P-Net before 1.0.4 aborts the Application Relationship of an RPC session when a fragment of a response has been resent without being acknowledged, without checking that the session has an Application Relationship. A request for an existing Application Relationship that is sent on another activity than its Connect, and gets a fragmented response, is handled on a session without one. If the response is not acknowledged, a NULL pointer is dereferenced and the device crashes. A conformant IO-controller does not send such requests. The attacker must have observed the AR UUID of an established Application Relationship and requires ADJACENT network access.