A buffer overflow was addressed with improved size validation. This issue is fixed in macOS Big Sur 11.4, tvOS 14.6, watchOS 7.5, iOS 14.6 and iPadOS 14.6. An application may be able to execute arbitrary code with kernel privileges.
https://support.apple.com/en-us/HT212533
https://support.apple.com/en-us/HT212532