Reachable assertion in MongoDB Server - CVE-2026-9749
Published: August 18, 2026
Vulnerability identifier: #VU144167
CSH Severity: Low
CVSS v4: 6 [CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-9749
CWE-ID: CWE-617
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote user to cause a denial of service.
The vulnerability exists due to reachable assertion in the internal $exchange stage when running an aggregation pipeline using key-range partitioning and order-preserving delivery. A remote user can run a crafted aggregation pipeline to cause a denial of service.
Exploitation requires a single key range to produce enough documents to fill its exchange buffer so that many results are routed to the same consumer.
Affected software
MongoDB Server
How to mitigate CVE-2026-9749
Install security update from vendor's website.
MongoDB Server - addressed in versions 7.0.35, 8.0.24, 8.2.10, 8.3.3