Apple users have been warned of a serious vulnerability with the latest version of Apple’s operating system, macOS High Sierra, after it was discovered that anyone can potentially gain full access to a machine without requiring a password.
The widely reported vulnerability is exploitable via the authentication dialog box and allows any rogue user with a foothold on a target computer the ability to gain the deepest level of access, known as “root” privileges. The exploit process is simple and can be done by following these steps from admin or guest account:
- Open System Preferences on the machine;
- Select Users & Groups;
- Click the lock icon to make changes;
- Enter “root” in the username field of a login window;
- Move the cursor into the Password field and hit the enter button a few times, leaving it blank.
From there, macOS High Sierra logs the unauthorised user in with root privileges, allowing them access as a “superuser” with permission to read and write to system files, including those in other macOS accounts as well.
Although clearly a very serious issue, anyone seeking to exploit this vulnerability would need physical access to the target machine. Apple have urgently rushed out a patch to address this issue and we strongly encourage Mac users to update their OS at their earliest opportunity. Details of the update are available via the following support page: https://support.apple.com/en-us/HT208315
If unable to update immediately, users should mitigate the vulnerability by ensuring unattended devices are locked and by carefully monitoring any remote desktop access controls. To manually mitigate the risk, Mac users should also enable the root user with a password to prevent the account from being accessed with a blank password.