CVE-2026-35041
ReDoS in fast-jwt when using RegExp in allowed* leading to CPU exhaustion during token verification
CVSS Score
4.2
EPSS Score
0.0%
EPSS Percentile
0th
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.
| CWE | CWE-1333 |
| Vendor | nearform |
| Product | fast-jwt |
| Published | Apr 9, 2026 |
| Last Updated | Apr 9, 2026 |
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CVSS v3 Breakdown
CVSS:3.1/AV:N/AC:H/PR:H/UI:R/S:U/C:N/I:N/A:H Attack Vector
Network
Attack Complexity
High
Privileges Required
High
User Interaction
Required
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High
Affected Versions
nearform / fast-jwt
>= 5.0.0, < 6.2.1
References
github.com: https://github.com/nearform/fast-jwt/security/advisories/GHSA-cjw9-ghj4-fwxf github.com: https://github.com/nearform/fast-jwt/pull/595 github.com: https://github.com/nearform/fast-jwt/commit/b0be0ca161593836a153d5180ca5358ad9b5de94 github.com: https://github.com/nearform/fast-jwt/releases/tag/v6.2.1