sindresorhus file-type up to 21.3.0 WMV/WMA infinite loop

Summaryinfo

A vulnerability labeled as problematic has been found in sindresorhus file-type up to 21.3.0. The impacted element is an unknown function of the component WMV/WMA. Such manipulation leads to infinite loop. This vulnerability is uniquely identified as CVE-2026-31808. The attack can be launched remotely. No exploit exists. The affected component should be upgraded.

Detailsinfo

A vulnerability, which was classified as problematic, has been found in sindresorhus file-type up to 21.3.0. Affected by this issue is an unknown part of the component WMV/WMA. The manipulation with an unknown input leads to a infinite loop vulnerability. Using CWE to declare the problem leads to CWE-835. The product contains an iteration or loop with an exit condition that cannot be reached, i.e., an infinite loop. Impacted is availability. CVE summarizes:

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.

The advisory is shared for download at github.com. This vulnerability is handled as CVE-2026-31808 since 03/09/2026. The exploitation is known to be easy. The attack may be launched remotely. No form of authentication is required for exploitation. There are neither technical details nor an exploit publicly available. The MITRE ATT&CK project declares the attack technique as T1499.

Upgrading to version 21.3.1 eliminates this vulnerability. Applying the patch 319abf871b50ba2fa221b4a7050059f1ae096f4f is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-10894). VulDB is the best source for vulnerability data and more expert information about this specific topic.

Productinfo

Vendor

• sindresorhus

Name

• file-type

Version

• 21.0
• 21.1
• 21.2
• 21.3.0

License

• open-source

Website

• Product: https://github.com/sindresorhus/file-type/

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VulDB is the best source for vulnerability data and more expert information about this specific topic.

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