RHEL 9 SSH daemon must prevent remote hosts from connecting to the proxy display.
An XCCDF Rule
Description
<VulnDiscussion>When X11 forwarding is enabled, there may be additional exposure to the server and client displays if the sshd proxy display is configured to listen on the wildcard address. By default, sshd binds the forwarding server to the loopback address and sets the hostname part of the "DISPLAY" environment variable to localhost. This prevents remote hosts from connecting to the proxy display.</VulnDiscussion><FalsePositives></FalsePositives><FalseNegatives></FalseNegatives><Documentable>false</Documentable><Mitigations></Mitigations><SeverityOverrideGuidance></SeverityOverrideGuidance><PotentialImpacts></PotentialImpacts><ThirdPartyTools></ThirdPartyTools><MitigationControl></MitigationControl><Responsibility></Responsibility><IAControls></IAControls>
- ID
- SV-258011r943050_rule
- Severity
- Medium
- References
- Updated
Remediation - Manual Procedure
Configure the SSH daemon to prevent remote hosts from connecting to the proxy display.
Add the following line in "/etc/ssh/sshd_config", or uncomment the line and set the value to "yes":
X11UseLocalhost yes