Vulnerability Discussion

Terminating an idle session within a short time period reduces the window of opportunity for unauthorized personnel to take control of a management session enabled on the console or console port that has been left unattended. In addition, quickly terminating an idle session will also free up resources committed by the managed network element.

Terminating network connections associated with communications sessions includes, for example, de-allocating associated TCP/IP address/port pairs at the operating system level and de-allocating networking assignments at the application level if multiple application sessions are using a single operating system-level network connection. This does not mean the operating system terminates all sessions or network access; it only ends the inactive session and releases the resources associated with that session.

Satisfies: SRG-OS-000029-GPOS-00010, SRG-OS-000031-GPOS-00012

Check

Verify the operating system initiates a session lock after 15 minutes of inactivity.

Check the value of the system inactivity timeout with the following command:

$ sudo grep -i lock-after-time /etc/tmux.conf

set -g lock-after-time 900

If "lock-after-time" is not set to "900" or less in the global tmux configuration file to enforce session lock after inactivity, this is a finding.

Fix

Configure the operating system to enforce session lock after a period of 15 minutes of inactivity by adding the following line to the "/etc/tmux.conf" global configuration file:

set -g lock-after-time 900