A buffer overflow was addressed with improved bounds checking. This issue is fixed in iOS 12.1.3, macOS Mojave 10.14.3, tvOS 12.1.2, watchOS 5.1.3. An application may be able to execute arbitrary code with kernel privileges.
https://www.exploit-db.com/exploits/46300/
https://support.apple.com/HT209448
https://support.apple.com/HT209447
https://support.apple.com/HT209446