CVE-2026-35041
ReDoS in fast-jwt when using RegExp in allowed* leading to CPU exhaustion during token verification
- State
- Published
- Severity
- 4.2 Medium
- Published
- Apr 9, 2026
- Updated
- Apr 9, 2026
- Reserved
- Mar 31, 2026
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 3.1 | 4.2 Medium | CVSS:3.1/AV:N/AC:H/PR:H/UI:R/S:U/C:N/I:N/A:H | GitHub_M |
Weaknesses
- CWE-1333 Inefficient Regular Expression Complexity
Affected Products
| Product | Versions |
|---|---|
fast-jwtnearform |
|
References
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