MSRC-CVE-2026-70291 — Microsoft Office Outlook Remote Code Execution Vulnerability

Summary

Impact: Remote Code Execution. Microsoft rating: Critical. Not known to be exploited — Exploitation Less Likely. Customer action: Required.

Details

Is the Preview Pane an attack vector for this vulnerability?
Yes, the Preview Pane is an attack vector.

Are the updates for Microsoft Office LTSC for Mac 2021 and 2024 currently available?
Yes. As of October 15, 2025, the security update for Microsoft Office LTSC for Mac 2021, 2024 and Microsoft Office 365 for Mac are available. Customers running Microsoft Office LTSC for Mac 2021, 2024 and Microsoft Office 365 for Mac should ensure the update is installed to be protected from this vulnerability.

How could an attacker exploit this vulnerability?
An attacker could send a specially crafted email message to a target user. Simply viewing the message in the Outlook Reading Pane could trigger the vulnerability, without the recipient opening the message or clicking anything in it. Successful exploitation could allow the attacker to execute code on the recipient's system. Network access is required; authentication and user interaction are not required.

Security updates
16.114.26101123 — https://learn.microsoft.com/en-us/officeupdates/release-notes-office-for-mac
16.0.14334.20974 — https://docs.microsoft.com/en-us/officeupdates/microsoft365-apps-security-updates
https — https://learn.microsoft.com/en-us/officeupdates/microsoft365-apps-security-updates

Vulnerabilities 1

Critical 9.8

CVE-2026-70291

Microsoft Office Outlook Remote Code Execution Vulnerability

Heap-based buffer overflow in Microsoft Office Outlook allows an unauthorized attacker to execute code over a network.

Microsoft Microsoft 365 Apps for Enterprise Microsoft Office LTSC 2021 Microsoft Office LTSC 2024

Oct 13, 2026

Revision history

2026-11-10 #3
Updated an acknowledgement. This is an informational change only.
2026-10-15 #2
Microsoft is announcing the availability of the security updates for Microsoft Office for Mac. Customers running affected Mac software should install the update for their product to be protected from this vulnerability. Customers running other Microsoft Office software do not need to take any action. See the [Release Notes](https://go.microsoft.com/fwlink/p/?linkid=831049) for more information and download links.
2026-10-13 #1
Information published.

References

CVE-2026-70291 Microsoft Office Outlook Remote Code Execution Vulnerability - HTML
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-70291
Microsoft Exploitability Index
https://www.microsoft.com/en-us/msrc/exploitability-index?rtc=1
Microsoft Support Lifecycle
https://support.microsoft.com/lifecycle
Common Vulnerability Scoring System
https://www.first.org/cvss