MongoDB Server: Denial of service via uncontrolled memory use in aggregation
Summary
MongoDB Server's aggregation framework exposes an internal expression, $_internalKeyStringValue, to all authenticated clients despite its internal naming. An authenticated user with read privileges can send crafted aggregate commands over several concurrent connections, causing unbounded memory allocation. This can exhaust server memory so that the operating system's out-of-memory killer terminates the mongod process, causing an outage for connected applications.
Affected
- MongoDB Server 9.0.0 to before 9.0.7
- MongoDB Server 8.3.0 to before 8.3.16
- MongoDB Server 8.0.0 to before 8.0.37
- MongoDB Server 7.0.0 to before 7.0.48
- Default configuration: unaffected (per CVE record)
- Versions 6.0 and older: not listed; verify with the vendor advisory
Fixed in
- 9.0.7
- 8.3.16
- 8.0.37
- 7.0.48
Workaround
No vendor-documented workaround known. Interim measures (not vendor guidance): restrict read roles to necessary accounts and limit network access to mongod to application hosts.
Exploitation
No evidence of exploitation in the wild or public proof of concept found at the time of research. CISA KEV status: not checked.
Our recommendation
- Identify all MongoDB 7.0, 8.0, 8.3 and 9.0 instances and confirm their versions.
- Plan upgrades to the fixed releases, prioritising instances reachable beyond the internal network and those with many read-role accounts.
- Restrict network access to mongod and review accounts holding read roles.
- Monitor for unexpected mongod restarts or memory growth.
- Review the MongoDB Jira ticket and release notes to confirm the fix contents.
- CVSS 4.0 base score 7.1 (HIGH); CVSS 3.1 score 6.5 per CNA.
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- CVE Record CVE-2026-120810 www.cve.org
- MongoDB Jira ticket SERVER-132430 jira.mongodb.org
- Vulners PT-2026-120810 vulners.com
- Threat Intelligence CVE-2026-120810 cve.threatint.com
Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 11 Nov 2026, 07:08.
Original description (NVD)
An issue in MongoDB server’s aggregation framework allows an authenticated user with read privileges to cause a denial of service by sending specially crafted aggregate commands using an internal expression. Despite its internal naming, this expression is registered as accessible to any authenticated client. By supplying crafted input parameters across multiple concurrent connections, each evaluation triggers unbounded memory allocations with no per-expression memory limits enforced. This can exhaust available server memory and cause the mongod process to be terminated by the operating system’s out-of-memory killer.
NVD references (1)
Sources
The tracker combines official, freely usable data sources – updated continuously:
- NVD (NIST) – CVEs, rating (CVSS), affected products
- CISA KEV – vulnerabilities confirmed by CISA as actively exploited
- CISA Vulnrichment – CISA assessment (SSVC) in the official CVE record
- FIRST EPSS – probability of exploitation
- Microsoft MSRC – Patch Tuesday: vulnerabilities, severity, updates
- PoC-in-GitHub – public proof-of-concept repositories
- Metasploit (Rapid7) – modules of the Metasploit Framework
- Exploit-DB (OffSec) – archive of public exploits (links only)
- Patch days: official vendor pages (linked per vendor) (Vendor patch days)
This product uses data from the NVD API but is not endorsed or certified by the NVD. EPSS data © FIRST.org.
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