MongoDB SBE: $lookup Auth Query Can Trigger Double-Free/UAF
CVE-2026-4358 Published on March 17, 2026
Memory safety issues in slot-based execution hash table spill
A specially crafted aggregation query with $lookup by an authenticated user with write privileges can cause a double-free or use-after-free memory issue in the slot-based execution (SBE) engine when an in-memory hash table is spilled to disk.
Vulnerability Analysis
CVE-2026-4358 is exploitable with network access, and requires small amount of user privileges. This vulnerability is consided to have a high level of attack complexity. The potential impact of an exploit of this vulnerability is considered to have a small impact on confidentiality and integrity, and a high impact on availability.
Weakness Type
What is a Double-free Vulnerability?
The product calls free() twice on the same memory address, potentially leading to modification of unexpected memory locations. When a program calls free() twice with the same argument, the program's memory management data structures become corrupted. This corruption can cause the program to crash or, in some circumstances, cause two later calls to malloc() to return the same pointer. If malloc() returns the same value twice and the program later gives the attacker control over the data that is written into this doubly-allocated memory, the program becomes vulnerable to a buffer overflow attack.
CVE-2026-4358 has been classified to as a Double-free vulnerability or weakness.
Products Associated with CVE-2026-4358
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Affected Versions
MongoDB Inc MongoDB Server:- Version 8.2 and below 8.2.6 is affected.
- Version 8.0 and below 8.0.20 is affected.
- Version 7.0 and below 7.0.31 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.