# CVE-2026-9749: Using MaxKey() may crash the server

CVE-2026-9749 is fixed in MongoDB on 1 platform by MongoDB 8.3.3 (version 8.3.3), released May 28, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-9749
- Priority: High
- CVSS: 7.1
- EPSS: 0.0027
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Jun 9, 2026
- Weakness: CWE-617: Reachable assertion
- Vendor advisory: https://nvd.nist.gov/vuln/detail/CVE-2026-9749

## 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Windows apps | MongoDB | 8.3.3 | [MongoDB 8.3.3](https://patchblox.com/security/data/fix/windows-app/mongodb.server-8.3.3.md) | May 28, 2026 |

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Data as of 2026-11-08T00:53:09Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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