CVE-2026-31808 file-type affected by infinite loop in ASF parser on malformed input with zero-size sub-header
An attacker can cause a denial of service by providing a malformed ASF file that triggers an infinite loop in the file-type library.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-31808?
CVE-2026-31808 is a medium-severity denial of service vulnerability in sindresorhus file-type, published on 10 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Weakness: CWE-835
Which versions are affected by CVE-2026-31808?
2 open source packages ship an affected version, including file-type. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
file-type npm | From 13.0.0 | 21.3.1 |
file-type npm | From 13.0.0 | 21.3.1 |
Products include Sindresorhus File-Type.
How do I fix CVE-2026-31808?
Upgrade file-type to 21.3.1 or later.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-31808 being exploited?
There is no known exploitation of CVE-2026-31808 in the wild and no public exploit code.
Other vulnerabilities in sindresorhus file-type
Sources
Also known as CLSA-2026-1781744121, CLSA-2026-1791199964, GHSA-5v7r-6r5c-r473, MINI-48vg-6499-v62v, MINI-5p46-x4hr-j3g4, MINI-8pwr-phwr-rfgv and 8 more.