An authenticated user may trigger a use after free that may result in MongoDB Server crash and other unexpected behavior, even if the user does not have authorization to shut down a server. The crash is triggered on affected versions by issuing an aggregation framework operation using a specific combination of rarely-used aggregation pipeline expressions. This issue affects MongoDB Server v6.0 version prior to 6.0.21, MongoDB Server v7.0 version prior to 7.0.17 and MongoDB Server v8.0 version prior to 8.0.4 when the SBE engine is enabled.
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 Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.