Title

The SSH client must be configured to not allow X11 forwarding. (Cat III impact)

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. If this function is necessary to support a valid mission requirement, its use must be authorized and approved in the system accreditation package.

Check Content

Check the SSH client configuration for the X11 forwarding setting. # grep -i ForwardX11 /etc/ssh/ssh_config | grep -v '^#' If no lines are returned, or the returned setting has a value evaluating to yes, this is a finding.

Fix Text

Edit the SSH client configuration and change or add the ForwardX11 setting to no.

Additional Identifiers

Rule ID: SV-26762r1_rule

Vulnerability ID: V-22469

Group Title: GEN005520

Expert Comments

CCIs tied to check.

Controls tied to check. These are derived from the CCIs shown above.