Description
fast-jwt provides fast JSON Web Token (JWT) implementation. From 5.0.0 to 6.2.0, a denial-of-service condition exists in fast-jwt when the allowedAud verification option is configured using a regular expression. Because the aud claim is attacker-controlled and the library evaluates it against the supplied RegExp, a crafted JWT can trigger catastrophic backtracking in the JavaScript regex engine, resulting in significant CPU consumption during verification. This vulnerability is fixed in 6.2.1.
Affected products
nearform: fast-jwt
References5
- github.com/nearform/fast-jwt/security/advisories/GHSA-cjw9-ghj4… ExploitMitigationVendor Advisory
- github.com/nearform/fast-jwt/security/advisories/GHSA-cjw9-ghj4… ExploitMitigationVendor Advisory
- github.com/nearform/fast-jwt/commit/b0be0ca161593836a153d5180ca… Patch
- github.com/nearform/fast-jwt/pull/595 Issue TrackingPatch
- github.com/nearform/fast-jwt/releases/tag/v6.2.1 ProductRelease Notes
Metrics
- CVSS 3.1
-
6.5
MEDIUM
Score source: NVD
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H - EPSS — exploit probability
- 0% percentile: 20 · as of 12 November 2026
- CWE
- CWE-1333
Could this be exploited in your environment?
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