- Severity: HIGH
- CVE: CVE-2026-116672
- Ecosystems: pip
- Packages: Authlib
## Description
### Summary
RFC 7592 (OAuth 2.0 Dynamic Client Registration Management Protocol) lets a previously registered client read, update, or delete its own registration, authenticated by a `registration_access_token` issued specifically to that client at registration time. The entire security model of this protocol depends on the server verifying that the token presented in the request actually belongs to the client identified in the request, not merely that the token is valid for some client.
Authlib’s `ClientConfigurationEndpoint` implements the control flow correctly in structure, calling `authenticate_token`, then `authenticate_client`, then `check_permission`, and treats all three as abstract methods that “Developers MUST implement in subclass.” The problem is that the documented example implementations for these methods, taken together exactly as written, never perform the one check that matters: binding the authenticated token to the specific client being accessed. A developer who implements these methods by following the provided examples ends up with a complete authorization bypass on this endpoint.
### Details
`authenticate_client`’s documented example (`authlib/oauth2/rfc7592/endpoint.py`):
“`python
def authenticate_client(self, request):
“””Read a client from the request payload.
Developers MUST implement this method in subclass::
def authenticate_client(self, request):
client_id = request.payload.data.get(“client_id”)
return Client.get(client…
Source: GitHub Security Advisories · 2026-10-30