In MongoDB Server 8.0, an aggregation stage can leave its _subPipeline field null during processing of certain pipelines.
Date: 2026-06
Affected: mongodb/mongodb
Attack vector: dos
Category: vulnerability-disclosure
Severity: Medium
CVE: CVE-2026-9743
CWE: CWE-476
CVSS: 6.5 (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H)

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.


Mitigations:

Architectural layers (MAESTRO):