​Microsoft has fixed several bugs that cause install, upgrade, and Blue Screen of Death (BSOD) issues on Windows Server 2025 devices with a high core count.

The symptoms include Windows Server 2025 installation or upgrading processes failing or hanging, as well as server boot and restarts taking as much as three hours (or even more in some cases). Affected users may also experience blue screens when launching, restarting, or attempting to run apps.

However, as Redmond explains on the Windows release health dashboard, these issues are not triggered consistently on impacted devices.

To find if your Windows Server 2025 system is affected, use the CTRL+SHIFT+ESC keyboard shortcut to open the Windows Task Manager and check if the Performance tab shows over 256 logical processors.

“This issue was resolved by Windows updates released November 12, 2024 (KB5046617), and later,” the company said today. “We recommend you install the latest security update for your device as it contains important improvements and issue resolutions, including this one.”

Microsoft also provides a temporary workaround for those who can’t immediately install the KB5046617 November Patch Tuesday cumulative update, which requires admins to limit the number of logical processors on affected devices to less than 256.

To do that, you have to adjust how many logical processors are active by following these instructions:

1. Restart your server and enter the UEFI Setup. Navigate through the firmware menus, which may vary by manufacturer.
2. Locate any option which allows you to adjust the number of cores per socket.
3. Set the number of cores per socket to a value that ensures the total number of logical processors is 256 or fewer (Important: the total number of logical processors is calculated by first multiplying the number of sockets by the number of cores per socket and then multiplying that result by the number of logical processors per core.)
4. Restart the server.

“Changing the number of logical processors will vary depending on the firmware installed on your device,” the company added.

Microsoft is also investigating and working on fixing another Windows Server 2025 issue causing boot problems on systems in iSCSI environments and showing “boot device inaccessible” errors on affected devices.

Redmond announced last week that Windows Server 2025 is generally available, with a free 180-day trial available via the Microsoft Evaluation Center.

Windows Server 2025 is now Microsoft’s latest Long-Term Servicing Channel (LTSC) release for Windows Server.