STIGQter: STIG Summary: Red Hat Enterprise Linux 9 Security Technical Implementation Guide Version: 2 Release: 9 Benchmark Date: 01 Jul 2026:

RHEL 9 SSH daemon must prevent remote hosts from connecting to the proxy display.

DISA Rule

SV-258011r1045079_rule

Vulnerability Number

V-258011

Group Title

SRG-OS-000480-GPOS-00227

Rule Version

RHEL-09-255175

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.

Add the following line to "/etc/ssh/sshd_config" or to a file in "/etc/ssh/sshd_config.d", or uncomment the line and set the value to "yes":

X11UseLocalhost yes

The SSH service must be restarted for changes to take effect:

$ sudo systemctl restart sshd.service

Check Contents

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

$ sudo /usr/sbin/sshd -dd 2>&1 | awk '/filename/ {print $4}' | tr -d '\r' | tr '\n' ' ' | xargs sudo grep -iH '^\s*x11uselocalhost'

X11UseLocalhost yes

If the "X11UseLocalhost" keyword is set to "no", is missing, or is commented out, this is a finding.

Vulnerability Number

V-258011

Documentable

False

Rule Version

RHEL-09-255175

Severity Override Guidance

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

$ sudo /usr/sbin/sshd -dd 2>&1 | awk '/filename/ {print $4}' | tr -d '\r' | tr '\n' ' ' | xargs sudo grep -iH '^\s*x11uselocalhost'

X11UseLocalhost yes

If the "X11UseLocalhost" keyword is set to "no", is missing, or is commented out, this is a finding.

Check Content Reference

M

Target Key

5551