What’s Vulnerable › Vulnerabilities

CVE-2026-31808: file-type affected by infinite loop in ASF parser on malformed input with zero-size sub-header

• Severity: medium (CVSS 5.3 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-03-10 · updated 2026-06-17
• Weakness: CWE-835

Description

file-type detects the file type of a file, stream, or data. Prior to 21.3.1, 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. Fixed in version 21.3.1.

Affected products

• sindresorhus file-type: from 13.0.0 before 21.3.1 — fixed in 21.3.1

How to fix

Upgrade to a fixed version: sindresorhus file-type 21.3.1. Check the vendor advisory for mitigations.

References

• https://github.com/sindresorhus/file-type/commit/319abf871b50ba2fa221b4a7050059f1ae096f4f
• https://github.com/sindresorhus/file-type/security/advisories/GHSA-5v7r-6r5c-r473

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