Outlook broken on Windows 11? Microsoft releases urgent patch to fix cloud file bug

Microsoft has released an emergency out-of-band update for Windows 11 to fix a critical fault that caused Outlook to crash or become unusable for some users.

The patch addresses problems introduced by the January 2026 security update, which particularly affected applications that open or save files in cloud-backed locations such as OneDrive. Microsoft said the bug caused certain apps to stop responding or display error messages when interacting with cloud-synchronised files.

Outlook was among the most severely affected programs, especially on systems where Outlook data (.pst) files were stored in cloud-synced folders. Users reported repeated crashes, the application failing to open, or freezing indefinitely, effectively cutting off access to email.

Microsoft said the latest patch is cumulative, meaning it also includes earlier emergency fixes related to the January security release. Affected users are advised to install the update as soon as possible to restore normal Outlook functionality and prevent further instability when working with files stored in the cloud.

Second emergency fix this year

This is the second out-of-band update Microsoft has issued this year in response to issues stemming from the January 2026 Patch Tuesday release. Only last week, the company rolled out an emergency fix to resolve separate problems that prevented some Windows 11 devices from shutting down or entering hibernation, while other Windows 10 and Windows 11 systems were unable to log in via Remote Desktop.

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Out-of-band updates are typically reserved for serious flaws that cannot wait for Microsoft’s regular monthly update cycle. The need for two such releases in quick succession highlights the extent of the disruption caused by the January updates.