Login as root on MacOs High Sierra — security vulnerability

If you’re using MacOs High Sierra (v10.13.1, maybe also other versions) you’re probably exposed to a very dangerous security vulnerabily which allows anyone, with a physical access to your machine, to login as the root user. This bug was discovered today by Lemi Orhan Ergin, a developer that promptly contacted Apple Support to ask about this issue.

Who is vulnerable?

Everyone who haven’t disabled the guest user account and didn’t change the default root password in MacOs High Sierra.

How can i test this issue on my Mac?

Just try to login to your Mac using root as username and leave the password field blank. If you’re (un)lucky, you’ll can login to the system as root after pressing the login button several times. The same issue could be tested in System Preferences > Users & Groups after enabling edits. Try to login as root user with a blank password:

How can i prevent my system to be hacked?

If you can’t wait for an official fix, you can use some workarounds to keep your system safe:

1 — Disable guest users access: go to System Preferences > Users & Groups > Guest User and uncheck Allow guests to log in to this computer.

2 — Change the root user password: go to System Preferences > Users & Groups > Login Options, then select Join > Open Directory Utility. Click on the lock and enter your root credentials. Now, you can click on Change Root Password from Edit in menu bar.

Hope it helps… and thanks to Lemi Orhan Ergin for his work! See ya!

UPDATES:

Apple has already fixed this issue. Here you can find a very interesting article that explains in depth the causes of the vulnerability: https://objective-see.com/blog/blog_0x24.html.