{"id":"UBUNTU-CVE-2026-27962","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.","modified":"2026-07-17T01:21:29.838318199Z","published":"2026-03-16T18:16:00Z","related":["USN-8557-1"],"upstream":["CVE-2026-27962"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2026-27962"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2026-27962"},{"type":"REPORT","url":"https://github.com/authlib/authlib/security/advisories/GHSA-wvwj-cvrp-7pv5"},{"type":"ADVISORY","url":"https://ubuntu.com/security/notices/USN-8557-1"}],"affected":[{"package":{"name":"python-authlib","ecosystem":"Ubuntu:Pro:22.04:LTS","purl":"pkg:deb/ubuntu/python-authlib?arch=source&distro=esm-apps%2Fjammy"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.15.5-1ubuntu0.1~esm2"}]}],"versions":["0.15.4-1","0.15.5-1","0.15.5-1ubuntu0.1~esm1"],"ecosystem_specific":{"binaries":[{"binary_name":"python3-authlib","binary_version":"0.15.5-1ubuntu0.1~esm2"}],"availability":"Available with Ubuntu Pro: https://ubuntu.com/pro"},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-27962.json"}},{"package":{"name":"python-authlib","ecosystem":"Ubuntu:Pro:24.04:LTS","purl":"pkg:deb/ubuntu/python-authlib?arch=source&distro=esm-apps%2Fnoble"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.3.0-1ubuntu0.1~esm2"}]}],"versions":["1.2.1-1","1.3.0-1","1.3.0-1ubuntu0.1~esm1"],"ecosystem_specific":{"binaries":[{"binary_version":"1.3.0-1ubuntu0.1~esm2","binary_name":"python3-authlib"}],"availability":"Available with Ubuntu Pro: https://ubuntu.com/pro"},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-27962.json"}},{"package":{"name":"python-authlib","ecosystem":"Ubuntu:25.10","purl":"pkg:deb/ubuntu/python-authlib?arch=source&distro=questing"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.5.1-1","1.5.2-1","1.6.0-1"],"ecosystem_specific":{"binaries":[{"binary_version":"1.6.0-1","binary_name":"python3-authlib"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-27962.json"}},{"package":{"name":"python-authlib","ecosystem":"Ubuntu:Pro:26.04:LTS","purl":"pkg:deb/ubuntu/python-authlib?arch=source&distro=esm-apps%2Fresolute"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.6.7-1ubuntu0.1~esm1"}]}],"versions":["1.6.0-1","1.6.5-1","1.6.6-1","1.6.7-1"],"ecosystem_specific":{"binaries":[{"binary_version":"1.6.7-1ubuntu0.1~esm1","binary_name":"python3-authlib"}],"availability":"Available with Ubuntu Pro: https://ubuntu.com/pro"},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-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"},{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N"},{"type":"Ubuntu","score":"medium"}]}