CWE-641: Improper Restriction of Names for Files and Other Resources

BaseIncompleteExploit Likelihood: Low

The product constructs the name of a file or other resource using input from an upstream component, but it does not restrict or incorrectly restricts the resulting name.

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Extended Description

This may produce resultant weaknesses. For instance, if the names of these resources contain scripting characters, it is possible that a script may get executed in the client's browser if the application ever displays the name of the resource on a dynamically generated web page. Alternately, if the resources are consumed by some application parser, a specially crafted name can exploit some vulnerability internal to the parser, potentially resulting in execution of arbitrary code on the server machine. The problems will vary based on the context of usage of such malformed resource names and whether vulnerabilities are present in or assumptions are made by the targeted technology that would make code execution possible.

Technical Details

Structure
Simple
Vulnerability Mapping
ALLOWED

Applicable To

Languages
Not Language-Specific
Platforms

Source-backed guidance

Additional facts reviewed against primary or authoritative security sources.

Verify controls for CWE-641 with SSDF evidence

Use NIST SSDF verification and vulnerability-response practices to detect CWE-641, Improper Restriction of Names for Files and Other Resources, throughout the product lifecycle. Derive review questions, static or dynamic checks, and negative tests from the CWE's causal behavior; define the components and lifecycle stages each check covers; and retain findings with enough evidence to distinguish the root cause from symptoms and impacts. Track escapes and false negatives, then improve the verification plan after every confirmed occurrence.

NIST SP 800-218 Secure Software Development Framework — National Institute of Standards and Technology

Address Improper Restriction of Names for Files and Other Resources during Architecture and Design

MITRE associates mitigation with Architecture and Design; recorded impacts include Execute Unauthorized Code or Commands, Read Application Data, and DoS: Crash, Exit, or Restart; related weaknesses include CWE-99. Use these source-defined anchors to turn CWE-641 into implementation, review, and verification checks for the affected component.

CWE-641: Improper Restriction of Names for Files and Other Resources — MITRE CWE

Triage CWE-641 against known exploitation evidence

Use CISA's Known Exploited Vulnerabilities catalog to test whether a vulnerability mapped to CWE-641, Improper Restriction of Names for Files and Other Resources, has evidence of exploitation in the wild. Confirm the CVE-to-CWE root-cause mapping independently before attaching the example, then capture the affected product, required action, and remediation deadline. A missing KEV match is not evidence that the weakness is unexploited, and a KEV entry must not be generalized to every occurrence of this CWE.

Known Exploited Vulnerabilities Catalog — Cybersecurity and Infrastructure Security Agency

Apply precise root-cause mapping to CWE-641

Apply MITRE's full root-cause mapping guidance when using CWE-641, Improper Restriction of Names for Files and Other Resources. Separate weakness language from attacker prerequisites and technical impact, check the entry's abstraction and vulnerability-mapping notes, and prefer the most specific Base or Variant supported by the evidence. Record the rejected alternatives and require an independent review before the mapping is used for remediation trends or program metrics.

CVE to CWE Root Cause Mapping Guidance — MITRE CWE

Validate CWE-641 with root-cause mapping checks

Apply MITRE's root-cause mapping quick tips to CWE-641, Improper Restriction of Names for Files and Other Resources. Confirm the finding describes the causal weakness rather than an impact or attack pattern, compare the abstraction and mapping notes with plausible alternatives, and have a second reviewer challenge the selection. Preserve the evidence and reasoning so recurring defects can be measured against one consistent identifier.

CVE to CWE Root Cause Mapping Quick Tips — MITRE CWE

Frequently Asked Questions

What is CWE-641: Improper Restriction of Names for Files and Other Resources?+

CWE-641: Improper Restriction of Names for Files and Other Resources is a Common Weakness Enumeration (CWE) entry maintained by MITRE. The product constructs the name of a file or other resource using input from an upstream component, but it does not restrict or incorrectly restricts the resulting name. This may produce resultant weaknesses. For instance, if the names of these resources contain scripting characters, it is possible that a script may get executed in the client's browser if the application ever displays the name of the resource on a dynamically generated web page. Alternately, if the resources are consumed by some application parser, a specially crafted name can exploit some vulnerability internal to the parser, potentially resulting in execution of arbitrary code on the server machine. The problems will vary based on the context of usage of such malformed resource names and whether vulnerabilities are present in or assumptions are made by the targeted technology that would make code execution possible.

What are the security consequences of Improper Restriction of Names for Files and Other Resources?+

If exploited, CWE-641 (Improper Restriction of Names for Files and Other Resources) it can compromise Integrity, Confidentiality and Availability, leading to outcomes such as Execute Unauthorized Code or Commands, Read Application Data and DoS: Crash, Exit, or Restart.

How do you prevent or mitigate Improper Restriction of Names for Files and Other Resources?+

Recommended mitigations for CWE-641 include: 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. 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.

Which programming languages are affected by Improper Restriction of Names for Files and Other Resources?+

CWE-641 commonly affects Not Language-Specific. Note that weaknesses are often language-agnostic patterns, so secure coding practices apply broadly.

What is the difference between a CWE and a CVE?+

A CWE (Common Weakness Enumeration) like CWE-641 describes a category of software weakness — the underlying flaw type. A CVE (Common Vulnerabilities and Exposures) identifies a specific, real-world vulnerability in a particular product. In short, a CWE is the kind of mistake, and a CVE is an instance of that mistake being found in software.

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