Download and install September 8, 2026—KB5122876 (OS Build 17763.9245)

Hi anab,

To manually install a specific patch on Windows Server 2019, you must download the offline standalone package from the official Microsoft Update Catalog. Once you download the file, which ends in the .msu extension, you can deploy it using the Windows Update Standalone Installer. You do this by opening Command Prompt and running the executable located at C:\Windows\System32\wusa.exe followed by a space and the path to your downloaded file. This native utility safely unpacks the update binaries and integrates them directly into your server's operating system.

However, I strongly advise against installing KB5122876. Microsoft has confirmed that this specific September 2026 update contains a severe bug that causes Remote Desktop Services to freeze. Deploying it will block new administrative connections and prevent current users from properly logging off.

Because Windows Server utilizes cumulative updates, you can safely bypass that broken patch without missing its critical security payload. Instead, search the Microsoft Update Catalog for KB5129238. This is an official out-of-band update released shortly after that advances your OS build while entirely resolving the Remote Desktop Services deadlock. Deploying this newer package using the wusa.exe tool will ensure your server remains fully patched, secure, and accessible.

Hope this answer has brought you some useful information. If it did, please hit “accept answer”. Should you have any questions, feel free to leave a comment.

VPHAN