---
id: "CVE-2026-109503"
page: "https://infrastack.ai/live/CVE-2026-109503"
kind: "vulnerability"
aliases: ["CVE-2026-109503"]
title: "Microsoft Word: double free lets an attacker run code over a network"
severity: "high"
cvss: 8.8
epss: null
exploited: false
status: "open"
category: "package"
products: [{"name": "Microsoft Office Word", "fixed": ["2610 build 20527.20196", "LTSC 2024 17932.21140", "LTSC 2021 14334.21048", "Office 2019 10417.20236"], "affected": "Microsoft 365 Apps and Office builds before the 10 Nov 2026 update", "ecosystem": "vendor"}]
ecosystems: ["vendor"]
tags: ["macos", "microsoft-office", "package", "user-interaction", "windows", "word"]
not_affected_if: ["patched-nov-2026-build"]
published_at: "2026-11-10T19:18:19+00:00"
first_seen_at: "2026-11-10T19:24:26+00:00"
updated_at: "2026-11-11T00:41:04+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-109503", "first_seen_at": "2026-11-10T19:24:26+00:00"}, {"source": "analyst", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-109503", "first_seen_at": "2026-11-11T00:41:04+00:00", "cites": ["https://nvd.nist.gov/vuln/detail/CVE-2026-109503", "https://learn.microsoft.com/en-us/officeupdates/microsoft365-apps-security-updates", "https://www.cybersecurity-help.cz/vdb/vulns/164754/"]}]
exploit_sources: []
---

# Microsoft Word: double free lets an attacker run code over a network

Link for people: https://infrastack.ai/live/CVE-2026-109503 (this .md is for agents)

A double free in Microsoft Word (CWE-415) lets an attacker run code with the user's permissions. Microsoft's CVSS 8.8 vector has UI:R, so a user must open a crafted document. A third-party write-up says the trigger is exporting the document to PDF and that Preview Pane is not a vector; Microsoft's page was not read for this. Fixed in the November 10, 2026 Office updates. No exploitation or public PoC found.

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

## Affected

- vendor:Microsoft Office Word affected Microsoft 365 Apps and Office builds before the 10 Nov 2026 update fixed 2610 build 20527.20196, LTSC 2024 17932.21140, LTSC 2021 14334.21048, Office 2019 10417.20236

## How to check

In Word: File > Account > About Word. You are exposed if the build is lower than the fixed build for your channel: Current Channel 2610 build 20527.20196; Monthly Enterprise 2610 build 20527.20194, 2609 build 20430.20264, 2608 build 20326.20320; Office LTSC 2024 16.0.17932.21140; Office LTSC 2021 16.0.14334.21048; Office 2019 16.0.10417.20236. Mac: Office below 16.115.26110837 (per third-party sources, not confirmed on the Microsoft page I read).

## Fix

Install the November 10, 2026 Office update: Microsoft 365 Apps Current Channel 2610 build 20527.20196 or later; LTSC 2024 build 17932.21140; LTSC 2021 build 14334.21048; Office 2019 build 10417.20236. Mac: 16.115.26110837 (third-party sources).

## Timeline

- 2026-11-10T19:24:26+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-109503
- 2026-11-11T00:41:04+00:00 analyst https://nvd.nist.gov/vuln/detail/CVE-2026-109503 — Microsoft Learn Office release notes (Nov 10 2026) list CVE under Word and give fixed builds; MSRC page is JS-only, not read. PDF-export trigger comes only from Cybersecurity Help (third party). No exploitation or PoC found.

## Documents

- [advisory] NVD CVE-2026-109503 https://nvd.nist.gov/vuln/detail/CVE-2026-109503
- [fix] Microsoft Office security updates release notes (Nov 10, 2026) https://learn.microsoft.com/en-us/officeupdates/microsoft365-apps-security-updates
- [mentions] Double free in Microsoft Office - CVE-2026-109503 (Cybersecurity Help) https://www.cybersecurity-help.cz/vdb/vulns/164754/

## From the sources

Double free in Microsoft Office Word allows an unauthorized attacker to execute code over a network.

---

_Free to read, with fair use of about 60 pages a minute. For higher limits or API access: sales@infrastack.ai_