Information
The PermitEmptyPasswords parameter specifies if the SSH server allows login to accounts with empty password strings.
More information about the openSSH server configuration is available in the "Configure SSH Server" section overview.
Disallowing remote shell access to accounts that have an empty password reduces the probability of unauthorized access to the system.
Solution
Create or edit a *.conf file in the /etc/ssh/sshd_config.d/ directory to set the PermitEmptyPasswords parameter to no above any Include and Match entries as follows:
PermitEmptyPasswords no