KB5091573: [Domain controllers (known issue)] Fixed

April 19, 2026—KB5091573 (OS Build 17763.8647) Out-of-band

This out-of-band update includes fixes and improvements that are part of the following update:

• April 14, 2026—KB5082123 (OS Build 17763.8644)

The following is a summary of the issues that this out-of-band update addresses when you install this update. The bold text within the brackets indicates the item or area of the change we are documenting.

- [Domain controllers (known issue)] Fixed: After installing the April 14, 2026, (KB5082123) 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.

If you installed earlier updates, only the new updates contained in this package will be downloaded and installed on your device.