Vulnerability · Published Jun 9, 2026 · Assigned by mongodb
CVE-2026-9749Using MaxKey() may crash the server
Medium 6.5
In plain English
A medium-severity security flaw in MongoDB Server from MongoDB. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 19% of all known vulnerabilities).
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.
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| MongoDB | MongoDB Server | 8.3.0 – before 8.3.38.2.0 – before 8.2.108.0.0 – before 8.0.247.0.0 – before 7.0.35 |
Weakness: CWE-617 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H