Authlib up to 1.9.0 Client Authentication client_id privileges management

Summaryinfo

A vulnerability identified as critical has been detected in Authlib up to 1.9.0. This affects the function ClientConfigurationEndpoint.authenticate_client/ClientConfigurationEndpoint.check_permission of the component Client Authentication. The manipulation of the argument client_id leads to privileges management. This vulnerability is uniquely identified as CVE-2026-116672. The attack is possible to be carried out remotely. No exploit exists. You should upgrade the affected component.

Detailsinfo

A vulnerability, which was classified as critical, has been found in Authlib up to 1.9.0. This issue affects the function ClientConfigurationEndpoint.authenticate_client/ClientConfigurationEndpoint.check_permission of the component Client Authentication. The manipulation of the argument client_id with an unknown input leads to a privileges management vulnerability. Using CWE to declare the problem leads to CWE-269. The product does not properly assign, modify, track, or check privileges for an actor, creating an unintended sphere of control for that actor. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

Authlib is a Python library which builds OAuth and OpenID Connect servers. From 0.15 until 1.9.1, the documented ClientConfigurationEndpoint.authenticate_client and ClientConfigurationEndpoint.check_permission reference implementations look up a target client from request-controlled client_id data and check only whether that target is editable, without verifying that request.credential belongs to the target client. Deployments following both examples can allow a client holding any valid registration access token to read, modify, or delete another client's registration. Changing redirect_uris can enable authorization code or token interception, while deleting registrations can deny service to affected clients. This issue is fixed in version 1.9.1.

The advisory is shared at github.com. The identification of this vulnerability is CVE-2026-116672 since 10/26/2026. The exploitation is known to be easy. The attack may be initiated remotely. Technical details are known, but no exploit is available. MITRE ATT&CK project uses the attack technique T1068 for this issue.

Upgrading to version 1.9.1 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
• 1.9.0

Website

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

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Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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