Vulnerability Discussion

SSH trust relationships mean a compromise on one host can allow an attacker to move trivially to other hosts.

Check

Verify the SSH daemon does not allow rhosts authentication with the following command:

$ sudo /usr/sbin/sshd -dd 2>&1 | awk '/filename/ {print $4}' | tr -d '\r' | tr '\n' ' ' | xargs sudo grep -iH '^\s*ignorerhosts'

IgnoreRhosts yes

If the value is returned as "no", the returned line is commented out, or no output is returned, this is a finding.

Fix

Configure the SSH daemon to not allow rhosts authentication.

Add the following line in "/etc/ssh/sshd_config", or uncomment the line and set the value to "yes":

IgnoreRhosts yes

The SSH service must be restarted for changes to take effect:

$ sudo systemctl restart sshd.service