A vulnerability has been identified in SIMATIC CN 4100 (All versions < V3.0). The affected device contains hard coded password which is used for the privileged system user `root` and for the boot loader `GRUB` by default . An attacker who manages to crack the password hash gains root access to the device.
https://www.cisa.gov/news-events/ics-advisories/icsa-24-137-06
https://cert-portal.siemens.com/productcert/html/ssa-273900.html