CVE-2026-35041: medium-severity vulnerability in nearform fast-jwt
ReDoS in fast-jwt when using RegExp in allowed* leading to CPU exhaustion during token verification
Published
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13Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 4.2epss 0.3%
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.
CVSS:3.1/AV:N/AC:H/PR:H/UI:R/S:U/C:N/I:N/A:H
Affected products
nearform · fast-jwtRelated CVEs — nearform fast-jwt
In the same product, most dangerous first.
CVE-2023-48223MEDIUMfast-jwt JWT Algorithm ConfusionEPSS 0.7%CVE-2025-30144MEDIUMFast-JWT Improperly Validates iss ClaimsEPSS 0.6%CVE-2026-107723HIGHfast-jwt : Silent claim-validator bypass when JWT payload is a JSON arrayEPSS 0.5%CVE-2026-35040MEDIUMfast-jwt: Stateful RegExp (/g or /y) causes non-deterministic allowed-claim validation (logical DoS)EPSS 0.4%CVE-2026-107722CRITICALfast-jwt: Incomplete patch of CVE-2026-34950: Non-whitespace key-prefix re-enables RSA→HS256 algorithm confusionEPSS 0.4%CVE-2026-107721MEDIUMfast-jwt clockTolerance: Infinity silently bypasses both exp and nbf validation (and persists in the verifier cache)EPSS 0.3%