Vulnerability Discussion

Previous versions of software components that are not removed from the information system after updates have been installed may be exploited by adversaries. Some information technology products may remove older versions of software automatically from the information system.

Check

Verify APT is configured to remove all software components after updated versions have been installed by using the following command:

$ grep -i remove-unused /etc/apt/apt.conf.d/50-unattended-upgrades
Unattended-Upgrade::Remove-Unused-Kernel-Packages "true";
Unattended-Upgrade::Remove-Unused-Dependencies "true";

If "Unattended-Upgrade::Remove-Unused-Kernel-Packages" and "Unattended-Upgrade::Remove-Unused-Dependencies" are not set to "true", are commented out, or are missing, this is a finding.

Fix

Configure APT to remove all software components after updated versions have been installed.

Add or modify the following lines in the "/etc/apt/apt.conf.d/50-unattended-upgrades" file:

Unattended-Upgrade::Remove-Unused-Kernel-Packages "true";
Unattended-Upgrade::Remove-Unused-Dependencies "true";