SENTRON 3KC ATC6 Expansion Module Ethernet exposes an unused, unstable http service at port 80/tcp on the Modbus-TCP Ethernet, which could allow an attacker on the same Modbus network to create a denial of service condition that forces the device to reboot.
Siemens is preparing fix versions and recommends specific countermeasures for products where fixes are not, or not yet available.

https://cert-portal.siemens.com/productcert/html/ssa-918992.html