EUVD-2026-20899
GHSA-cjw9-ghj4-fwxf
CVSS Vector
CVSS:3.1/AV:N/AC:H/PR:H/UI:R/S:U/C:N/I:N/A:H
Lifecycle Timeline
4Description
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.
Analysis
Denial of service in fast-jwt 5.0.0 through 6.2.0 allows authenticated remote attackers with user interaction to cause significant CPU consumption via crafted JWT tokens that trigger catastrophic backtracking in regular expression evaluation when the allowedAud verification option is configured with a regex pattern. The vulnerability exploits attacker-controlled aud claims evaluated against user-supplied regexes, resulting in ReDoS (regular expression denial of service). …
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