An attacker can send special message that will cause an application to crash. This is usually the result of a known problem in a stack or application. These system bugs can allow a Clientto issue a command that would cause the Serverto crash, as an alternate it might be a Serverthat can respond to a legitimate message with a response that would cause the Clientto crash. The attacker could also be a Publisherthat issues a Messagethat would cause Subscribersto crash.