CVE-2026-35041
MEDIUMReDoS in fast-jwt when using RegExp in allowed* leading to CPU exhaustion during token verification
Title source: cnaDescription
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.
References (4)
Core 4
Core References
X_Refsource_Confirm x_refsource_confirm
https://github.com/nearform/fast-jwt/security/advisories/GHSA-cjw9-ghj4-fwxf
X_Refsource_Misc x_refsource_misc
https://github.com/nearform/fast-jwt/pull/595
X_Refsource_Misc x_refsource_misc
https://github.com/nearform/fast-jwt/commit/b0be0ca161593836a153d5180ca5358ad9b5de94
X_Refsource_Misc x_refsource_misc
https://github.com/nearform/fast-jwt/releases/tag/v6.2.1
Scores
CVSS v3
4.2
EPSS
0.0026
EPSS Percentile
17.3%
Attack Vector
NETWORK
CVSS:3.1/AV:N/AC:H/PR:H/UI:R/S:U/C:N/I:N/A:H
CISA SSVC
Vulnrichment
Exploitation
poc
Automatable
no
Technical Impact
partial
Details
CWE
CWE-1333
Status
published
Products (3)
nearform/fast-jwt
5.0.0 - 6.2.1
nearform/fast-jwt
>= 5.0.0, < 6.2.1
npm/fast-jwt
5.0.0 - 6.2.1npm
Published
Apr 09, 2026
Tracked Since
Apr 09, 2026