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

  • CVE-2006-7135

    extract issue enables file inclusion

  • CVE-2006-7079

    Chain: extract used for register_globals compatibility layer, enables path traversal (CWE-22)

  • CVE-2007-0649

    extract() buried in include files makes post-disclosure analysis confusing; original report had seemed incorrect.

  • CVE-2006-6661

    extract() enables static code injection

  • CVE-2006-2828

    import_request_variables() buried in include files makes post-disclosure analysis confusing

  • CVE-2009-0422

    Chain: Dynamic variable evaluation allows resultant remote file inclusion and path traversal.

  • CVE-2007-2431

    Chain: dynamic variable evaluation in PHP program used to modify critical, unexpected $_SERVER variable for resultant XSS.

  • CVE-2006-4904

    Chain: dynamic variable evaluation in PHP program used to conduct remote file inclusion.

How attackers exploit it

Step-by-step attacker path

  1. 1

    Identify a code path that handles untrusted input without validation.

  2. 2

    Craft a payload that exercises the unsafe behavior — injection, traversal, overflow, or logic abuse.

  3. 3

    Deliver the payload through a normal request and observe the application's reaction.

  4. 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.

Vulnerable 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));
Secure code example

Secure pseudo

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

SAST High

Run static analysis (SAST) on the codebase looking for the unsafe pattern in the data flow.

DAST Moderate

Run dynamic application security testing against the live endpoint.

Runtime Moderate

Watch runtime logs for unusual exception traces, malformed input, or authorization bypass attempts.

Code review Moderate

Code review: flag any new code that handles input from this surface without using the validated framework helpers.

Plexicus auto-fix

Plexicus auto-detects CWE-914 and opens a fix PR in under 60 seconds.

Codex Remedium scans every commit, identifies this exact weakness, and ships a reviewer-ready pull request with the patch. No tickets. No hand-offs.

Get a demo Try Plexicus free
Frequently asked questions

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.…

Resources

Further reading

Ready when you are

Don't Let Security
Weigh You Down.

Stop choosing between AI velocity and security debt. Plexicus is the only platform that runs Vibe Coding Security and ASPM in parallel — one workflow, every codebase.

Get started free Book a demo