April 19, 2026—Hotpatch KB5091470 (OS Build 26100.32704) Out-of-band

This out-of-band (OOB) update for Windows Server 2025 (KB5091470) is a non-security cumulative update.

To view the latest updates about this release, visit the Windows release health dashboard or the update history page for Windows Server 2025.

Note: Windows Server 2025 Datacenter & Standard machines connected to Azure Arc, now have the option to subscribe to Hotpatch servicing. Hotpatch provides the ability to install OS security updates without restarting your machine.

Improvements and fixes

The following summary outlines key issues addressed by this out-of-band update. The bold text within the brackets indicates the item or area of the change.

[Domain controllers (known issue)] Fixed: After installing the April 14, 2026, (KB5082063) Windows security update and restarting, domain controllers with multi-domain forests that use Privileged Access Management (PAM), might experience startup issues. In some cases, Local Security Authority Subsystem Service (LSASS) might stop responding, leading to repeated restarts, and preventing authentication and directory services, which can make the domain unavailable.Note: The update is only offered to devices that already installed KB5082063.

Note: This Hotpatch update will install and take effect without requiring you to restart the device. For more information see Hotpatch updates.

If you've already installed previous updates, your device will download and install only the new updates included in this package.

Known issues in this update

After installing KB5070893 or later updates, Windows Server Update Services (WSUS) does not display synchronization error details within its error reporting. This functionality is temporarily removed to address the Remote Code Execution Vulnerability, CVE-2025-59287.

How to get this update

Before you install this update

Microsoft now combines the latest servicing stack update (SSU) for your operating system with the Hotpatch update. For general information about SSUs, see Servicing stack updates.

If you are using Windows Update, the latest SSU installs with this update.

Install this update

To install this update, use one of the following Windows and Microsoft release channels.