CVE-2026-35042
fast-jwt accepts unknown `crit` header extensions (RFC 7515 §4.1.11 MUST violation)
CVSS Score
7.5
EPSS Score
0.0%
EPSS Percentile
3th
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.
| CWE | CWE-345 CWE-636 |
| Vendor | nearform |
| Product | fast-jwt |
| Published | Apr 6, 2026 |
| Last Updated | Apr 7, 2026 |
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CVSS v3 Breakdown
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
None
Affected Versions
nearform / fast-jwt
<= 6.1.0