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Updating Windows Update Agent

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Windows Update Agent (WUA) updates itself through various means, depending on the version of Windows running on the device. Old versions of WUA may not be able to connect to current update services, may not be compatible with all updates, and may not support all documented APIs. Here is how to insure that WUA is fully updated and compatible.

On versions of Windows beginning with Windows 7 and Windows Server 2008 R2

Windows Update Agent (WUA) updates are included in the regular periodic updates to Windows distributed through Windows Update or to Windows Server Update Services (WSUS). You do not need to take any special steps to update WUA on these Windows versions.

On versions of Windows prior to Windows 7 and Windows Server 2008 R2

WUA automatically updates itself when Automatic Updates connects to Windows Update or to WSUS.

If Automatic Updates has not yet successfully run, it is possible that a device running these Windows versions will be running an older version of WUA that does not support all the documented APIs. If you receive a WU_E_SELFUPDATE_REQUIRED result when you use the WUA API to perform a scan, download, or install, this error tells you that the installed version of WUA is too old to connect to current Windows Update services. You cannot use the normal WUA APIs to update WUA on these operating systems.

A user can manually update WUA to a current version by opening the Windows Update control panel, selecting Check for Updates, then accepting the self-update that appears. Alternately, you can update WUA programmatically.

To programmatically update WUA on versions of Windows prior to Windows 7 and Windows Server 2008 R2

  1. Use the WinHTTP APIs to download Wuredist.cab.
  2. Use the Cryptography Functions to verify that the downloaded copy of Wuredist.cab has a digital signature from Microsoft. If you can't verify the digital signature, stop.
  3. Use the File Decompression Interface APIs to extract the XML file from Wuredist.cab.
  4. Use the Microsoft XML Core Services (MSXML) APIs to load the XML file and locate the WURedist/StandaloneRedist/architecture node for the computer's architecture. For example, for x86, locate the WURedist/StandaloneRedist/architecture node with the name attribute of x86.
  5. Call IWindowsUpdateAgentInfo::GetInfo to determine the current version of WUA. If IWindowsUpdateAgentInfo::GetInfo returns a version number that is at least as high as the clientVersion attribute in the architecture node you located, stop.
  6. Use the MSXML APIs to read the downloadUrl attribute from the architecture node that you located. downloadUrl gives you the download URL for the appropriate WUA installer for the computer's architecture.
  7. Use the WinHTTP APIs to download the appropriate installer.
  8. Use the CreateProcess function or a similar API to execute the downloaded installer.