May 14, 2019—KB4499158 (Security-only update)

Applies to: Windows Server 2012Windows Embedded 8 Standard

Improvements and fixes


This security update includes quality improvements. Key changes include:

  • Provides protections against a new subclass of speculative execution side-channel vulnerabilities, known as Microarchitectural Data Sampling, for 64-Bit (x64) versions of Windows (CVE-2019-11091, CVE-2018-12126, CVE-2018-12127, CVE-2018-12130). Use the registry settings as described in the Windows Server article. (These registry settings are disabled by default for Windows Server OS editions).
  • Security updates to Windows App Platform and Frameworks, Microsoft Graphics Component, Windows Storage and Filesystems, Windows Cryptography, Windows Datacenter Networking, Windows Wireless Networking, Windows Kernel, and the Microsoft JET Database Engine.

For more information about the resolved security vulnerabilities, please refer to the Security Update Guide.

Known issues in this update


Symptom Workaround
After installing this update, there may be issues using the Preboot Execution Environment (PXE) to start a device from a Windows Deployment Services (WDS) server configured to use Variable Window Extension. This may cause the connection to the WDS server to terminate prematurely while downloading the image. This issue does not affect clients or devices that are not using Variable Window Extension.

To mitigate the issue, disable the Variable Window Extension on WDS server using one of the following options:

Option 1:
Open an Administrator Command prompt and type the following:

Wdsutil /Set-TransportServer /EnableTftpVariableWindowExtension:No

Option 2:
Use the Windows Deployment Services UI.

  1. Open Windows Deployment Services from Windows Administrative Tools.
  2. Expand Servers and right-click a WDS server.
  3. Open its properties and clear the Enable Variable Window Extension box on the TFTP tab.

Option 3:
Set the following registry value to 0:

“HKLM\System\CurrentControlSet\Services\WDSServer\Providers\WDSTFTP\EnableVariableWindowExtension”.

Restart the WDSServer service after disabling the Variable Window Extension.

Microsoft is working on a resolution and will provide an update in an upcoming release.

Certain operations, such as rename, that you perform on files or folders that are on a Cluster Shared Volume (CSV) may fail with the error, “STATUS_BAD_IMPERSONATION_LEVEL (0xC00000A5)”. This occurs when you perform the operation on a CSV owner node from a process that doesn’t have administrator privilege.

Do one of the following:

  • Perform the operation from a process that has administrator privilege.
  • Perform the operation from a node that doesn’t have CSV ownership.
Microsoft is working on a resolution and will provide an update in an upcoming release.

How to get this update


This update is now available for installation through WSUS. To get the standalone package for this update, go to the Microsoft Update Catalog website.

File information

For a list of the files that are provided in this update, download the file information for update 4499158