable evaluation in PHP program used to modify critical, unexpected $_SERVER variable for resultant XSS.
    Chain: dynamic variable evaluation in PHP program used to conduct remote file inclusion.
    Dynamic variable evaluation in mail program allows reading and modifying attachments and preferences of other users.
    + Weakness Ordinalities
    Ordinality Description
    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.
    Nature Type ID Name
    MemberOf CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. 1409 Comprehensive Categorization: Injection
    + Vulnerability Mapping Notes
    Usage ALLOWED
    (this CWE ID 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.
    + Content History
    + Submissions
    Submission Date Submitter Organization
    2013-01-26
    (CWE 2.4, 2013-02-21)     		CWE Content Team MITRE
    + Modifications
    Modification Date Modifier Organization
    2025-12-11
    (CWE 4.19, 2025-12-11)     		CWE Content Team MITRE
    updated Applicable_Platforms
    2023-10-26 CWE Content Team MITRE
    updated Observed_Examples
    2023-06-29 CWE Content Team MITRE
    updated Mapping_Notes
    2023-04-27 CWE Content Team MITRE
    updated Relationships, Time_of_Introduction
    2023-01-31 CWE Content Team MITRE
    updated Description
    2020-06-25 CWE Content Team MITRE
    updated Potential_Mitigations
    2020-02-24 CWE Content Team MITRE
    updated Relationships
    2017-01-19 CWE Content Team MITRE
    updated Relationships
    Page Last Updated: January 21, 2026