CVE-2026-78525: Microsoft Office Outlook Remote Code Execution Vulnerability

Overview

Severity
High (CVSS 8.8)
CVSS Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C
Category
Remote Code Execution
Exploit Status
Not Exploited
Exploitation Likelihood
Less Likely
Patch Tuesday
2026-Sep
Released
2026-09-08

Description

Use after free in Microsoft Office Outlook allows an unauthorized attacker to execute code over a network.

FAQ

How could an attacker exploit the vulnerability? In an email attack scenario, an attacker could exploit the vulnerability by sending the specially crafted email to the victim. Exploitation of the vulnerability might involve either a victim opening a specially crafted email with an affected version of Microsoft Outlook software, or a victim's Outlook application displaying a preview of a specially crafted email . This could result in the attacker executing remote code on the victim's machine. Are the updates for the Microsoft Office LTSC for Mac currently available? The security update for Microsoft Office LTSC for Mac 2021 and 2024 are not immediately available. The updates will be released as soon as possible, and when they are available, customers will be notified via a revision to this CVE information. Is the Preview Pane an attack vector for this vulnerability? Yes, the Preview Pane is an attack vector.

Affected Products (13)

Microsoft Office

  • Microsoft Office 2019 for 32-bit editions
  • Microsoft Office 2019 for 64-bit editions
  • Microsoft 365 Apps for Enterprise for 32-bit Systems
  • Microsoft 365 Apps for Enterprise for 64-bit Systems
  • Microsoft Office LTSC for Mac 2021
  • Microsoft Office LTSC 2021 for 64-bit editions
  • Microsoft Office LTSC 2021 for 32-bit editions
  • Microsoft Office LTSC 2024 for 32-bit editions
  • Microsoft Office LTSC 2024 for 64-bit editions
  • Microsoft Office LTSC for Mac 2024
  • Microsoft Word 2016 (32-bit edition)
  • Microsoft Word 2016 (64-bit edition)
  • Microsoft Office 365 for Mac

Security Updates (1)

Acknowledgments

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Revision History

  • 2026-09-08: Information published.