Sunshine is a self-hosted game stream host for Moonlight. Clients that experience a MITM attack during the pairing process may inadvertantly allow access to an unintended client rather than failing authentication due to a PIN validation error. The pairing attempt fails due to the incorrect PIN, but the certificate from the forged pairing attempt is incorrectly persisted prior to the completion of the pairing request. This allows access to the certificate belonging to the attacker.
The product does not adequately verify the identity of actors at both ends of a communication channel, or does not adequately ensure the integrity of the channel, in a way that allows the channel to be accessed or influenced by an actor that is not an endpoint.