CVE-2026-35042
HIGHfast-jwt accepts unknown `crit` header extensions (RFC 7515 §4.1.11 MUST violation)
Title source: cnaDescription
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.
References (2)
Core 2
Core References
X_Refsource_Misc x_refsource_misc
https://www.rfc-editor.org/rfc/rfc7515.html#section-4.1.11
X_Refsource_Confirm x_refsource_confirm
https://github.com/nearform/fast-jwt/security/advisories/GHSA-hm7r-c7qw-ghp6
Scores
CVSS v3
7.5
EPSS
0.0015
EPSS Percentile
5.0%
Attack Vector
NETWORK
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
CISA SSVC
Vulnrichment
Exploitation
poc
Automatable
yes
Technical Impact
partial
Details
CWE
CWE-345
CWE-636
Status
published
Products (3)
nearform/fast-jwt
< 6.2.0
nearform/fast-jwt
<= 6.1.0
npm/fast-jwt
0npm
Published
Apr 06, 2026
Tracked Since
Apr 06, 2026