Multiple Windows 10 Server versions are affected by a known issue introduced with the KB4503293, KB4503327, and KB4503286 cumulative updates, monthly rollups, and security-only updates released on June 11.

This new known issue Redmond acknowledged today may prevent computers from booting if they're using Preboot Execution Environment (PXE) images from System Center Configuration Manager (SCCM) or Windows Deployment Services (WDS) servers.

After the boot fail, the Windows devices affected by this issue will throw the following error: "Status: 0xc0000001, Info: A required device isn't connected or can't be accessed" after installing an affected update on a WDS server."

Affected Windows Server platforms

"Preboot execution environment (PXE)-initiated OS deployments in Configuration Manager let clients request and deploy operating systems over the network," explains Microsoft.

PXE-based OS deployments should be used for refreshing computers by deploying a new Windows version or for installing new Windows version on new devices.

Users who installed the following Windows updates may be impacted by this issue according to the list of known issues and notification published by Microsoft.

Support document Affected update KB4503293 LCU for Windows Server, version 1903. KB4503327 LCU for Windows Server, version 1809 and Windows Server 2019. KB4503286 LCU for Windows Server, version 1803. KB4503284 LCU for Windows 10, version 1709. KB4503267 LCU for Windows Server, version 1607 and Windows Server 2016. KB4503276 Monthly Rollup for Windows Server 2012 R2. KB4503285 Monthly Rollup for Windows Server 2012. KB4503292 Monthly Rollup for Windows Server 2008 R2 SP1. KB4503273 Monthly Rollup for Windows Server 2008 SP2 KB4503290 Security-only update for Windows Server 2012 R2. KB4503263 Security-only update for Windows Server 2012 and Windows Embedded 8 Standard. KB4503269 Security-only update for Windows Server 2008 R2 SP1 KB4503287 Security-only update for Windows Server 2008 SP2

Redmond also provides the full list of affected Windows platforms: Windows Server 2008 SP2; Windows Server 2008 R2 SP1; Windows Server 2012; Windows Server 2012 R2; Windows Server 2016; Windows Server, version 1803; Windows Server 2019; Windows Server, version 1809; Windows Server, version 1903.

Mitigation measures

Windows Server who want to mitigate this new known issue on an SCCM server will have to follow the following procedure:

Verify Variable Window Extension is enabled. Set the values of TFTP block size to 4096 and TFTP window size to 1. For guidance on how to configure them, see Customize the RamDisk TFTP block and window sizes on PXE-enabled distribution points.

For users that startup their systems via PXE using a WDS server without SCCM:

In WDS TFTP settings, verify Variable Window Extension is enabled. In the Boot Configuration Data (BCD) of the imported image, set RamDiskTFTPBlockSize to 1456. In the BCD of the imported image, set RamDiskTFTPWindowSize to 4.

Microsoft added that a solution for the issue blocking devices from starting using PXE from a WDS or SCCM servers is currently under development, to be released with an upcoming update.