A newly discovered bug in macOS High Sierra enables the root superuser on a Mac with a blank password and no security check, essentially giving anyone full access to your Mac.

Apple is likely already working on a fix, but in the meantime, there's a temporary workaround -- enabling the root user with a password. Here's how:

  1. Open Spotlight and search for Directory Utility. directory utility spotlight
  2. Double click on the app result to open.
  3. Click on the lock at the bottom of the window to make changes and enter your username and password for an administrator account on your computer. directory utility
  4. In the menu bar at the top of the screen, choose "Edit." macoshighsierrarootbugeditmenu
  5. Select "Enable Root User."

From there, you can enter a password for the root user account, which prevents it from being accessed with a blank password, which is what the current bug allows to happen.

macoshighsierrarootbugpassword
Disabling the root user account again follows the same steps, but at the "Edit" portion of the process, you'll select "Disable Root User" to remove the option. Until the bug is fixed, though, you'll want to leave the root user account intact to prevent it from being accessed without a password.

To further protect your Mac, you can also disable guest accounts, though this is not a necessary step with a root password enabled. Guest accounts can be disabled by going to System Preferences > Users & Groups and choosing "Guest User" after entering your admin password. Disable "Allow guests to log in to this computer."

Update: Apple has released a security update to fix this issue, and all macOS High Sierra users should apply the update as soon as possible to ensure they are protected.

Related Forum: macOS High Sierra

Top Rated Comments

poppy10 Avatar
87 months ago
This is such a fundamental and major security flaw, it's mind-blowing how it managed to get through Apple's QA

A critical vulnerability that allows root access to all macs with a single click. We'd be laughing at Microsoft if this had occurred with Windows
Score: 27 Votes (Like | Disagree)
rpmurray Avatar
87 months ago
Now the new backdoor that Apple added for the government has been blown.
Score: 12 Votes (Like | Disagree)
Sefstah Avatar
87 months ago
Or, you know, don't leave your laptop sitting around unlocked. As more or less 100% of your critical info is under your user account anyway, probably even in the easy to find Documents folder, it's almost useless to spend time (as a theif) monkeying with root accounts. Just yoink what you need directly. Creating a root password (as a theif) presumes future access to the Mac, in which case it's been lifted already, and there are ways to get at your info, anyway, if it's unencrypted, as most Macs are.

Pretty dumb flaw, yes, but you deserve what you get if you leave your unattended, unlocked laptop lying around where people can physically get at it in the first place.
Laptop? How about all the schools and Universities that use iMacs with admin accounts? This is a HUGE flaw and shouldn’t be downplayed.
Score: 9 Votes (Like | Disagree)
KvR Avatar
87 months ago
Much easier (if your comfortable with the terminal) fix:

sudo passwd root

Just set a password on your root account.
Score: 8 Votes (Like | Disagree)
miniyou64 Avatar
87 months ago
Unbelievable. This is not Steve’s Apple.
Score: 5 Votes (Like | Disagree)
Doctor Q Avatar
87 months ago
A faster way to launch Directory Utility is to type "directory utility" in Spotlight, then press return. (This assumes that you have "Applications" enabled in Spotlight's preferences.)

Make sure you choose a secure root password. Leaving root enabled with an easily guessed password defeats the purpose.
Score: 5 Votes (Like | Disagree)

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