The ESXi host Secure Shell (SSH) daemon must be configured to not allow X11 forwarding.

X11 forwarding over SSH allows for the secure remote execution of X11-based applications. This feature can increase the attack surface of an SSH connection.

From an ESXi shell, run the following command:

# /usr/lib/vmware/openssh/bin/sshd -T|grep x11forwarding

Expected result:

x11forwarding no

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

From an ESXi shell, add or correct the following line in "/etc/ssh/sshd_config":

X11Forwarding no