CVE-2026-9749 Using MaxKey() may crash the server
An attacker can crash the MongoDB server by triggering a specific aggregation pipeline condition involving key-range partitioning and buffer overflow.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-9749?
CVE-2026-9749 is a high-severity denial of service vulnerability in Mongodb Mongodb, published on 9 Jun 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
This issue can occur when running an aggregation pipeline that uses the internal $exchange stage configured with key-range partitioning and order-preserving delivery. If a single key range produces enough documents to fill its exchange buffer (that is, many results are routed to the same consumer), the server reaches the code path where a full per-consumer buffer is detected but the internal "high watermark" for that key range is not updated as intended.
Weakness: CWE-617
Which versions are affected by CVE-2026-9749?
1 open source package ship an affected version, including mongodb. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
mongodb Bitnami | From 7.0.0 | 7.0.35, 8.0.24, 8.2.10, 8.3.3 |
Products include Mongodb Mongodb.
How do I fix CVE-2026-9749?
Upgrade mongodb to a fixed version for your release line: 7.0.35, 8.0.24, 8.2.10 or 8.3.3.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-9749 being exploited?
There is no known exploitation of CVE-2026-9749 in the wild and no public exploit code.
Other vulnerabilities in Mongodb Mongodb
- CVE-2025-14847 MongoDB and MongoDB Server Improper Handling of Length Parameter Inconsistency
- CVE-2026-82067 Auth bypass in MongoDB Server
- CVE-2026-13072 MongoDB Improper Input Validation in Compute Mode External Data Processing Leading to Memory Corruption
- CVE-2017-15535 Denial of service in n/a
- CVE-2026-18691 Improper Authentication in MongoDB Intra-Cluster Connections Allows Credential Exposure
Sources
Also known as BIT-mongodb-2026-9749, GHSA-ppxc-fr36-g8v9, MINI-6m66-2885-jqwv, MINI-chjj-jh23-m5pq, MINI-fgpj-6mx8-5r5x, MINI-jqfv-jrqw-gfjj and 1 more.