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

From VMware ESXi Server 5.0 Security Technical Implementation Guide

Associated with: CCI-000366

SV-51081r1_rule The SSH daemon must be configured to not allow X11 forwarding.

Vulnerability discussion

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.

Check content

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

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.

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