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    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.

    Published:Apr 6, 2026
    Last Modified:Apr 13, 2026
    EPS:Apr 6, 2026
    EPSS Score:0.0002
    CVSS Score:7.5

    Affected Products

    Vendor
    Nearform
    Product
    Fast-jwt

    Exploits

    https://github.com/nearform/fast-jwt/security/advisories/GHSA-hm7r-c7qw-ghp6https://github.com/nearform/fast-jwt/security/advisories/GHSA-hm7r-c7qw-ghp6

    Related CVEs

    CVE-2026-44351 (CVSS 9.1) — fast-jwt provides fast JSON Web Token (JWT) implementation. Prior to 6.2.4, a critical authentication-bypass v…
    CVE-2026-35041 (CVSS 4.2) — fast-jwt provides fast JSON Web Token (JWT) implementation. From 5.0.0 to 6.2.0, a denial-of-service condition…
    CVE-2026-35040 (CVSS 5.3) — fast-jwt provides fast JSON Web Token (JWT) implementation. Prior to 6.2.1, using certain modifiers on RegExp …
    CVE-2026-35039 (CVSS 9.1) — fast-jwt provides fast JSON Web Token (JWT) implementation. From 0.0.1 to before 6.2.0, setting up a custom ca…
    CVE-2026-34950 (CVSS 9.1) — fast-jwt provides fast JSON Web Token (JWT) implementation. In 6.1.0 and earlier, the publicKeyPemMatcher rege…
    CVE-2025-30144 (CVSS 6.5) — fast-jwt provides fast JSON Web Token (JWT) implementation. Prior to 5.0.6, the fast-jwt library does not prop…
    CVE-2023-48223 (CVSS 5.9) — fast-jwt provides fast JSON Web Token (JWT) implementation. Prior to version 3.3.2, the fast-jwt library does …

    Common Vulnerability Scoring System

    Attack Vector
    Network
    Adjacent
    Local
    Physical
    Privileges Required
    None
    Low
    High
    User Interaction
    None
    Required
    Scope
    Unchanged
    Changed
    Confidentiality
    None
    Low
    High
    Integrity
    None
    Low
    High
    Availability
    None
    Low
    High