Affected SIPROTEC 5 devices do not properly limit the bandwidth for incoming network packets over their local USB port. This could allow an attacker with physical access to send specially crafted packets with high bandwidth to the affected devices thus forcing them to exhaust their memory and stop responding to any network traffic via the local USB port. Affected devices reset themselves automatically after a successful attack and the protection function is not affected of this vulnerability. Siemens has released new versions for the affected products and recommends to update to the latest versions.
https://cert-portal.siemens.com/productcert/html/ssa-894058.html