MongoDB SBE Engine Use-After-Free Read via $unwind on Time-Series
CVE-2026-120809 Published on November 10, 2026
Heap use-after-free read via yield-time state save in time-series block unpacking
A use-after-free read issue exists in MongoDBs SBE (Slot-Based Execution) engine when processing aggregation pipelines with $unwind on time-series collections. An internal error in state-preservation logic can cause a value still referenced by downstream stages to have its underlying memory freed prematurely. An authenticated user can craft an aggregation pipeline under specific conditions to trigger this condition, potentially reading recycled server heap memory in query results or crashing the server. This issue is only triggerable when a non-default server parameter related to the SBE engine is enabled.
Vulnerability Analysis
CVE-2026-120809 can be exploited with network access, and requires small amount of user privileges. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have no impact on confidentiality and integrity and availability.
Weakness Type
What is a Dangling pointer Vulnerability?
Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code.
CVE-2026-120809 has been classified to as a Dangling pointer vulnerability or weakness.
Products Associated with CVE-2026-120809
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Affected Versions
MongoDB Server:- Version 9.0.0 and below 9.0.7 is affected.
- Version 8.3.0 and below 8.3.16 is affected.
- Version 8.0.0 and below 8.0.37 is affected.
Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.