CVE-2026-114618

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

Published Oct 22, 2026 CVSS 3.1 · 6.8 Medium EPSS < 1% KEV · Not listed
Description
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Github GHSA Github GHSA GHSA-fch4-3c6x-j4gc Authlib: Default JWT bearer grant accepts assertions for the wrong audience
History
Type Values Removed Values Added
CPEs cpe:2.3:a:authlib:authlib:*:*:*:*:*:*:*:*
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'poc', 'Technical Impact': 'total'}, 'version': '2.0.3'}

Type Values Removed Values Added
First Time appeared Authlib
Authlib authlib
Vendors & Products Authlib
Authlib authlib
Type Values Removed Values Added
Description 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.
Title Authlib: Default JWT bearer grant accepts assertions for the wrong audience
Weaknesses CWE-1188
CWE-287
References
Metrics cvssV3_1

{'score': 6.8, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
Oct 29, 2026, 12:29 PM
Reserved
Oct 21, 2026, 8:34 PM
Status
Analyzed
Published
Oct 22, 2026, 10:18 PM
Modified
Oct 29, 2026, 2:53 PM
Severity
Moderate
Public date
Oct 22, 2026, 9:28 PM