X displays must not be exported to the world.

From Oracle Linux 5 Security Technical Implementation Guide

Associated with: CCI-000225

SV-63295r1_rule X displays must not be exported to the world.

Vulnerability discussion

Open X displays allow an attacker to capture keystrokes and to execute commands remotely. Many users have their X Server set to "xhost +", permitting access to the X Server by anyone, from anywhere.

Check content

If Xwindows is not used on the system, this is not applicable. Check the output of the "xhost" command from an X terminal. Procedure: # xhost If the output reports access control is enabled (and possibly lists the hosts able to receive X window logins), this is not a finding. If the xhost command returns a line indicating access control is disabled, this is a finding. Note: It may be necessary to define the display if the command reports it cannot open the display. Procedure: $ DISPLAY=MachineName:0.0; export DISPLAY MachineName may be replaced with an Internet Protocol Address. Repeat the check procedure after setting the display.

Fix text

If using an xhost-type authentication the "xhost -" command can be used to remove current trusted hosts and then selectively allow only trusted hosts to connect with "xhost +" commands. A cryptographically secure authentication, such as provided by the xauth program, is always preferred. Refer to your X11 server's documentation for further security information.

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