The $internalIndexKey aggregation expression can be used by any authenticated user to crash a MongoDB server (mongod). The expression fails to handle compound wildcard index specifications, triggering an internal consistency check that aborts the server process. The user must be able to run an aggregation pipeline.

An authenticated user with basic write privileges can cause the mongod process to terminate abnormally by sending a crafted transaction command with an incomplete set of required fields. The issue stems from inconsistent validation across related transaction command parameters, resulting in a fatal internal invariant failure and denial of service.

When compute mode is enabled on a standalone mongod instance, insufficient validation of externally sourced BSON data during aggregation pipeline processing can result in memory corruption, potentially leading to process termination or other unintended behavior. This configuration is non-default and requires explicit enablement at startup.

An authenticated user can cause the mongod process to be terminated by the operating system under memory pressure via the $rankFusion and $scoreFusion aggregation stages. The issue originates in the server's error-handling path and requires the ability to run aggregation queries.