In short
- CVE-2026-31808 is a MEDIUM (CVSS 5.3) vulnerability affecting file-type (sindresorhus), file-type.
- Chance of exploitation in the next 30 days (EPSS): 0.37%, higher than 30.9% of all vulnerabilities.
- Fix: update to 21.3.1 or later.
| Package | Affected versions | Patched versions |
|---|
| file-type | ≥ 13.0.0, < 21.3.1
| 21.3.1
|
| file-type npm | ≥ 13.0.0, < 21.3.1
| 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
[email protected]
NVD 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.
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