Run static analysis (SAST) on the codebase looking for the unsafe pattern in the data flow.
CWE-914 Base Incomplete
Improper Control of Dynamically-Identified Variables
This vulnerability occurs when an application fails to properly secure access to variables whose names are determined at runtime, allowing attackers to read or modify data they shouldn't have access…
Definition
What is CWE-914?
This vulnerability occurs when an application fails to properly secure access to variables whose names are determined at runtime, allowing attackers to read or modify data they shouldn't have access to.
Many programming languages provide dynamic variable access features—like using string inputs to directly reference variable names—which can accelerate development by offering great flexibility. However, when these features accept unvalidated user input, they create a dangerous pathway for attackers to manipulate critical variables controlling authentication, authorization, or application logic.
This risk is especially severe because attackers can often guess or discover variable names with security significance, such as those holding user permissions, configuration flags, or sensitive data. To prevent this, developers must avoid using dynamic variable access with user-controlled input entirely, or implement strict allow-list validation to restrict which variable names can be referenced through these mechanisms.
Real-world impact
Real-world CVEs caused by CWE-914
-
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.
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extract() enables static code injection
-
import_request_variables() buried in include files makes post-disclosure analysis confusing
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Chain: Dynamic variable evaluation allows resultant remote file inclusion and path traversal.
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Chain: dynamic variable evaluation in PHP program used to modify critical, unexpected $_SERVER variable for resultant XSS.
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Chain: dynamic variable evaluation in PHP program used to conduct remote file inclusion.
How attackers exploit it
Step-by-step attacker path
- 1
Identify a code path that handles untrusted input without validation.
- 2
Craft a payload that exercises the unsafe behavior — injection, traversal, overflow, or logic abuse.
- 3
Deliver the payload through a normal request and observe the application's reaction.
- 4
Iterate until the response leaks data, executes attacker code, or escalates privileges.
Vulnerable code example
Vulnerable PHP
This code uses the credentials sent in a POST request to login a user.
```
//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)); Secure code example
Secure pseudo
// Validate, sanitize, or use a safe API before reaching the sink.
function handleRequest(input) {
const safe = validateAndEscape(input);
return executeWithGuards(safe);
} What changed: the unsafe sink is replaced (or the input is validated/escaped) so the same payload no longer triggers the weakness.
Prevention checklist
How to prevent CWE-914
- Implementation 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 Refactor the code so that internal program variables do not need to be dynamically identified.
Detection signals
How to detect CWE-914
Run dynamic application security testing against the live endpoint.
Watch runtime logs for unusual exception traces, malformed input, or authorization bypass attempts.
Code review: flag any new code that handles input from this surface without using the validated framework helpers.
CWE-914
Don't catalog this weakness. Prove it's reachable.
Plexicus turns CWE catalogs into evidence: every CWE-pattern is matched against your real code graph, reach is proven on a sandbox clone, and verified findings ship as reviewed PRs.
Frequently asked questions What is CWE-914?
How serious is CWE-914?
What languages or platforms are affected by CWE-914?
How can I prevent CWE-914?
How does Plexicus detect and fix CWE-914?
Where can I learn more about CWE-914?
Frequently asked questions
What is CWE-914?
This vulnerability occurs when an application fails to properly secure access to variables whose names are determined at runtime, allowing attackers to read or modify data they shouldn't have access to.
How serious is CWE-914?
MITRE has not published a likelihood-of-exploit rating for this weakness. Treat it as medium-impact until your threat model proves otherwise.
What languages or platforms are affected by CWE-914?
MITRE has not specified affected platforms for this CWE — it can apply across most application stacks.
How can I prevent CWE-914?
For any externally-influenced input, check the input against an allowlist of internal program variables that are allowed to be modified. Refactor the code so that internal program variables do not need to be dynamically identified.
How does Plexicus detect and fix CWE-914?
Plexicus's SAST engine matches the data-flow signature for CWE-914 on every commit. When a match is found, our Codex Remedium agent opens a fix PR with the corrected code, tests, and a one-line summary for the reviewer.
Where can I learn more about CWE-914?
MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/914.html. You can also reference OWASP and NIST documentation for adjacent guidance.
Related weaknesses
Weaknesses related to CWE-914
CWE-99 Parent
Improper Control of Resource Identifiers ('Resource Injection')
This vulnerability occurs when an application accepts user input as a resource identifier (like a file path or port number) without proper…
CWE-641 Sibling
Improper Restriction of Names for Files and Other Resources
This vulnerability occurs when an application creates file or resource names using unvalidated user input, failing to properly limit what…
CWE-694 Sibling
Use of Multiple Resources with Duplicate Identifier
This vulnerability occurs when a system uses multiple resources that can share the same identifier, even though the application logic…
CWE-621 Child
Variable Extraction Error
This vulnerability occurs when an application uses unvalidated external input to dynamically select which variables to populate with data.…
CWE-627 Child
Dynamic Variable Evaluation
This vulnerability occurs when an application allows user input to directly determine which variable or function name is used at runtime.…
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