A memory corruption issue was addressed with improved state management. This issue is fixed in macOS Big Sur 11.0.1, iOS 14.2 and iPadOS 14.2, tvOS 14.2, watchOS 7.1. An application may be able to execute arbitrary code with kernel privileges.
http://seclists.org/fulldisclosure/2020/Dec/26
http://seclists.org/fulldisclosure/2020/Dec/32
https://support.apple.com/en-us/HT211928
https://support.apple.com/en-us/HT211929
https://support.apple.com/en-us/HT211930