Authlib RFC 7592 examples omit registration-access-token client binding

Summary

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.

Remediation

1. Inventory every authlib authlib deployment, including staging.
2. Upgrade authlib authlib to 1.9.1.
3. Confirm the running version after the upgrade.

References

• Advisoryhttps://github.com/advisories/GHSA-c73q-w75p-j82v
• Referencehttps://github.com/authlib/authlib/commit/1bd2a313492ce0a4d0571c150730907aa3fc91ff
• Referencehttps://github.com/authlib/authlib/releases/tag/v1.9.1
• Referencehttps://github.com/authlib/authlib/security/advisories/GHSA-c73q-w75p-j82v
• Referencehttps://nvd.nist.gov/vuln/detail/CVE-2026-116672