P-Net before 1.0.3 does not release the RPC session allocated for an RPC request that names an unknown interface or object UUID, and does not start a timeout for it. Repeated requests with different activity UUIDs exhaust the available sessions. Once they are exhausted the device no longer answers new RPC requests, including Endpoint Mapper Lookup and Connect, until it is restarted. A remote unauthenticated attacker can use this to cause a denial of service.