A memory corruption issue was addressed with improved memory handling. This issue is fixed in iOS 15.1 and iPadOS 15.1, macOS Monterey 12.0.1, iOS 14.8.1 and iPadOS 14.8.1, Security Update 2021-007 Catalina, macOS Big Sur 11.6.1. A malicious application may be able to execute arbitrary code with kernel privileges.
http://seclists.org/fulldisclosure/2021/Dec/43
http://seclists.org/fulldisclosure/2021/Dec/44
https://support.apple.com/en-us/HT212867
https://support.apple.com/en-us/HT212868
https://support.apple.com/en-us/HT212869
https://support.apple.com/en-us/HT212871
https://support.apple.com/en-us/HT212872