{"id":"CVE-2026-35042","state":"PUBLISHED","title":"fast-jwt accepts unknown `crit` header extensions (RFC 7515 §4.1.11 MUST violation)","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.","publishedAt":"2026-04-06T17:02:12.180Z","updatedAt":"2026-04-07T15:59:49.872Z","severity":{"score":7.5,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N","source":"GitHub_M"},"assigner":"GitHub_M","products":["nearform fast-jwt"],"affected":[{"vendor":"nearform","product":"fast-jwt","versions":[{"version":"<= 6.1.0","status":"affected"}]}],"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"],"weaknesses":["CWE-345","CWE-636"],"ingestedAt":"2026-10-29T20:11:40.391Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/35xxx/CVE-2026-35042.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-35042","state":"PUBLISHED","datePublished":"2026-04-06T17:02:12.180Z","dateUpdated":"2026-04-07T15:59:49.872Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2026-03-31T21:06:06.428Z"},"containers":{"cna":{"title":"fast-jwt accepts unknown `crit` header extensions (RFC 7515 §4.1.11 MUST violation)","descriptions":[{"lang":"en","value":"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."}],"affected":[{"vendor":"nearform","product":"fast-jwt","versions":[{"version":"<= 6.1.0","status":"affected"}]}],"references":[{"url":"https://github.com/nearform/fast-jwt/security/advisories/GHSA-hm7r-c7qw-ghp6","name":"https://github.com/nearform/fast-jwt/security/advisories/GHSA-hm7r-c7qw-ghp6","tags":["x_refsource_CONFIRM"]},{"url":"https://www.rfc-editor.org/rfc/rfc7515.html#section-4.1.11","name":"https://www.rfc-editor.org/rfc/rfc7515.html#section-4.1.11","tags":["x_refsource_MISC"]}],"metrics":[{"cvssV3_1":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"NONE","baseScore":7.5,"baseSeverity":"HIGH","confidentialityImpact":"NONE","integrityImpact":"HIGH","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N","version":"3.1"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-345","lang":"en","description":"CWE-345: Insufficient Verification of Data Authenticity","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-636","lang":"en","description":"CWE-636: Not Failing Securely ('Failing Open')","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2026-04-06T17:02:12.180Z"},"source":{"advisory":"GHSA-hm7r-c7qw-ghp6","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","references":[{"url":"https://github.com/nearform/fast-jwt/security/advisories/GHSA-hm7r-c7qw-ghp6","tags":["exploit"]}],"metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-04-07T15:19:36.239438Z","id":"CVE-2026-35042","options":[{"Exploitation":"poc"},{"Automatable":"yes"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-04-07T15:59:49.872Z"}}]}}}