CVE-2026-31808
file-type affected by infinite loop in ASF parser on malformed input with zero-size sub-header
Impact
### 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
Affected packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| npm | file-type | >= 13.0.0, < 21.3.1 | 21.3.1 |
Affected products
| Vendor | Product | Affected versions |
|---|---|---|
| Sindresorhus | File-Type | from 13.0.0 before 21.3.1 |
Weakness classification
References
- NVD record
- CVE.org record
- GitHub advisory
- https://github.com/sindresorhus/file-type/commit/319abf871b50ba2fa221b4a7050059f1ae096f4f
- https://github.com/sindresorhus/file-type/security/advisories/GHSA-5v7r-6r5c-r473
- https://github.com/advisories/GHSA-5v7r-6r5c-r473
- https://nvd.nist.gov/vuln/detail/CVE-2026-31808