A recent macOS Mojave security patch might make your Mac slow to a crawl

Last week alongside macOS Catalina 10.15.7, Apple released a security patch for macOS Mojave that many users found has caused their computer to slow to a crawl. This hasn’t affected everyone universally, as with most bugs, so it took a few days for people to figure out what was going on. Your computer has to meet a few very certain circumstances for this to be a problem. Normally these security patches do not cause these sorts of problems, but Apple has pulled this update to prevent more people from having this problem and will likely re-release it soon with a fix.

However, if your computer has inexplicably slowed, is beachballing/pinwheeling way more than normal, or basically completely stopped in the past few days, this is a pretty easy fix if you know what to do.

This bug only affects macOS Mojave 10.14.6. To see what version of macOS you are running click the Apple logo in the top left corner of your screen and choose “About This Mac…”

Option 1: Upgrade to macOS Catalina

This problem doesn’t affect macOS Catalina. So if you were planning to upgrade to Apple’s latest system software anyway, this will take care of the problem. You can download the upgrade in the Mac App Store.

‎macOS Catalina
‎macOS Catalina
Developer: Apple
Price: Free

Option 2: Reinstall macOS Mojave

This isn’t as difficult as it sounds.

  1. Turn your Mac completely off
  2. Press and release the power button then immediately press and hold two keys on your keyboard: “Command” + “R”
  3. Keep holding those two keys until you see the Apple logo.
  4. Once you see the screen for macOS Recovery, choose the option to Reinstall macOS and click “Continue”. This will not erase anything from your computer, it will simply slip a new copy of your current macOS system software underneath of your data.
  5. Click continue, agree, choose your hard drive, and follow the prompts to unlock your drive using your computer start-up password if prompted. Each person will see slightly different things here depending on how your computer is set up specifically but just follow the prompts.
  6. Wait for your computer to reinstall, which can take anywhere from 20 minutes to a few hours depending on the speed of your Mac and of your internet connection.

Option 3: Upgrade to macOS Catalina via Recovery Mode

If you want to upgrade to macOS Catalina, but your computer is running too poorly to do so because of this bug, you can follow the steps above to reinstall macOS Mojave. But on step 2, the keys you want to press are “Command” + “Option” + “R”. This will instruct your computer to use the latest system software rather than your current system software. You will be prompted to connect to your WiFi network during computer startup.

Further help

If you are an existing customer who needs help with this or if you have other questions, or if you are in San Francisco and interested in becoming a client I invite you to book an appointment with me. Otherwise, you may wish to contact Apple Support or to find a local Apple consultant.