Zyxel CloudCNM SecuManager 3.1.0 and 3.1.1 has a hardcoded DSA SSH key for the root account within the /opt/axess chroot directory tree.
https://www.zyxel.com/support/vulnerabilities-of-CloudCNM-SecuManager.shtml
https://pierrekim.github.io/blog/2020-03-09-zyxel-secumanager-0day-vulnerabilities.html