Vulnerability Discussion

Setting the most restrictive default permissions ensures that when new accounts are created, they do not have unnecessary access.

Check

Verify Ubuntu 24.04 LTS defines default permissions for all authenticated users in such a way that the user can read and modify only their own files with the following command:

$ grep -i '^\s*umask' /etc/login.defs
UMASK 077

If the "UMASK" variable is set to "000", this is a finding with the severity raised to a CAT I.

If the value of "UMASK" is not set to "077", is commented out, or is missing, this is a finding.

Fix

Configure the system to define the default permissions for all authenticated users in such a way that the user can read and modify only their own files.

Edit the "UMASK" parameter in the "/etc/login.defs" file to match the example below:

UMASK 077