A flaw was identified in Keycloak’s OpenID Connect Dynamic Client Registration feature when clients authenticate using private_key_jwt. The issue allows a client to specify an arbitrary jwks_uri, which Keycloak then retrieves without validating the destination. This enables attackers to coerce the Keycloak server into making HTTP requests to internal or restricted network resources. As a result, attackers can probe internal services and cloud metadata endpoints, creating an information disclosure and reconnaissance risk.
Weakness
The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination.