STIGQter: STIG Summary: Canonical Ubuntu 24.04 LTS Security Technical Implementation Guide Version: 1 Release: 6 Benchmark Date: 01 Jul 2026:

Ubuntu 24.04 LTS SSH daemon must prevent remote hosts from connecting to the proxy display.

DISA Rule

SV-270709r1208698_rule

Vulnerability Number

V-270709

Group Title

SRG-OS-000480-GPOS-00227

Rule Version

UBTU-24-300023

Severity

CAT II

CCI(s)

• CCI-000366 - Implement the security configuration settings.

Weight

10

Fix Recommendation

Configure the SSH daemon to prevent remote hosts from connecting to the proxy display.

Edit the "/etc/ssh/sshd_config" file to uncomment or add the line for the "X11UseLocalhost" keyword and set its value to "yes" (this file may be named differently or be in a different location if using a version of SSH that is provided by a third-party vendor):

X11UseLocalhost yes

Restart SSH for the changes to take effect:

$ sudo systemctl restart ssh

Check Contents

Verify the SSH daemon prevents remote hosts from connecting to the proxy display with the following command:

$ sudo grep -ir x11uselocalhost /etc/ssh/sshd_config*
X11UseLocalhost yes

If the "X11UseLocalhost" keyword is set to "no", is commented out, is missing, or multiple conflicting results are returned, this is a finding.

Vulnerability Number

V-270709

Documentable

False

Rule Version

UBTU-24-300023

Severity Override Guidance

Verify the SSH daemon prevents remote hosts from connecting to the proxy display with the following command:

$ sudo grep -ir x11uselocalhost /etc/ssh/sshd_config*
X11UseLocalhost yes

If the "X11UseLocalhost" keyword is set to "no", is commented out, is missing, or multiple conflicting results are returned, this is a finding.

Check Content Reference

M

Target Key

5673