---
id: "CVE-2026-120791"
page: "https://infrastack.ai/live/CVE-2026-120791"
kind: "vulnerability"
aliases: ["CVE-2026-120791"]
title: "Microsoft Excel: heap overflow lets an attacker run code over network"
severity: "high"
cvss: 8.8
epss: null
exploited: false
status: "open"
category: "other"
products: [{"name": "Microsoft Office Excel", "fixed": [], "affected": "", "ecosystem": "vendor"}]
ecosystems: ["vendor"]
tags: ["excel", "microsoft-office", "other", "windows"]
not_affected_if: []
published_at: "2026-11-10T19:20:28+00:00"
first_seen_at: "2026-11-10T19:25:08+00:00"
updated_at: "2026-11-10T21:47:59+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-120791", "first_seen_at": "2026-11-10T19:25:08+00:00"}, {"source": "analyst", "url": null, "first_seen_at": "2026-11-10T21:47:59+00:00"}]
exploit_sources: []
---

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

Link for people: https://infrastack.ai/live/CVE-2026-120791 (this .md is for agents)

A heap-based buffer overflow in Microsoft Office Excel can let an attacker run code on a machine. Microsoft's CVSS vector (8.8) lists the attack as network-delivered with user interaction required, which usually means a victim must open a crafted file. Affected Excel builds and patched versions are not yet confirmed from Microsoft's own advisory.

_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

## How to check

Open the Microsoft Security Update Guide entry for CVE-2026-120791, find your Office edition (Microsoft 365 Apps, Office LTSC, 2021 etc.) and compare the build in Excel > File > Account > About Excel against the fixed build. Affected and fixed builds were not confirmed by the analyst.

## Timeline

- 2026-11-10T19:25:08+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-120791
- 2026-11-10T21:47:59+00:00 analyst — Could not read the MSRC Security Update Guide entry (JS-only page returned a loading stub; browser-cli 402 out of minutes). No affected builds, fixed builds or fix state confirmed; nothing verified. Only the CNA vector (secure@microsoft.com) is known: AV:N/AC:L/PR:N/UI:R, so user interaction is required (likely opening a crafted file). No exploitation or PoC found in the sources; X/social not searched. Revisit when the MSRC page or a CVRF/KB is readable.

## 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_