{"id":"UBUNTU-CVE-2026-48523","details":"PyJWT is a JSON Web Token implementation in Python. From 2.9.0 to 2.12.1, there is a verifier-side algorithm allow-list bypass when jwt.decode() or jwt.decode_complete() are called with a PyJWK key. The token header alg is checked against the caller-supplied algorithms allow-list, but signature verification is performed with the algorithm bound to the PyJWK object instead of the header algorithm. An attacker who controls a registered JWK/JWKS private key can sign with a disallowed algorithm, advertise an allowed algorithm in the JWT header, and still be accepted. The issue affects the documented PyJWKClient.get_signing_key_from_jwt(...) flow. This vulnerability is fixed in 2.13.0.","modified":"2026-09-28T11:30:25.343451960Z","published":"2026-05-28T16:16:00Z","related":["USN-8823-1"],"upstream":["CVE-2026-48523"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2026-48523"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2026-48523"},{"type":"REPORT","url":"https://github.com/jpadilla/pyjwt/security/advisories/GHSA-jq35-7prp-9v3f"},{"type":"REPORT","url":"https://github.com/jpadilla/pyjwt/commit/95791b1759b8aa4f2203575d344d5c78564cdc81"},{"type":"ADVISORY","url":"https://ubuntu.com/security/notices/USN-8823-1"}],"affected":[{"package":{"name":"pyjwt","ecosystem":"Ubuntu:25.10","purl":"pkg:deb/ubuntu/pyjwt?arch=source&distro=questing"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.10.1-2","2.10.1-2ubuntu0.1"],"ecosystem_specific":{"binaries":[{"binary_name":"python3-jwt","binary_version":"2.10.1-2ubuntu0.1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-48523.json"}},{"package":{"name":"pyjwt","ecosystem":"Ubuntu:26.04:LTS","purl":"pkg:deb/ubuntu/pyjwt?arch=source&distro=resolute"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.10.1-4ubuntu1.1"}]}],"versions":["2.10.1-2","2.10.1-3","2.10.1-3build1","2.10.1-4","2.10.1-4ubuntu1"],"ecosystem_specific":{"binaries":[{"binary_name":"python3-jwt","binary_version":"2.10.1-4ubuntu1.1"}],"availability":"No subscription required"},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-48523.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N"},{"type":"Ubuntu","score":"medium"}]}