VulnerabilityAnalyzed
CVE-2026-35042
fast-jwt provides fast JSON Web Token (JWT) implementation.
HIGH 7.5EPSS 0.15%
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.15%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
Description
fast-jwt provides fast JSON Web Token (JWT) implementation. In 6.1.0 and earlier, fast-jwt does not validate the crit (Critical) Header Parameter defined in RFC 7515 §4.1.11. When a JWS token contains a crit array listing extensions that fast-jwt does not understand, the library accepts the token instead of rejecting it. This violates the MUST requirement in the RFC.
- CVSS 3.1
- 7.5 HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
- EPSS
- 0.15% probability · 5th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-345, CWE-636
- Affected
- nearform/fast-jwt
- Source
- security-advisories@github.com
References
- https://github.com/nearform/fast-jwt/security/advisories/GHSA-hm7r-c7qw-ghp6Exploit, Mitigation, Vendor Advisory
- https://www.rfc-editor.org/rfc/rfc7515.html#section-4.1.11Technical Description
- https://github.com/nearform/fast-jwt/security/advisories/GHSA-hm7r-c7qw-ghp6Exploit, Mitigation, Vendor Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.