{"cve":"CVE-2026-35042","nvd":{"published":"2026-04-06T17:17:13.410","modified":"2026-10-24T13:10:00.147","status":"Analyzed","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_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N","score":7.5},"cwes":["CWE-345","CWE-636"],"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"],"products":["nearform:fast-jwt"],"source":"nvd","synced_at":"2026-10-24T16:53:27.712498749+00:00"},"epss":{"cve":"CVE-2026-35042","score":0.00155,"percentile":0.04606,"date":"2026-10-25"},"kev":null,"osv":[{"id":"GHSA-hm7r-c7qw-ghp6","url":"https://osv.dev/vulnerability/GHSA-hm7r-c7qw-ghp6","summary":"fast-jwt accepts unknown `crit` header extensions (RFC 7515 violation)","modified":"2026-04-06T23:49:39.770398Z","packages":[{"ecosystem":"npm","name":"fast-jwt","purl":"pkg:npm/fast-jwt","ranges":["<=6.1.0"],"fixed":[]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}