{"id":"CVE-2026-75509","summary":"joserfc claim-validation bypass via array-typed single-string claims (iss/sub/jti)","details":"joserfc is a Python library that provides an implementation of several JSON Object Signing and Encryption (JOSE) standards. Prior to version 1.7.3, JWTClaimsRegistry applies membership matching to list-valued iss and sub claims, allowing an array-valued iss that contains the expected issuer to pass an intended equality check and enabling issuer-validation bypass. This issue is fixed in version 1.7.3.","aliases":["GHSA-r74j-q665-7rpj"],"modified":"2026-08-27T11:47:35.685018984Z","published":"2026-08-24T20:08:07.088Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/75xxx/CVE-2026-75509.json","cna_assigner":"GitHub_M","cwe_ids":["CWE-290","CWE-345"]},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/75xxx/CVE-2026-75509.json"},{"type":"ADVISORY","url":"https://github.com/authlib/joserfc/security/advisories/GHSA-r74j-q665-7rpj"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-75509"},{"type":"FIX","url":"https://github.com/authlib/joserfc/commit/76ee6a59bf5773c0af00b99076c5e199031f97f1"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/authlib/joserfc","events":[{"introduced":"0"},{"fixed":"76ee6a59bf5773c0af00b99076c5e199031f97f1"}],"database_specific":{"extracted_events":[{"introduced":"0"},{"fixed":"1.7.3"}],"source":["AFFECTED_FIELD","REFERENCES"]}}],"versions":["1.7.2","1.7.1","1.7.0","1.6.7","1.6.5","1.6.4","1.6.3","1.6.2","1.6.1","1.6.0","1.5.0","1.4.3","1.4.1","1.4.0","1.3.3","1.3.2","1.3.1","1.3.0","1.2.2","1.2.1","1.2.0","1.1.0","1.0.4","1.0.3","1.0.2","1.0.1","1.0.0","0.12.0","0.11.1","0.11.0","0.10.0","0.9.0","0.8.0","0.7.0","0.6.0","0.5.0","0.4.0","0.3.0","0.2.0"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-75509.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:N"}]}