Authlib: Default JWT bearer grant accepts assertions for the wrong audience

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-114618
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-22 22:18:04 UTC
Updated2026-10-22 22:18:04 UTC
DescriptionAuthlib 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.

Risk And Classification

Primary CVSS: v3.1 6.8 MEDIUM from [email protected]

CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N

Problem Types: CWE-287 | CWE-1188 | CWE-287 CWE-287: Improper Authentication | CWE-1188 CWE-1188: Insecure Default Initialization of Resource

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary6.8MEDIUMCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N
3.1CNADECLARED6.8MEDIUMCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
High
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Authlib Authlib affected < 1.9.0 Not specified

References

ReferenceSourceLinkTags
github.com/authlib/authlib/security/advisories/GHSA-fch4-3c6x-j4gc [email protected] github.com
github.com/authlib/authlib/pull/945 [email protected] github.com
github.com/authlib/authlib/commit/e3bd41cb29dcfee434453b135ffb487884baeedf [email protected] github.com
github.com/authlib/authlib/releases/tag/v1.9.0 [email protected] github.com
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