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.
Published: 2026-04-09
Score: 4.2 Medium
EPSS: n/a
KEV: No
Impact: n/a
Action: n/a
AI Analysis

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Remediation

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Tracking

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Advisories
Source ID Title
Github GHSA Github GHSA GHSA-cjw9-ghj4-fwxf fast-jwt has a ReDoS when using RegExp in allowed* leading to CPU exhaustion during token verification
History

Thu, 09 Apr 2026 17:15:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'poc', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Thu, 09 Apr 2026 15:30:00 +0000

Type Values Removed Values Added
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.
Title ReDoS in fast-jwt when using RegExp in allowed* leading to CPU exhaustion during token verification
Weaknesses CWE-1333
References
Metrics cvssV3_1

{'score': 4.2, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:H/UI:R/S:U/C:N/I:N/A:H'}


Subscriptions

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cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-04-09T16:15:25.352Z

Reserved: 2026-03-31T21:06:06.428Z

Link: CVE-2026-35041

cve-icon Vulnrichment

Updated: 2026-04-09T16:14:24.545Z

cve-icon NVD

Status : Received

Published: 2026-04-09T16:16:27.383

Modified: 2026-04-09T17:16:25.473

Link: CVE-2026-35041

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

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Weaknesses