CVE-2026-104005: Incorrect authorization in MongoDB Server router for bulk writes to system namespaces
A security issue was discovered in MongoDB mongos (the sharded cluster router) where an authenticated user with readWrite privileges could crash the mongos process by crafting a specially formed aggregation pipeline. The issue leverages an internal aggregation stage that lacks proper authorization checks despite being intended for internal use, allowing a subsequent stage to be forced to execute on the router under conditions it was not designed to handle. This results in an unhandled fatal error that causes the mongos process to immediately abort, resulting in denial of service for all clients routed through the affected mongos instance.
Other sources
Incorrect authorization in the write routing component of the MongoDB Server sharded cluster router can cause bulk write operations to skip authorization checks for the target namespace. An authenticated user with write privileges on a regular collection who submits a bulk write that targets an internal system namespace may have the operation accepted by the router even though they are not authorized to write to that namespace. The resulting impact depends on the system namespace targeted.
— MITRE
Affected Software
Event History
Frequently Asked Questions
Which deployments are exposed?
The issue is in the write routing component of a MongoDB Server sharded cluster router. The provided information does not indicate that non-sharded deployments are affected.
What access does an attacker need?
An attacker must be authenticated and have write privileges on a regular collection. They must submit a bulk write targeting an internal system namespace.
What is the potential impact?
The router may accept a write to an internal system namespace without enforcing authorization for that namespace. The resulting impact depends on which system namespace is targeted.