A use-after-free vulnerability can be triggered in sharded clusters by an authenticated user with the read role who issues a specially crafted $lookup or $graphLookup aggregation pipeline.
Weakness
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 Any operations using the original pointer are no longer valid because the memory “belongs” to the code that operates on the new pointer.