Vulnerability · Published Oct 8, 2026 · Assigned by GitHub_M

CVE-2026-107721fast-jwt clockTolerance: Infinity silently bypasses both exp and nbf validation (and persists in the verifier cache)

Medium 5.9

In plain English

A medium-severity security flaw in fast-jwt from nearform. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 28% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)5.9Medium

Exploit odds (30 days)0.3%top 72.2% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official description

fast-jwt provides fast JSON Web Token (JWT) implementation. Prior to 6.3.0, fast-jwt createVerifier accepts Infinity for clockTolerance because its option validation checks type and negativity but not finiteness. In validateClaimDateValue, infinite positive and negative modifiers make exp and nbf comparisons always pass, allowing expired or not-yet-active tokens to be accepted. The verifier cache also derives infinite bounds, so entries created under this configuration can remain valid until eviction. Exploitation requires an application administrator or equivalent configuration path to set clockTolerance to Infinity. This issue is fixed in version 6.3.0.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
npm	fast-jwt	6.3.0	GHSA-687g-22h4-j4w4

Affected products (as reported)

Vendor	Product	Versions
nearform	fast-jwt	< 6.3.0

Weakness: CWE-613, CWE-682 · Vector: CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:N

References

https://github.com/nearform/fast-jwt/security/advisories/GHSA-687g-22h4-j4w4 x_refsource_CONFIRM
https://github.com/nearform/fast-jwt/commit/c0fb5b88b4c88ff2bdd194ca2c713599ad9e38b6 x_refsource_MISC
https://github.com/nearform/fast-jwt/releases/tag/v6.3.0 x_refsource_MISC