---
id: "CVE-2026-120803"
page: "https://infrastack.ai/live/CVE-2026-120803"
kind: "vulnerability"
aliases: ["CVE-2026-120803"]
title: "MongoDB: window function use-after-free leaks heap memory and can crash the server"
severity: "high"
cvss: 7.1
epss: null
exploited: false
status: "open"
category: "runtime"
products: [{"name": "MongoDB", "fixed": [], "affected": "", "ecosystem": "vendor"}]
ecosystems: ["vendor"]
tags: ["database", "mongodb", "runtime", "self-hosted"]
not_affected_if: ["auth-required", "managed-hosting"]
published_at: "2026-11-10T20:18:50+00:00"
first_seen_at: "2026-11-10T20:46:01+00:00"
updated_at: "2026-11-10T21:03:58+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-120803", "first_seen_at": "2026-11-10T20:46:01+00:00"}, {"source": "analyst", "url": null, "first_seen_at": "2026-11-10T21:03:58+00:00"}]
exploit_sources: []
---

# MongoDB: window function use-after-free leaks heap memory and can crash the server

Link for people: https://infrastack.ai/live/CVE-2026-120803 (this .md is for agents)

A use-after-free in MongoDB's Slot-Based Execution window function accumulator, used by certain $setWindowFields pipelines, lets a stale pointer be read during serialization. An attacker can read adjacent heap contents and crash the mongod server.

_Summary, check and fix written by a model from the sources; labelled as such._

## Affected

- vendor:MongoDB affected range not listed fixed no fixed version listed

## How to check

- Check the running version with `mongod --version` and compare it against the fixed versions in the MongoDB advisory
- Look for pipelines that use `$setWindowFields` if you have application logs or query audit data

## Timeline

- 2026-11-10T20:46:01+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-120803
- 2026-11-10T21:03:58+00:00 analyst — Searched NVD, cve.org, MongoDB alerts page, release notes 8.0/8.3 and web: no MongoDB advisory or Jira entry for this CVE is reachable (NVD/cve.org pages empty). Affected and fixed versions remain unknown; nothing verified. Settle by finding the MongoDB SERVER-xxxxx Jira/CVE record (cna mongodb) or the release notes naming CVE-2026-120803. Interim check: mongod --version and whether  is used; upgrade to latest patch of your release line.

## From the sources

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.

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