RHEL 9 must require a unique superusers name upon booting into single-user and maintenance modes.

STIG ID: RHEL-09-212020 |  SRG: SRG-OS-000080-GPOS-00048 |  Severity: high |  CCI:  | Vulnerability Id: V-257789

Vulnerability Discussion

Having a nondefault grub superuser username makes password-guessing attacks less effective.

Check

Configure RHEL 9 to have a unique username for the grub superuser account.

Edit the "/etc/grub.d/01_users" file and add or modify the following lines in the "### BEGIN /etc/grub.d/01_users ###" section:

set superusers="superusers-account"
export superusers

Once the superuser account has been added, update the grub.cfg file by running:

$ sudo grubby --update-kernel=ALL

Fix

Verify the boot loader superuser account has been set with the following command:

$ sudo grep -A1 "superusers" /etc/grub2.cfg

set superusers=""
export superusers

The is the actual account name different from common names like root, admin, or administrator.

If superusers contains easily guessable usernames, this is a finding.