What’s Vulnerable › Vulnerabilities

CVE-2026-107719: fast-jwt: Verifier cache accepts expired JWTs without iat.

• Severity: medium (CVSS 4.2 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-10-08 · updated 2026-10-09
• Weakness: CWE-613

Description

fast-jwt provides fast JSON Web Token (JWT) implementation. Prior to 6.3.4, the fast-jwt createVerifier cache can continue accepting a previously valid, signed JWT after its exp time when caching is enabled and the token has exp but no iat. In src/verifier.js, cacheSet derives the exp cache deadline only when iat is present, so the cache falls back to cacheTTL, and a later cache hit returns the saved payload before verifyToken rechecks expiration. An attacker who can replay the same cached bearer token can extend access until the cache entry expires, but cannot forge a token through this issue. This issue is fixed in version 6.3.4.

Affected products

• nearform fast-jwt: before 6.3.4

References

• https://github.com/nearform/fast-jwt/commit/fc1ddbbe5ce38066ba2cea0b0ce0233932757167
• https://github.com/nearform/fast-jwt/releases/tag/v6.3.4
• https://github.com/nearform/fast-jwt/security/advisories/GHSA-x937-hj6v-793p
• https://github.com/nearform/fast-jwt/security/advisories/GHSA-x937-hj6v-793p

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