CWE-641 Base Incomplete Low likelihood

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 characters or paths can be used.

Definition

What is CWE-641?

This vulnerability occurs when an application creates file or resource names using unvalidated user input, failing to properly limit what characters or paths can be used.
When an application builds a resource name—like a filename, directory path, or URL—from external input without strict validation, it opens the door to multiple attack vectors. An attacker can inject special characters, path traversal sequences (like `../`), or even script code into the name. If the application later uses that name, say, to include a file on a web page or pass it to a system command, it can trigger unexpected and dangerous behavior. The specific risk depends entirely on how the malformed name is used. For example, if the tainted name is displayed in a web page, it could lead to Cross-Site Scripting (XSS) in a user's browser. If it's processed by a server-side parser or the operating system itself, it could allow path traversal to access sensitive files, cause denial-of-service, or in the worst case, lead to remote code execution by exploiting a vulnerability in the underlying processing component.
Real-world impact

Real-world CVEs caused by CWE-641

No public CVE references are linked to this CWE in MITRE's catalog yet.

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 pseudo

MITRE has not published a code example for this CWE. The pattern below is illustrative — see Resources for canonical references.

Vulnerable pseudo 
// Example pattern — see MITRE for the canonical references.
function handleRequest(input) {
  // Untrusted input flows directly into the sensitive sink.
  return executeUnsafe(input);
}
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-641

  • Architecture and Design Do not allow users to control names of resources used on the server side.
  • Architecture and Design Perform allowlist input validation at entry points and also before consuming the resources. Reject bad file names rather than trying to cleanse them.
  • Architecture and Design Make sure that technologies consuming the resources are not vulnerable (e.g. buffer overflow, format string, etc.) in a way that would allow code execution if the name of the resource is malformed.
Detection signals

How to detect CWE-641

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-641 and opens a fix PR in under 60 seconds.

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Frequently asked questions

Frequently asked questions

What is CWE-641?

This vulnerability occurs when an application creates file or resource names using unvalidated user input, failing to properly limit what characters or paths can be used.

How serious is CWE-641?

MITRE rates the likelihood of exploit as Low — exploitation is uncommon, but the weakness should still be fixed when discovered.

What languages or platforms are affected by CWE-641?

MITRE has not specified affected platforms for this CWE — it can apply across most application stacks.

How can I prevent CWE-641?

Do not allow users to control names of resources used on the server side. Perform allowlist input validation at entry points and also before consuming the resources. Reject bad file names rather than trying to cleanse them.

How does Plexicus detect and fix CWE-641?

Plexicus's SAST engine matches the data-flow signature for CWE-641 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-641?

MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/641.html. You can also reference OWASP and NIST documentation for adjacent guidance.

Related weaknesses

Weaknesses related to CWE-641

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-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-914 Sibling

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…

Resources

Further reading

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