CVE-2026-35042

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

7.5CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

EPSS

0.2% chance of exploitation in the next 30 days; higher than 4% of CVEs (scores of 2026-10-25)

CWEs

CWE-345, CWE-636

Published

2026-04-06

Modified

2026-10-24

Record from

the NVD, synced 2026-10-24

Affected

• nearform:fast-jwt

Packages (OSV)

References

• https://github.com/nearform/fast-jwt/security/advisories/GHSA-hm7r-c7qw-ghp6
• https://www.rfc-editor.org/rfc/rfc7515.html#section-4.1.11
• https://github.com/nearform/fast-jwt/security/advisories/GHSA-hm7r-c7qw-ghp6

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