A use after free issue was addressed with improved memory management. This issue is fixed in macOS Big Sur 11.6.2, tvOS 15.2, macOS Monterey 12.1, Security Update 2021-008 Catalina, iOS 15.2 and iPadOS 15.2, watchOS 8.3. An application may be able to execute arbitrary code with kernel privileges.
The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.