Vulnerability Discussion

If an account other than root also has a User Identifier (UID) of "0", it has root authority, giving that account unrestricted access to the entire operating system. Multiple accounts with a UID of "0" afford an opportunity for potential intruders to guess a password for a privileged account.

Check

Check the system for duplicate UID "0" assignments with the following command:

$ sudo awk -F: '$3 == 0 {print $1}' /etc/passwd

If any accounts other than root have a UID of "0", this is a finding.

Fix

Change the UID of any account on the system, other than root, that has a UID of "0".

If the account is associated with system commands or applications, the UID should be changed to one greater than "0" but less than "1000". Otherwise, assign a UID of greater than "1000" that has not already been assigned.