MongoDb NULL Pointer Dereference Vulnerability - CVE-2026-9743

In MongoDB Server 8.0 an aggregation stage can leave its _subPipeline field null during processing of certain pipelines. If a getMore is subsequently issued on the same cursor the server may dereference this null sub-pipeline when reattaching to the operation context accessing an invalid address and crashing the process. This issue allows an authenticated user who can run aggregation pipelines to cause a denial of service by issuing a specially crafted aggregation followed by getMore on affected versions.