---
id: "CVE-2026-118718"
page: "https://infrastack.ai/live/CVE-2026-118718"
kind: "vulnerability"
aliases: ["CVE-2026-118718"]
title: "Microsoft Excel: heap buffer overflow lets a remote attacker run code"
severity: "high"
cvss: 8.8
epss: null
exploited: false
status: "open"
category: "other"
products: [{"name": "Microsoft Office Excel", "fixed": [], "affected": "", "ecosystem": "vendor"}, {"name": "Microsoft 365 Apps for Enterprise", "fixed": ["Current Channel 2610 build 20527.20196"], "affected": ">= 16.0.1, below the Nov 10 2026 build for your channel", "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 2024", "fixed": ["16.0.17932.21140"], "affected": ">= 16.0.0, < 16.0.17932.21140", "ecosystem": "vendor"}, {"name": "Microsoft Office for Mac (365, LTSC 2021, LTSC 2024)", "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"}]
ecosystems: ["vendor"]
tags: ["excel", "macos", "microsoft-office", "other", "user-interaction", "windows"]
not_affected_if: ["patched-nov-2026"]
published_at: "2026-11-10T19:19:47+00:00"
first_seen_at: "2026-11-10T19:24:54+00:00"
updated_at: "2026-11-10T23:04:05+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-118718", "first_seen_at": "2026-11-10T19:24:54+00:00"}, {"source": "analyst", "url": "https://app.opencve.io/cve/CVE-2026-118718", "first_seen_at": "2026-11-10T23:04:05+00:00", "cites": ["https://app.opencve.io/cve/CVE-2026-118718", "https://learn.microsoft.com/en-us/officeupdates/microsoft365-apps-security-updates"]}]
exploit_sources: []
---

# Microsoft Excel: heap buffer overflow lets a remote attacker run code

Link for people: https://infrastack.ai/live/CVE-2026-118718 (this .md is for agents)

A heap-based buffer overflow in Microsoft Office Excel lets an unauthorized attacker run code over a network. The sources give no further detail on how the file or request is delivered.

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

## Affected

- vendor:Microsoft Office Excel affected range not listed fixed no fixed version listed
- vendor:Microsoft 365 Apps for Enterprise affected >= 16.0.1, below the Nov 10 2026 build for your channel fixed Current Channel 2610 build 20527.20196
- vendor:Microsoft Office LTSC 2021 affected >= 16.0.1, < 16.0.14334.21048 fixed 16.0.14334.21048
- vendor:Microsoft Office LTSC 2024 affected >= 16.0.0, < 16.0.17932.21140 fixed 16.0.17932.21140
- vendor:Microsoft Office for Mac (365, LTSC 2021, LTSC 2024) affected < 16.115.26110837 fixed 16.115.26110837
- vendor:Office Online Server affected < 16.0.10417.20236 fixed 16.0.10417.20236

## How to check

In Excel open File > Account > About Excel and compare the build to the fixed builds in the fix field (Windows: 16.0.<build>; Mac: Excel > About Excel). Managed fleets: query installed Office build/channel and flag anything older than the November 10, 2026 build for its channel.

## Fix

Install the November 10, 2026 Office update. Microsoft 365 Apps: Current Channel 2610 build 20527.20196 (Monthly Enterprise 2610 20527.20194, 2609 20430.20264, 2608 20326.20320; Semi-Annual 2610 20527.20192, 2609 20430.20262, 2608 20326.20318). Office LTSC 2024 Volume: 16.0.17932.21140. Office LTSC 2021 Volume: 16.0.14334.21048. Office for Mac / LTSC for Mac 2021 and 2024: 16.115.26110837. Office Online Server: 16.0.10417.20236.

## Timeline

- 2026-11-10T19:24:54+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-118718
- 2026-11-10T23:04:05+00:00 analyst https://app.opencve.io/cve/CVE-2026-118718 — Microsoft Nov 10 2026 Patch Tuesday Excel RCE; release-notes page (Microsoft Learn) lists the CVE in the Nov 10 builds. Affected ranges are from the CNA record via OpenCVE (MSRC page is JS-only, not read directly), so not verified. No exploitation reported (CNA E:U). User interaction required per vector.

## Documents

- [describes] OpenCVE: CVE-2026-118718 (Microsoft CNA record) https://app.opencve.io/cve/CVE-2026-118718
- [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_