CVE-2026-114618
Authlib: Default JWT bearer grant accepts assertions for the wrong audience
MEDIUM 6.8EPSS 0.4%
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.
- Affected
- authlib
- CVSS v3.1 GITHUB
- 6.8 MEDIUM
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N - EPSS
- 0.35% chance of exploitation in the next 30 days, 29th percentile
- Published
- 2026-10-22
- Updated
- 2026-10-29
Proof-of-concept exploits (1)
CVE references
- authlib/authlib/commit/e3bd41cb29dcfee434453b135ffb487884baeedfPATCH
- authlib/authlib/pull/945PATCH
- authlib/authlib/releases/tag/v1.9.0REFERENCE
- authlib/authlib/security/advisories/GHSA-fch4-3c6x-j4gcVENDOR