MongoDB SBE window function use-after-free (CVE-2026-120803)
CVE-2026-120803 Published on November 10, 2026
MongoDB SBE $locf Window Accumulator Use-After-Free Enables Heap OOB Read and Server Crash
A use-after-free issue exists in MongoDBs SBE (Slot-Based Execution) implementation of a window function accumulator used by certain $setWindowFields aggregation pipelines. Under specific conditions, the accumulator can retain a dangling pointer to memory that has since been freed. When this stale pointer is later dereferenced during serialization of the carried-forward value, it can result in a heap out-of-bounds read that may expose adjacent heap contents and crash the mongod server. An authenticated user with readWrite privileges on a database can trigger this issue by crafting a specific aggregation pipeline.
Vulnerability Analysis
CVE-2026-120803 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-2026-120803 has been classified to as a Dangling pointer vulnerability or weakness.
Products Associated with CVE-2026-120803
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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.
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.