Vulnerability Discussion

If an account has an empty password, anyone could log on and run commands with the privileges of that account. Accounts with empty passwords should never be used in operational environments.

Check

To verify that null passwords cannot be used, run the following command:

$ sudo grep -i permitemptypasswords /etc/ssh/sshd_config

PermitEmptyPasswords no

If "PermitEmptyPasswords" is set to "yes", this is a finding.

Fix

Edit the following line in "etc/ssh/sshd_config" to prevent logons with empty passwords.

PermitEmptyPasswords no

The SSH daemon must be restarted for the changes to take effect. To restart the SSH daemon, run the following command:

$ sudo systemctl restart sshd.service