GHSA-CJW9-GHJ4-FWXF fast-jwt has a ReDoS when using RegExp in allowed* leading to CPU exhaustion during token verification

⚠️ IMPORTANT CLARIFICATIONS Affected Configurations This vulnerability ONLY affects applications that: - Use RegExp objects not strings in the allowedAud, allowedIss, allowedSub, allowedJti, or allowedNonce options - Configure patterns susceptible to catastrophic backtracking - Example: allowedAud...

fast-jwt: Stateful RegExp (/g or /y) causes non-deterministic allowed-claim validation (logical DoS)

Impact Using certain modifiers on RegExp objects in the allowedAud, allowedIss, allowedSub, allowedJti, or allowedNonce options in verify functions can cause certain unintended behaviours. This is because some modifiers are stateful and will cause failures in every second verification attempt...

CVE-2026-35040

CVE-2026-35040 affects the fast-jwt library prior to version 6.2.1. The issue involves stateful RegExp modifiers /g and /y used in allowedAud, allowedIss, allowedSub, allowedJti, or allowedNonce verify options, which can cause 50% of valid authentication attempts to fail in an alternating pattern...