A vulnerability has been identified in SIMATIC ET 200SP Open Controller (All versions >= V2.0 and < V2.1.6), SIMATIC S7-1500 Software Controller (All versions >= V2.0 and < V2.5), SIMATIC S7-1500 incl. F (All versions >= V2.0 and < V2.5). An attacker can cause a denial-of-service condition on the network stack by sending a large number of specially crafted packets to the PLC. The PLC will lose its ability to communicate over the network. This vulnerability could be exploited by an attacker with network access to the affected systems. Successful exploitation requires no privileges and no user interaction. An attacker could use this vulnerability to compromise availability of the network connectivity. At the time of advisory publication no public exploitation of this vulnerability was known.