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

Applicable To

Languages
Not Language-Specific
Platforms

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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