2026's first Patch Tuesday broke shutdowns, logins and Outlook at once
January 2026 update caused black screens, boot failures and Outlook crashes
The market's verdict: -4.8% on MSFT in the week after.
What actually happened
The first Patch Tuesday of 2026, KB5074109, arrived January 13 and immediately went multi-threat: black screens before the desktop appeared, machines that would not shut down or sleep, Outlook Classic freezing and crashing, File Explorer ignoring folder customizations, and broken authentication in remote connection tools. Microsoft confirmed at least three of the issues and shipped an emergency out-of-band fix on January 17. A strong opening statement of intent for the year, and the year took note.
This one is officially acknowledged.
Were you affected? Unbreak it
Uninstall the January update ↗
wusa /uninstall /kb:5074109 /quiet /norestart
Emergency out-of-band fix shipped January 17 ↗
Microsoft has acknowledged this issue; a fix ships in an out-of-band or next cumulative update. Check Windows Release Health before manual workarounds.
Links
↳ caused by KB5074109
Timeline
- Jan 13, 2026 Confirmed First reports came in.
- Jan 17, 2026 Fixed Emergency out-of-band update shipped.