Vulnerability in Nearform Fast-Jwt
CVE-2026-107721
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 5.9 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:N.
EPSS exploit prediction
No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.
Affected products
- Nearform Fast-Jwt — versions < 6.3.0
Weakness classification (CWE)
References
Frequently asked questions
- What is CVE-2026-107721?
- CVE-2026-107721 is a medium-severity vulnerability in Nearform Fast-Jwt, classified under Insufficient Session Expiration. CVSS score: 5.9/10. Published 2026-10-08.
- How severe is CVE-2026-107721?
- Medium severity. CVSS v3 base score is 5.9 out of 10.