A vulnerability has been identified in the SIMATIC S7-1500 CPU family and related products that could allow an attacker to cause a denial of service condition. In order to exploit the vulnerability, an attacker must have access to the affected devices on port 102/tcp.
Siemens has released updates for several affected products and recommends to update to the latest versions. Siemens is preparing further updates and recommends specific countermeasures for products where updates are not, or not yet available.

https://cert-portal.siemens.com/productcert/html/ssa-592380.html