It was discovered that a nft object or expression could reference a nft set on a different nft table, leading to a use-after-free once that table was deleted.
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 Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.