Quick answers
- Is CVE-2026-120821 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-120821 being exploited in the wild.
- How severe is CVE-2026-120821?
- Medium severity, with a CVSS score of 6.5, published 10 November 2026.
- Which products and versions are affected?
- MongoDB Server before 9.0.7.
- Is there a fix for CVE-2026-120821?
- Yes: fixed in 9.0.7. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-120821 attacked?
- It is attacked over the network, in a software library.
- Am I affected by CVE-2026-120821?
- Check whether you run MongoDB Server at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
How to fix
- Fixed in: 9.0.7
Technical details
A use-after-free vulnerability exists in MongoDB's aggregation framework, specifically in ExpressionSortArray and related expression classes (ExpressionTopN, ExpressionTop, ExpressionBotton, ExpressionBottomN). These classes incorrectly clone the PatternValueCmp member by copying a pointer to a Collator object from the original ExpressionContext; when the original context is destroyed, the pointer becomes dangling. An authenticated user with read privileges can trigger the vulnerability by evaluating certain expressions in an aggregation sub-pipeline, causing a denial of service.
Affected products
- MongoDB Server before 9.0.7
Timeline
- 2026-11-10: disclosed
- 2026-11-10: patched