Ubuntu 22.04 LTS 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-260530r991589_rule
- Severity
- Medium
- References
- Updated
Remediation - Manual Procedure
Configure the SSH server to prevent remote hosts from connecting to the proxy display.
Add or modify the following line in the "/etc/ssh/sshd_config" file:
X11UseLocalhost yes