Impact: A remote attacker may be able to cause unexpected application termination or arbitrary code execution
Description: An out-of-bounds read was addressed with improved input validation.
CVE-2019-8641: Samuel Groß and Natalie Silvanovich of Google Project Zero
The update is for iOS 12 devices that cannot upgrade to iOS 13, macOS Mojave 10.14.6, macOS High Sierra 10.13.6, and macOS Sierra 10.12.6.
How to install the iOS 12.4.2 update
Back up your device first. You also need an internet connection.
Open the Settings app and tap on General. Then tap Software Update. The device will check for the update and once it is found you can tap Download and Install to proceed.
How to install the update on a Mac
Before installing any operating system update, it's a good idea to back up your Mac. The download and installation will take several minutes.
When you're ready to install the update, click on the Apple menu and select About This Mac. Then click on the Software Update button. On Mojave, the Software Update system preference will open and look for the update. Once it's located, you can proceed with the installation. On High Sierra and Sierra, the App Store app will launch and it will look for the update. The update will appear in the Updates section.