Authlib up to 1.8.x JWT Bearer Grant JWTBearerGrant.get_audiences improper authorization

Summaryinfo

A vulnerability was found in Authlib up to 1.8.x. It has been rated as critical. The impacted element is the function JWTBearerGrant.get_audiences of the component JWT Bearer Grant. This manipulation causes improper authorization. The identification of this vulnerability is CVE-2026-114618. It is possible to initiate the attack remotely. There is no exploit available. Upgrading the affected component is advised.

Detailsinfo

A vulnerability was found in Authlib up to 1.8.x. It has been declared as critical. Affected by this vulnerability is the function JWTBearerGrant.get_audiences of the component JWT Bearer Grant. The manipulation with an unknown input leads to a improper authorization vulnerability. The CWE definition for the vulnerability is CWE-285. The product does not perform or incorrectly performs an authorization check when an actor attempts to access a resource or perform an action. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

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.

The advisory is shared at github.com. This vulnerability is known as CVE-2026-114618 since 10/21/2026. The exploitation appears to be easy. The attack can be launched remotely. Technical details are known, but no exploit is available. MITRE ATT&CK project uses the attack technique T1548.002 for this issue.

Upgrading to version 1.9.0 eliminates this vulnerability.

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Productinfo

Name

• Authlib

Version

• 1.0
• 1.1
• 1.2
• 1.3
• 1.4
• 1.5
• 1.6
• 1.7
• 1.8

Website

• Product: https://github.com/authlib/authlib/

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