A flaw was found in golang. A panic can be triggered by an attacker in a privileged network position without access to the server certificate's private key, as long as a trusted ECDSA or Ed25519 certificate for the server exists (or can be issued), or the client is configured with Config.InsecureSkipVerify. Clients that disable all TLS_RSA cipher suites (that is, TLS 1.0–1.2 cipher suites without ECDHE), as well as TLS 1.3-only clients, are unaffected.