---
id: "CVE-2026-123376"
page: "https://infrastack.ai/live/CVE-2026-123376"
kind: "vulnerability"
aliases: ["CVE-2026-123376"]
title: "Microsoft Outlook: heap buffer overflow lets an attacker run code remotely"
severity: "high"
cvss: 8.8
epss: null
exploited: false
status: "open"
category: "other"
products: [{"name": "Microsoft Office Outlook", "fixed": [], "affected": "", "ecosystem": "vendor"}]
ecosystems: ["vendor"]
tags: ["microsoft-office", "other", "outlook", "windows"]
not_affected_if: []
published_at: "2026-11-10T19:20:40+00:00"
first_seen_at: "2026-11-10T19:25:12+00:00"
updated_at: "2026-11-10T21:34:21+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-123376", "first_seen_at": "2026-11-10T19:25:12+00:00"}, {"source": "analyst", "url": null, "first_seen_at": "2026-11-10T21:34:21+00:00"}]
exploit_sources: []
---

# Microsoft Outlook: heap buffer overflow lets an attacker run code remotely

Link for people: https://infrastack.ai/live/CVE-2026-123376 (this .md is for agents)

A heap-based buffer overflow in Microsoft Office Outlook can be triggered over a network by an unauthorized attacker. A successful attack lets the attacker execute code on the affected machine.

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

## Affected

- vendor:Microsoft Office Outlook affected range not listed fixed no fixed version listed

## Timeline

- 2026-11-10T19:25:12+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-123376
- 2026-11-10T21:34:21+00:00 analyst — MSRC page is JavaScript-only and returned no text through web-cli or WebFetch; NVD page came back empty. No primary document linked, nothing verified. Only the user-interaction requirement is known, from the CVSS vector from secure@microsoft.com. Not the exploited zero-day: the November Patch Tuesday Outlook zero-day is CVE-2026-124194 (NTLM spoofing), a different CVE. A revisit should read MSRC through browser-cli for affected builds and the fixed Click-to-Run/MSI versions. Several sibling Outlook RCEs were published at the same time (CVE-2026-123375, -123377, -123380 to -123383). X was not checked.

## From the sources

Heap-based buffer overflow in Microsoft Office Outlook 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_