Outlook 365 / 2021 / 2019 / 2016 Update for February 2024

The February security and rollup update has been made available for all Click-to-Run installations of Outlook 2016, Outlook 2019, Outlook 2021 and Outlook as part of a Microsoft 365 subscription.

It contains 6 security updates for Outlook (2), Visio (1), Word (1), and Office (2). The details about the Outlook vulnerabilities can be found below;

  • CVE-2024-21378: Microsoft Outlook Remote Code Execution Vulnerability
    • This vulnerability is currently not publicly disclosed nor exploited.
    • Exploitation of the vulnerability requires that a user open a specially crafted file.
    • The Preview Pane is an attack vector.
    • The Exploitability Assessment is rated: Exploitation More Likely.
  • CVE-2024-21402: Microsoft Outlook Remote Code Execution Vulnerability
    • This vulnerability is currently not publicly disclosed nor exploited.
    • If the attacker successfully exploits the vulnerability, the attacker would gain the rights of the user that is running the affected application.
    • The Exploitability Assessment is rated: Exploitation Less Likely.

In addition, it contains 1 non-security fix related to Outlook Current Channel Version 2401, and 7 fixes related to Outlook Monthly Enterprise Version 2312.

  • 2401
    • We fixed an issue where the App Search bar was unexpectedly appearing above the message list in Outlook 2016 and Outlook 2019.
  • 2312
    • We fixed an issue that caused Outlook to exit unexpectedly when opening embedded mail attachments in another application.
    • We fixed an issue where the list of invalid recipients was showing duplicates.
    • We fixed an issue where Mail Tips were not showing for attachments.
    • We fixed an issue that caused Data Loss Prevention features to be unexpectedly disabled when disabling Optional Connected Experiences.
    • We fixed an issue where Skype for Business was shutting down unexpectedly at start up.
    • We fixed an issue where the message list was blank when switching between the “Focused” and “Other” views.
    • We fixed an issue that caused Outlook to exit unexpectedly after discarding an edit to a received single instance meeting.

Based on your release channel, you’ll be updated to the following version;

  • Microsoft 365 Apps, Outlook 2016 Retail, Outlook 2019 Retail, Outlook 2021 Retail
    Version 2401 (Build 17231.20236)
  • Monthly Enterprise
    Version 2312 (Build 17126.20190)
    Version 2311 (Build 17029.20178)
  • Semi-Annual Enterprise (Preview)
    Version 2308 (Build 16731.20550)
  • Semi-Annual Enterprise
    Version 2308 (Build 16731.20550)
    Version 2302 (Build 16130.20916)
    Version 2208 (Build 15601.20870) 
  • Outlook LTSC 2021
    Version 2108 (Build 14332.20637)
  • Outlook 2019 Volume Licensed
    Version 1808 (Build 10407.20032)

Note: Depending on your installation type, this update can be installed via the Update Now button in Outlook itself or the Microsoft Store. This update does not apply to msi-based installations of Office 2016.