CVE-2026-31808: Sindresorhus File-Type

Medium severity, CVSS 5.3. EPSS: 0.4% chance of exploitation in the next 30 days.

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)

Published 2026-03-10. Last modified 2026-06-17.