Title

The SSH daemon 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 daemon configuration for the X11 forwarding setting. # grep -i X11Forwarding /etc/ssh/sshd_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 daemon configuration and change or add the X11Forwarding setting to no.

Additional Identifiers

Rule ID: SV-26761r1_rule

Vulnerability ID: V-22468

Group Title: GEN005519

Expert Comments

CCIs tied to check.

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