MongoDB Server: Use-after-free in aggregation sub-pipelines
Summary
A use-after-free vulnerability in the aggregation framework of MongoDB Server can occur when certain expressions are evaluated in an aggregation sub-pipeline. An authenticated user with read privileges can trigger it, and the server may terminate unexpectedly. According to the CVSS vector, the impact is limited to availability; confidentiality and integrity are not affected.
Affected
- MongoDB Server 9.0.0 to before 9.0.7
- Other branches (8.x, 7.x and older): Unknown.
Fixed in
- Fixed in MongoDB Server 9.0.7.
Workaround
- No vendor workaround known.
- An unofficial suggestion is to restrict access to trusted users and monitor for unexpected server terminations while patching is pending.
Exploitation
- No evidence of exploitation in the wild found; CISA KEV status not verified.
- No public proof of concept found.
Our recommendation
- Upgrade MongoDB Server to 9.0.7 or later, as part of the broader security release.
- Until patched, review accounts with read privileges and restrict network access to MongoDB, especially from untrusted networks.
- Check whether other MongoDB branches are in use and verify their status in the MongoDB advisory.
- Monitor logs for unexpected server restarts.
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- MongoDB Jira ticket SERVER-136285 jira.mongodb.org
- CVE-2026-120821 record summary (threatint) cve.threatint.com
- CVE-2026-120821 on OffSeq Radar radar.offseq.com
- CVE-2026-120821 on Strix AI www.strix.ai
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, 07:05.
Original description (NVD)
A use-after-free in the aggregation framework of MongoDB Server can occur when certain expressions are evaluated in an aggregation sub-pipeline. The condition can be caused by an authenticated user with read privileges, and may result in the server terminating unexpectedly.
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.
Affected? We can help.
We check whether your systems are affected, install updates and close the gap – continuously with the System Health Checker if you wish.