Insufficient Session Expiration Affecting fast-jwt package, versions <6.3.0
Threat Intelligence
Snyk has a proof-of-concept or detailed explanation of how to exploit this vulnerability.
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Start learning- Snyk IDSNYK-JS-FASTJWT-20825053
- published11 Oct 2026
- disclosed8 Oct 2026
- creditAndrew Ridings
Introduced: 8 Oct 2026
NewCVE-2026-107721 (opens in a new tab)How to fix?
Upgrade fast-jwt to version 6.3.0 or higher.
Overview
fast-jwt is a Fast JSON Web Token implementation
Affected versions of this package are vulnerable to Insufficient Session Expiration in src/verifier.js when the clockTimestamp, clockTolerance, or cacheTTL verifier options are set to non-finite values such as Infinity or NaN. The previous validation used a truthy guard (x && ...) and checked only that the value was a non-negative number, so Infinity passed validation and disabled exp/nbf claim enforcement entirely, while NaN bypassed the truthy check and also went undetected. An attacker who can control these verifier options can cause token expiry and not-before checks to be silently skipped, allowing expired or not-yet-valid tokens to be accepted as valid.