High CPU/High Memory in WSUS - Windows update will not download updates - stuck at 0% downloading

A WSUS update is now available that includes improvements for update metadata processing. This update should be applied to all WSUS servers in your environment.
Windows Server 2016 (KB4039396)
Windows Server 2012 R2 (KB4039871)
Windows Server 2012 (KB4039873)
WSUS 3.0 SP2 (KB4039929)

If you still occasionally experience thread abort exceptions, you can increase ASP.NET’s default timeout.
Increase the ASP.NET timeout

• Make a copy of \Program Files\Update Services\WebServices\ClientWebService\Web.Config.
• Open \Program Files\Update Services\WebServices\ClientWebService\Web.Config.
• Find the element “<httpRunTime”. It will look like this (in an unmodified web.config):

<httpRuntime maxRequestLength="4096" />

• Modify httpRunTime by adding an executionTimeout attribute:

<httpRuntime maxRequestLength="4096" executionTimeout="3600" />

• Save the web.config to a different location and copy the modified one into the directory.
• From an elevated command prompt, run IISReset to restart IIS