ALMA-09-021470 - AlmaLinux OS 9 SSH daemon must disable remote X connections for interactive users.

Information

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.

Solution

Configure the SSH daemon to not allow X11 forwarding.

Add the following line to "/etc/ssh/sshd_config", or uncomment the line and set the value to "no":

X11forwarding no

Alternatively, add the setting to an include file if the line "Include /etc/ssh/sshd_config.d/*.conf" is found at the top of the "/etc/ssh/sshd_config" file:

$ echo 'X11forwarding no' > /etc/ssh/sshd_config.d/40-x11forwarding.conf

Restart the SSH daemon for the settings to take effect:

$ systemctl restart sshd.service

Item Details

Audit Name: DISA Cloud Linux AlmaLinux OS 9 STIG v1r6

Category: CONFIGURATION MANAGEMENT

Plugin: Unix

Control ID: 9677ae7e34370b7b2807027230d0e046241478d1dcde4e01fac52c79c762890f

Detections

Analytics

ALMA-09-021470 - AlmaLinux OS 9 SSH daemon must disable remote X connections for interactive users.

Information

Solution

See Also

Item Details