---
id: "CVE-2026-118299"
page: "https://infrastack.ai/live/CVE-2026-118299"
kind: "vulnerability"
aliases: ["CVE-2026-118299"]
title: "Microsoft Excel: heap overflow lets an attacker run code over a network"
severity: "high"
cvss: 8.8
epss: null
exploited: false
status: "open"
category: "other"
products: [{"name": "Microsoft Office LTSC 2024", "fixed": ["16.0.17932.21140"], "affected": "< 16.0.17932.21140", "ecosystem": "vendor"}, {"name": "Microsoft Office LTSC 2021", "fixed": ["16.0.14334.21048"], "affected": ">= 16.0.1, < 16.0.14334.21048", "ecosystem": "vendor"}, {"name": "Microsoft Office LTSC for Mac 2024/2021 and Office 365 for Mac", "fixed": ["16.115.26110837"], "affected": "< 16.115.26110837", "ecosystem": "vendor"}, {"name": "Office Online Server", "fixed": ["16.0.10417.20236"], "affected": "< 16.0.10417.20236", "ecosystem": "vendor"}, {"name": "Microsoft 365 Apps for Enterprise", "fixed": [], "affected": ">= 16.0.1, fixed per aka.ms/OfficeSecurityReleases", "ecosystem": "vendor"}]
ecosystems: []
tags: ["excel", "macos", "microsoft-office", "other", "user-interaction", "windows"]
not_affected_if: ["patched-build"]
published_at: "2026-11-10T19:19:43+00:00"
first_seen_at: "2026-11-10T19:24:52+00:00"
updated_at: "2026-11-10T23:12:54+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-118299", "first_seen_at": "2026-11-10T19:24:52+00:00"}, {"source": "analyst", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-118299", "first_seen_at": "2026-11-10T23:12:54+00:00", "cites": ["https://nvd.nist.gov/vuln/detail/CVE-2026-118299", "https://learn.microsoft.com/en-us/officeupdates/microsoft365-apps-security-updates"]}]
exploit_sources: []
---

# Microsoft Excel: heap overflow lets an attacker run code over a network

Link for people: https://infrastack.ai/live/CVE-2026-118299 (this .md is for agents)

Heap-based buffer overflow in Microsoft Office Excel (CWE-122). Microsoft rates it 8.8 (CVSS AV:N/PR:N/UI:R): an attacker needs a victim to open a crafted spreadsheet. Fixed in the 10 Nov 2026 Office updates. No exploitation reported; not on CISA KEV.

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

## Affected

- vendor:Microsoft Office LTSC 2024 affected < 16.0.17932.21140 fixed 16.0.17932.21140
- vendor:Microsoft Office LTSC 2021 affected >= 16.0.1, < 16.0.14334.21048 fixed 16.0.14334.21048
- vendor:Microsoft Office LTSC for Mac 2024/2021 and Office 365 for Mac affected < 16.115.26110837 fixed 16.115.26110837
- vendor:Office Online Server affected < 16.0.10417.20236 fixed 16.0.10417.20236
- vendor:Microsoft 365 Apps for Enterprise affected >= 16.0.1, fixed per aka.ms/OfficeSecurityReleases fixed no fixed version listed

## How to check

Open Excel > File > Account and compare the build with the fixed builds: Office LTSC 2024 16.0.17932.21140, Office LTSC 2021 16.0.14334.21048, Office for Mac 16.115.26110837, Office Online Server 16.0.10417.20236. Microsoft 365 Apps: Current Channel 2610 build 20527.20196 or later (see https://aka.ms/OfficeSecurityReleases).

## Fix

Install the 10 Nov 2026 Office security update: LTSC 2024 16.0.17932.21140, LTSC 2021 16.0.14334.21048, Office for Mac 16.115.26110837, Office Online Server 16.0.10417.20236, Microsoft 365 Apps per aka.ms/OfficeSecurityReleases.

## Timeline

- 2026-11-10T19:24:52+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-118299
- 2026-11-10T23:12:54+00:00 analyst https://nvd.nist.gov/vuln/detail/CVE-2026-118299 — MSRC page unreadable by tools; used Microsoft CNA data via NVD/OpenCVE and Office release notes (Nov 10 2026). Not marked verified. No exploitation reported, not in KEV. CVE-2026-118299 listing under Excel in the Learn notes not confirmed.

## Documents

- [describes] NVD CVE-2026-118299 (Microsoft CNA data) https://nvd.nist.gov/vuln/detail/CVE-2026-118299
- [fix] Microsoft Office security updates release notes (Nov 10, 2026) https://learn.microsoft.com/en-us/officeupdates/microsoft365-apps-security-updates

## From the sources

Heap-based buffer overflow in Microsoft Office Excel 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_