The Photon operating system must configure sshd to disable X11 forwarding.

X11 is an older, insecure graphics forwarding protocol. It is not used by Photon and should be disabled as a general best practice to limit attack surface area and communication channels.

At the command line, run the following command:

# sshd -T|&grep -i X11Forwarding

Expected result:

X11Forwarding no

If the output does not match the expected result, this is a finding.

Navigate to and open:

/etc/ssh/sshd_config

Ensure the "X11Forwarding" line is uncommented and set to the following:

X11Forwarding no

At the command line, run the following command:

# systemctl restart sshd.service