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file-type affected by infinite loop in ASF parser on malformed input with zero-size sub-header

Moderate severity GitHub Reviewed Published Mar 9, 2026 in sindresorhus/file-type • Updated Mar 10, 2026

Package

npm file-type (npm)

Affected versions

>= 13.0.0, < 21.3.1

Patched versions

21.3.1

Description

Impact

A denial of service vulnerability exists in the ASF (WMV/WMA) file type detection parser. When parsing a crafted input where an ASF sub-header has a size field of zero, the parser enters an infinite loop. The payload value becomes negative (-24), causing tokenizer.ignore(payload) to move the read position backwards, so the same sub-header is read repeatedly forever.

Any application that uses file-type to detect the type of untrusted/attacker-controlled input is affected. An attacker can stall the Node.js event loop with a 55-byte payload.

Patches

Fixed in version 21.3.1. Users should upgrade to >= 21.3.1.

Workarounds

Validate or limit the size of input buffers before passing them to file-type, or run file type detection in a worker thread with a timeout.

References

  • Fix commit: 319abf871b50ba2fa221b4a7050059f1ae096f4f

Reporter

crnkovic@lokvica.com

References

@sindresorhus sindresorhus published to sindresorhus/file-type Mar 9, 2026
Published by the National Vulnerability Database Mar 10, 2026
Published to the GitHub Advisory Database Mar 10, 2026
Reviewed Mar 10, 2026
Last updated Mar 10, 2026

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
Low

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(8th percentile)

Weaknesses

Loop with Unreachable Exit Condition ('Infinite Loop')

The product contains an iteration or loop with an exit condition that cannot be reached, i.e., an infinite loop. Learn more on MITRE.

CVE ID

CVE-2026-31808

GHSA ID

GHSA-5v7r-6r5c-r473

Source code

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