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.

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Fixes

Solution

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Workaround

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History

Wed, 10 Jun 2026 00:45:00 +0000

Type Values Removed Values Added
First Time appeared Mongodb
Mongodb mongodb Server
Vendors & Products Mongodb
Mongodb mongodb Server

Tue, 09 Jun 2026 22:30:00 +0000

Type Values Removed Values Added
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.
Title Using MaxKey() may crash the server
Weaknesses CWE-617
References
Metrics cvssV3_1

{'score': 6.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'}

cvssV4_0

{'score': 7.1, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N'}


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cve-icon MITRE

Status: PUBLISHED

Assigner: mongodb

Published:

Updated: 2026-06-09T22:10:45.815Z

Reserved: 2026-05-27T17:47:39.152Z

Link: CVE-2026-9749

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-06-09T23:17:04.380

Modified: 2026-06-09T23:17:04.380

Link: CVE-2026-9749

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-06-10T00:30:16Z

Weaknesses