The macOS High Sierra Root Bug Explained! Rev. 2.0

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The Internet is abuzz with the shocking revelation that now everyone can hack an Apple computer… as long as it’s using the latest macOS High Sierra operating system. Let us explain what’s going on, and share with you the workaround for the macOS High Sierra root bug.

The macOS High Sierra Root Bug Explained

Updated @ 2017-11-30 : Added a new section on the Apple bug fix (Security Update 2017-001) [1], and additional information on the root bug [2].

Originally posted @ 2017-11-29


What Is Root User?

If you are the primary user of a MacOS X system, you have an administrator account with administrator privileges. This gives you more privileges and access than a standard user account. However, that is not the highest access level possible.

There is a Mac superuser account called “root” that gives you elevated read and write privileges to hidden or protected areas of the system. With the Mac root user account, you can even access files in other user accounts.

The Mac OS Root User Login & Password Guide

In fact, it gives you such God-like powers, you can modify or even delete critical system files. In fact, a Mac root user can use the rm -rf * command to delete the contents of every mounted drive in the computer, until macOS crashes when a crucial file or folder is deleted.

So this Mac root user account should only remain disabled unless you really, REALLY need to use it.

Suggested Reading : The Mac Root User Login & Password Guide


The macOS High Sierra Root Bug Updated!

On Tuesday, 28 November 2017, Turkish software developer Lemi Orhan Ergin revealed the macOS High Sierra root bug. With a few simple steps, anyone can gain elevated root user privileges in any computer running macOS High Sierra! Here is a summary of what we know about the root bug :

  1. The root bug exploit requires a computer running macOS High Sierra, with multiple user accounts.
  2. When prompted for a username and password, use these steps to gain root user access without any password :
    • Type “root” as the username and leave the password field blank.
    • Just click “Unlock” twice.
  3. The root bug cannot be exploited remotely, unless screen sharing is enabled.
  4. The root bug was introduced in macOS High Sierra 10.13.1. Earlier versions of macOS were not affected.
  5. Apple confirmed that the bug was due to “a logic error… in the validation of credentials“.
  6. Apple also confirmed that the bug would allow an attacker to “bypass administrator authentication without supplying the administrator’s password“.
  7. Several security researchers successfully replicated the bug.


How Serious Is This Root Bug?

The macOS High Sierra root bug is EXTREMELY serious, because it allows a hacker to easily bypass all of the macOS operating system’s security protections.

It doesn’t matter if you encrypted your computer, and secured it with an extremely long and complex password. Anyone who gains root user privileges using this bug can access (read, copy or move) the files in any user account (even those of an administrator) without knowing the password.

What’s even more troubling is that the root bug works even with a disabled root user account. This means the vast majority of Apple computers running on High Sierra are compromised, as the root user account is disabled by default.


How To Fix The Root Bug?

Unlike other security researchers, Lemi Orhan Ergin did not forewarn Apple before publicly revealing the bug, on Twitter no less. He basically exposed a zero-day vulnerability for hackers to use, while Apple rushes to fix the bug.

1. Install macOS Security Update 2017-001 New!

Apple just released Security Update 2017-001. This update will remove the root bug and improve credential validation. INSTALL THIS UPDATE NOW!

Note : This bug fix will reset and disable the root user account.  If you need to use the root user account, you will need to re-enable it, and change its password, after applying the update.

Note : Apple rushed out this update so quickly that they accidentally used a space instead of the version number. You can read more about this in our article – Apple Rushed Out macOS Root Bug Fix & It Shows…

The macOS High Sierra Root Bug Explained

This is not an issue if you are downloading the patch through the App Store. But if you’re applying the patch via Terminal, you need to add a space.

softwareupdate -i “Security Update 2017-001- “

2. Enable Root User With Your Own Password

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If you cannot apply Apple’s bug fix yet, you can block this root bug by enabling the root user account, and setting a password for it.

It’s not so straightforward, so we created a step-by-step guide for you – The Mac Root User Login & Password Guide.

3. Use Additional Encryption

Alternatively, you can opt to move your sensitive data to encrypted containers or drives using third-party encryption utilities like VeraCrypt. Hackers may use the High Sierra root bug to gain access to the encrypted containers or drives, but without the correct password, the actual data won’t be accessible.

4. Physically Protect Your Apple Computer

The good news is the High Sierra root bug generally requires physical access to your Apple computer. Until this bug is fixed, you should make sure your Apple computer is never left unsupervised.

Keep it in a locked room or bag, whenever you are not using it. If no one can get to it, they cannot use the bug to gain root access.

5. Disable Screen Sharing

The High Sierra root bug can be exploited remotely if Screen Sharing is enabled. So make sure you disable Screen Sharing.

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