The rmcp OAuth client versions from 2.0.0 up to but not including 3.7.0 have a server-side request forgery (SSRF) vulnerability. The client only inspected host strings to decide if it should fetch authorization server metadata, failing to resolve hostnames to their IP addresses. This allowed malicious servers to cause the client to send requests to internal IP addresses, potentially reaching unauthenticated internal HTTP services. The issue was fixed in version 3.7.0 by adding DNS resolution and address policy checks on all resolved addresses and redirects.