An out-of-bounds read was addressed with improved bounds checking. This issue is fixed in macOS Big Sur 11.0.1, watchOS 7.0, tvOS 14.0, iOS 14.0 and iPadOS 14.0. An application may be able to read restricted memory.
http://seclists.org/fulldisclosure/2020/Dec/26
http://seclists.org/fulldisclosure/2020/Dec/32
https://support.apple.com/en-us/HT211843
https://support.apple.com/en-us/HT211844
https://support.apple.com/en-us/HT211850