April 9, 2019—KB4493451 (Monthly Rollup)

Applies to: Windows Server 2012Windows Embedded 8 Standard

Improvements and fixes


This security update includes improvements and fixes that were a part of update KB4489920 (released March 19, 2019) and addresses the following issues:

  • Addresses an issue that causes the error "0x3B_c0000005_win32k!vSetPointer" when the kernel mode driver, win32k.sys, accesses an invalid memory location.
  • Addresses an issue that may cause applications that use MSXML6 to stop responding if an exception was thrown during node operations. 
  • Addresses an issue that causes the Group Policy editor to stop responding when editing a Group Policy Object (GPO) that contains Group Policy Preferences (GPP) for Internet Explorer 10 Internet settings. 
  • Addresses an issue that may cause authentication issues for Internet Explorer 10 and other applications that use WININET.DLL. This occurs when two or more people use the same user account for multiple, concurrent login sessions on the same Windows Server machine, including Remote Desktop Protocol (RDP) and Terminal Server logons.
  • Addresses an issue that may prevent Custom URI Schemes for Application Protocol handlers from starting the corresponding application for local intranet and trusted sites on Internet Explorer.
  • Addresses an issue that may cause compound document (OLE) server applications to display embedded objects incorrectly if you use the PatBlt API to place embedded objects into the Windows Metafile (WMF).

  • Security updates to Windows Storage and Filesystems, Windows Server, Microsoft Graphics Component, Windows Input and Composition, Windows Datacenter Networking, Windows Kernel, Windows MSXML, 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.

This issue is resolved KB4503285.

Microsoft and Sophos have identified an issue on devices with Sophos Endpoint Protection installed and managed by either Sophos Central or Sophos Enterprise Console (SEC) that may cause the system to become unresponsive upon restart after installing this update.

This issue has been resolved. Microsoft has removed the temporary block for all affected Windows updates.

Guidance for Sophos Endpoint and Sophos Enterprise Console customers can be found in the Sophos support article.

Microsoft and Avira have identified an issue on devices with Avira antivirus software installed that may cause the system to become unresponsive upon restart after installing this update.

This issue has been resolved. Microsoft has removed the temporary block for all affected Windows updates.

Avira has released an automatic update to address this issue. Guidance for Avira customers can be found in the Avira support article.
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 will be downloaded and installed automatically from Windows Update. 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 4493451