CVE-2026-9747: Crafted cross-shard merge aggregation crashes MongoDB Server
Adding fromRouter:true and runtimeConstants.userRoles could cause aggregations to crash mongodb server.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Compensating control
Reject, sanitize, or otherwise block aggregation requests that include the fields fromRouter:true or runtimeConstants.userRoles (e.g., at the application layer, API gateway, or mongos proxy) to prevent crafted cross-shard merge aggregations from crashing the MongoDB server.
- Operational
If a MongoDB server crashes due to this issue, restart the affected mongod/mongos instances, collect server logs and crash dumps for analysis, and review recent aggregation requests for presence of fromRouter:true or runtimeConstants.userRoles.
Event History
Frequently Asked Questions
What is the severity of CVE-2026-9747?
CVE-2026-9747 has a severity rating of medium, with a score of 6.5.
What impact does CVE-2026-9747 have on MongoDB Server?
CVE-2026-9747 can lead to crashes of the MongoDB Server during crafted cross-shard merge aggregations.
How do I mitigate CVE-2026-9747?
To mitigate CVE-2026-9747, avoid using fromRouter:true in aggregations until a patch is applied.
What versions of MongoDB are affected by CVE-2026-9747?
CVE-2026-9747 affects certain versions of MongoDB Server that utilize fromRouter:true and runtimeConstants.userRoles in aggregations.
Is there a patch available for CVE-2026-9747?
Yes, a patch is expected to be released to address CVE-2026-9747, so check for updates from MongoDB.