{"id":"CVE-2026-27962","summary":"Authlib JWS JWK Header Injection: Signature Verification Bypass","details":"Authlib is a Python library which builds OAuth and OpenID Connect servers. Prior to version 1.6.9, a JWK Header Injection vulnerability in authlib's JWS implementation allows an unauthenticated attacker to forge arbitrary JWT tokens that pass signature verification. When key=None is passed to any JWS deserialization function, the library extracts and uses the cryptographic key embedded in the attacker-controlled JWT jwk header field. An attacker can sign a token with their own private key, embed the matching public key in the header, and have the server accept the forged token as cryptographically valid — bypassing authentication and authorization entirely. This issue has been patched in version 1.6.9.","aliases":["GHSA-wvwj-cvrp-7pv5"],"modified":"2026-04-10T05:37:34.285816Z","published":"2026-03-16T17:34:38.946Z","related":["SUSE-SU-2026:0975-1","openSUSE-SU-2026:20392-1"],"database_specific":{"cwe_ids":["CWE-347"],"cna_assigner":"GitHub_M","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/27xxx/CVE-2026-27962.json"},"references":[{"type":"WEB","url":"https://github.com/authlib/authlib/releases/tag/v1.6.9"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/27xxx/CVE-2026-27962.json"},{"type":"ADVISORY","url":"https://github.com/authlib/authlib/security/advisories/GHSA-wvwj-cvrp-7pv5"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-27962"},{"type":"FIX","url":"https://github.com/authlib/authlib/commit/a5d4b2d4c9e46bfa11c82f85fdc2bcc0b50ae681"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/authlib/authlib","events":[{"introduced":"0"},{"fixed":"9266eaa2227ad7e21dc731b2a4a01909aabd934b"}]}],"versions":["v0.1","v0.10","v0.11","v0.12","v0.13","v0.14","v0.14.1","v0.14.2","v0.14.3","v0.15","v0.2","v0.2.1","v0.3","v0.4","v0.4.1","v0.5","v0.5.1","v0.6","v0.7","v0.8","v0.9","v1.0.0","v1.0.1","v1.1.0","v1.2.0","v1.2.1","v1.3.0","v1.3.2","v1.4.0","v1.4.1","v1.5.0","v1.5.1","v1.5.2","v1.6.0","v1.6.1","v1.6.2","v1.6.3","v1.6.4","v1.6.5","v1.6.6","v1.6.7","v1.6.8"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-27962.json"}},{"ranges":[{"type":"GIT","repo":"https://github.com/lepture/authlib","events":[{"introduced":"0"},{"fixed":"9266eaa2227ad7e21dc731b2a4a01909aabd934b"}],"database_specific":{"versions":[{"introduced":"0"},{"fixed":"1.6.9"}]}}],"versions":["v0.1","v0.10","v0.11","v0.12","v0.13","v0.14","v0.14.1","v0.14.2","v0.14.3","v0.15","v0.2","v0.2.1","v0.3","v0.4","v0.4.1","v0.5","v0.5.1","v0.6","v0.7","v0.8","v0.9","v1.0.0","v1.0.1","v1.1.0","v1.2.0","v1.2.1","v1.3.0","v1.3.2","v1.4.0","v1.4.1","v1.5.0","v1.5.1","v1.5.2","v1.6.0","v1.6.1","v1.6.2","v1.6.3","v1.6.4","v1.6.5","v1.6.6","v1.6.7","v1.6.8"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-27962.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N"}]}