A memory corruption issue was addressed with improved lock state checking. 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/46299/
https://support.apple.com/HT209447
https://support.apple.com/HT209446
https://support.apple.com/HT209443
http://www.securityfocus.com/bid/106695
http://packetstormsecurity.com/files/156051/XNU-vm_map_copy-Insufficient-Fix.html