{"id":"PYSEC-2026-4358","details":"Authlib is a Python library which builds OAuth and OpenID Connect servers. Prior to 1.9.0, the default RFC 7523 JWTBearerGrant.get_audiences() returns an empty list, causing JWTBearerGrant.verify_claims() to require only that an aud claim exists without matching the current authorization server. An attacker holding a legitimate assertion for another service can present it to a server that shares the signing key and uses the default grant, obtaining an access token across a trust boundary. Implementations that override get_audiences() with the server's valid audience identifiers are not affected. This issue is fixed in version 1.9.0.","aliases":["CVE-2026-114618","GHSA-fch4-3c6x-j4gc"],"modified":"2026-10-30T10:00:02.209169691Z","published":"2026-10-22T22:18:04.747Z","references":[{"type":"ADVISORY","url":"https://github.com/authlib/authlib/releases/tag/v1.9.0"},{"type":"FIX","url":"https://github.com/authlib/authlib/commit/e3bd41cb29dcfee434453b135ffb487884baeedf"},{"type":"FIX","url":"https://github.com/authlib/authlib/pull/945"},{"type":"EVIDENCE","url":"https://github.com/authlib/authlib/security/advisories/GHSA-fch4-3c6x-j4gc"}],"affected":[{"package":{"name":"authlib","ecosystem":"PyPI","purl":"pkg:pypi/authlib"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.9.0"}]}],"versions":["0.1","0.10","0.11","0.12","0.12.1","0.13","0.14","0.14.1","0.14.2","0.14.3","0.15","0.15.1","0.15.2","0.15.3","0.15.4","0.15.5","0.15.6","0.1rc0","0.2","0.2.1","0.3","0.4","0.4.1","0.5","0.5.1","0.6","0.7","0.8","0.9","1.0.0","1.0.0a1","1.0.0a2","1.0.0b1","1.0.0b2","1.0.0rc1","1.0.1","1.1.0","1.2.0","1.2.1","1.3.0","1.3.1","1.3.2","1.4.0","1.4.1","1.5.0","1.5.1","1.5.2","1.6.0","1.6.1","1.6.10","1.6.11","1.6.12","1.6.2","1.6.3","1.6.4","1.6.5","1.6.6","1.6.7","1.6.8","1.6.9","1.7.0","1.7.1","1.7.2","1.8.0"],"ecosystem_specific":{},"database_specific":{"source":"https://github.com/pypa/advisory-database/blob/main/vulns/authlib/PYSEC-2026-4358.yaml"}}],"schema_version":"1.9.2","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N"}]}