The SSH daemon must be configured to not allow X11 forwarding.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-39265	GEN005519-ESXI5-000102	SV-51081r1_rule		Medium

Description
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 and should not be enabled unless needed.

STIG	Date
VMware ESXi Server 5.0 Security Technical Implementation Guide	2017-01-06

Details

Check Text ( C-46529r1_chk )
Disable lock down mode. Enable the ESXi Shell. Check the SSH daemon configuration for the X11 forwarding setting. # grep -i "^X11Forwarding" /etc/ssh/sshd_config If "X11Forwarding" is set to "yes", this is a finding. Re-enable lock down mode.

Fix Text (F-44244r1_fix)
Disable lock down mode. Enable the ESXi Shell. Edit the SSH daemon configuration and add/modify the "X11Forwarding" configuration, setting it to "no". # vi /etc/ssh/sshd_config Re-enable lock down mode.