A memory initialization issue was addressed with improved memory handling. This issue is fixed in iOS 12.1.3, macOS Mojave 10.14.3, tvOS 12.1.2. A malicious application may cause unexpected changes in memory shared between processes.
https://www.exploit-db.com/exploits/46296/
https://support.apple.com/HT209447
https://support.apple.com/HT209446