RHEL 9 must terminate idle user sessions.

STIG ID: RHEL-09-412080  |  SRG: SRG-OS-000163-GPOS-00072 | Severity: medium |  CCI: CCI-001133

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.

Check

Verify that RHEL 9 logs out sessions that are idle for 15 minutes with the following command:

$ sudo grep -i ^StopIdleSessionSec /etc/systemd/logind.conf

StopIdleSessionSec=900

If "StopIdleSessionSec" is not configured to "900" seconds, this is a finding.

Fix

Configure RHEL 9 to log out idle sessions by editing the /etc/systemd/logind.conf file with the following line:

StopIdleSessionSec=900

The "logind" service must be restarted for the changes to take effect. To restart the "logind" service, run the following command:

$ sudo systemctl restart systemd-logind

Note: To preserve running user programs such as tmux, uncomment and/or edit "KillUserProccesses=no" in "/etc/systemd/logind.conf".
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