A vulnerability has been identified in SIMATIC S7-1200 (All versions), SIMATIC S7-1500 (All Versions < V2.6). An attacker could exhaust the available connection pool of an affected device by opening a sufficient number of connections to the device. Successful exploitation requires an attacker to be able to send packets to port 102/tcp of the affected device. No user interaction and no user privileges are required to exploit the vulnerability. The vulnerability, if exploited, could cause a Denial-of-Service condition impacting the availability of the system. At the time of advisory publication no public exploitation of this vulnerability was known.
https://cert-portal.siemens.com/productcert/pdf/ssa-584286.pdf