Vulnerability Discussion

SSH daemon privilege separation causes the SSH process to drop root privileges when not needed, which would decrease the impact of software vulnerabilities in the nonprivileged section.

Check

Verify the SSH daemon performs privilege separation 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*useprivilegeseparation'

UsePrivilegeSeparation sandbox

If the "UsePrivilegeSeparation" keyword is set to "no", the returned line is commented out, or no output is returned, this is a finding.

Fix

Configure the SSH daemon to perform privilege separation.

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

UsePrivilegeSeparation sandbox

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

$ sudo systemctl restart sshd.service