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Patch Management / Patch Tuesday / Windows 10

High CPU Usage for the WSUS Server After August Cumulative Update

We’ve covered the issue where Microsoft introduced a bug in the Windows 10 1607 CU for August that causes update history to disappear after installation. But, there’s one additional bug that Microsoft is also still investigating and attempting to develop a fix. And, as the days of August roll on and customers continue testing, this one seems to be causing the most trouble.

Microsoft originally stated that…

WSUS servers will exhibit increased CPU, memory, and network utilization when Windows Update clients perform their first scan after installing KB4034658.

But, the issue has grown a bit, including the following symptoms…

  • High CPU on your WSUS server – 70-100% CPU in w3wp.exe hosting WsusPool
  • High memory in the w3wp.exe process hosting the WsusPool – customers have reported memory usage approach 24GB
  • Constant recycling of the W3wp.exe hosting the WsusPool (identifiable by the PID changing)
  • Clients failing to scan with 8024401c (timeout) errors in the WindowsUpdate.log
  • Mostly 500 errors for the /ClientWebService/Client.asmx requests in the IIS logs


Microsoft says that the issue revolves around the large amount of update metadata that Windows 10 1607 has accumulated over time and that eventually this will affect more recent versions of Windows 10, too. Microsoft is offering guidance for maintenance on the IIS portion of the WSUS server to temporarily resolve issues until it can provide an ultimate resolution:

High CPU/High Memory in WSUS following Update Tuesdays


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