---
id: "CVE-2026-118294"
page: "https://infrastack.ai/live/CVE-2026-118294"
kind: "vulnerability"
aliases: ["CVE-2026-118294"]
title: "Microsoft Excel: heap overflow lets a remote attacker run code"
severity: "high"
cvss: 8.8
epss: null
exploited: false
status: "open"
category: "other"
products: [{"name": "Microsoft Excel (Microsoft 365 Apps, Office LTSC 2021/2024)", "fixed": ["16.0.14334.21048", "16.0.17932.21140", "16.115.26110837"], "affected": "LTSC 2021 < 16.0.14334.21048; LTSC 2024 < 16.0.17932.21140; Mac < 16.115.26110837; 365 Apps before Nov 10 2026 builds", "ecosystem": "vendor"}]
ecosystems: []
tags: ["excel", "macos", "microsoft-office", "other", "user-interaction", "windows"]
not_affected_if: ["patched-nov-2026-build"]
published_at: "2026-11-10T19:19:42+00:00"
first_seen_at: "2026-11-10T19:24:51+00:00"
updated_at: "2026-11-10T23:14:15+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-118294", "first_seen_at": "2026-11-10T19:24:51+00:00"}, {"source": "analyst", "url": "https://app.opencve.io/cve/CVE-2026-118294", "first_seen_at": "2026-11-10T23:14:15+00:00", "cites": ["https://app.opencve.io/cve/CVE-2026-118294", "https://learn.microsoft.com/en-us/officeupdates/microsoft365-apps-security-updates"]}]
exploit_sources: []
---

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

Link for people: https://infrastack.ai/live/CVE-2026-118294 (this .md is for agents)

Heap-based buffer overflow (CWE-122) in Microsoft Office Excel allows an unauthorized attacker to execute code over a network. Microsoft's CNA record scores it CVSS 8.8 with user interaction required (opening a crafted file); exploitation status marked unproven (E:U). Fixed in the November 10, 2026 Office updates.

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

## Affected

- vendor:Microsoft Excel (Microsoft 365 Apps, Office LTSC 2021/2024) affected LTSC 2021 < 16.0.14334.21048; LTSC 2024 < 16.0.17932.21140; Mac < 16.115.26110837; 365 Apps before Nov 10 2026 builds fixed 16.0.14334.21048, 16.0.17932.21140, 16.115.26110837

## How to check

In Excel: File > Account > About Excel, compare the build with the fixed builds (Windows: LTSC 2024 >= 16.0.17932.21140, LTSC 2021 >= 16.0.14334.21048, Current Channel >= 2610 build 20527.20196; Mac: >= 16.115.26110837). Fleet: query Office build via inventory. Also check Office Online Server (CNA lists < 16.0.10417.20236).

## Fix

Install the November 10, 2026 Office security update. Fixed builds: Current Channel 2610 (20527.20196); Monthly Enterprise 2610 (20527.20194), 2609 (20430.20264), 2608 (20326.20320); Office LTSC 2024 16.0.17932.21140; Office LTSC 2021 16.0.14334.21048; Office for Mac 16.115.26110837. Click-to-Run updates through Office update.

## Timeline

- 2026-11-10T19:24:51+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-118294
- 2026-11-10T23:14:15+00:00 analyst https://app.opencve.io/cve/CVE-2026-118294 — MSRC update-guide page is JS-only and empty; Learn release notes (vendor) list CVE under Excel for Nov 10 2026 builds; affected ranges/UI:R come from OpenCVE mirror of Microsoft CNA record, not verified. No exploitation reported; no social search done (no named issue). Office Online Server row in CNA data seems inconsistent (Office 2019-style build).

## Documents

- [describes] OpenCVE: CVE-2026-118294 (mirror of Microsoft CNA record) https://app.opencve.io/cve/CVE-2026-118294
- [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.

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