CVE-2026-120803: MongoDB SBE $locf Window Accumulator Use-After-Free Enables Heap OOB Read and Server Crash
Advisory generated from the CVE record, CISA, Exploit Observer and VEDAS: what it is, whether it is exploited, who is affected, and how to fix and detect it.
Generated by VEDAS. Scores as of 2026-11-11 15:49 UTC. Rebuilt every few hours from cve-scores, CISA KEV and vedas-signatures. How this works and its limits.
What it is
A use-after-free issue exists in MongoDB’s 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.
Description quoted from the CVE record (assigned by mongodb, published 2026-11-10).
Weakness: CWE-416: Use After Free
How it can be exploited
Exploitable over the network with low attack complexity with no special attack requirements needing low privileges and no user interaction. Impact: confidentiality low, integrity none, availability high. CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:N/VA:H/SC:N/SI:N/SA:N
Public exploit evidence (Exploit Observer)
Exploit Observer has no public exploit code naming this CVE. Check Exploit Observer for anything new.
Live scores
- EPSS
- 0.004
low predicted chance of attack - VEDAS
- 0.048
little exploit evidence - On CISA KEV
- Not listed
- Detection rule
- No public rule yet
Who is affected
| Product | Affected | Not affected |
|---|---|---|
| MongoDB Server | from 9.0.0 before 9.0.7 from 8.3.0 before 8.3.16 | Not stated |
Version ranges exactly as the CVE record states them. “Before X” means X is the first fixed version.
How to fix it
Fixed versions stated in the CVE record: 9.0.7, 8.3.16.
How to detect it
There is no open VEDAS detection rule for this bug yet. It is listed on the detection gaps page if CISA has confirmed attacks.
Advisories on this CVE
References
Other references
Other databases
Where this comes from
This advisory is generated automatically by VEDAS from: CVE.org record, cve-scores (EPSS and VEDAS), Exploit Observer. Text in quotes is reproduced from the source; everything else is a fixed template filled with source fields. Nothing here is written by a language model. Check the vendor advisory before acting, and read how VEDAS and Exploit Observer work, and their limits.
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