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.
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
| Product | Fixed in | Fix | Released |
|---|---|---|---|
| Windows apps | |||
| MongoDB | 8.3.3 | MongoDB 8.3.3 | May 28, 2026 |
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