This vulnerability allows remote attackers to create a denial-of-service condition on affected installations of Unified Automation OPC UA C++ Demo Server 1.7.6-537. Authentication is not required to exploit this vulnerability. The specific flaw exists within the OpcUa_SecureListener_ProcessSessionCallRequest method. A crafted OPC UA message can force the server to incorrectly update a reference count. An attacker can leverage this vulnerability to create a denial-of-service condition on the system. Was ZDI-CAN-16927.