Download and Install KB4576945 .NET Framework Windows 10 2004

Microsoft releases Oct 2020 .NET Framework patch for Windows 10 2004 under the name “KB4576945”. This cumulative update brings quality and reliability improvements for Windows Communication Foundation, Common Language Runtime, ASP.NET, and Winforms. Besides, it came for Windows 10 version 20H1 as well as Windows Server, version 2004. 


KB4576945 .NET Framework 4.8, 3.5 Changelog

Here are the key changes for WCR, Winforms, ASP.NET, AQL, and CLR –

Windows Communication Runtime 

  • Earlier, when users start multiple services simultaneously, WCF simply fails to launch. Microsoft team has addressed this issue on KB4576945.


  • The company resolves a regression which was previously introduced in .NET Framework 4.8. 
  • From now onward, .NET Framework 4.8 will use the type name instead of the DisplayMember property value to access names. 


  • Microsoft disabled the reuse of AppPathModifier in ASP.Net control output.
  • The new HttpCookie objects in the ASP.Net will use the default cookie flags as opposed to earlier practices of using .NET-style primitive defaults. 

Common Language Runtime

  • The tech giant introduces a CLR config variable Thread_AssignCpuGroups (1 by default). One can set this to value “0” so as to disable the automatic CPU group assignment done by the CLR for new threads. Thread pool and Thread.Start() are two such threads that can create new threads and allow apps to do its own thread-spreading.
  • Furthermore, they resolve an issue regarding timers with very long due times ticking down much sooner than expected. This is effective only when the AppContext switch “Switch.System.Threading.UseNetCoreTimer” stays enabled. 
  • Microsoft resolves a rare data corruption issue that can occur while using a new API such as Unsafe.


  • There won’t occur issues when you connect to an Azure SQL database, perform an enclave-based operation; and then attempt connecting to some other database under the same server having a similar Attestation URL.

Download and Install KB4576945 .NET Framework

Windows 10 users usually get notification regarding new cumulative updates or .NET Framework via Windows Update. In case you don’t see any prompt for the KB4576945 patch, you may try any of the following two ways –

1] Microsoft Update Catalog

This is the easiest of the two methods discussed here. All you require is to visit the update catalog webpage and click the Download button next to the update that matches your system architecture. 

2] Through Windows Update

  • Reach out to the below patch and click “Check for updates”.

Settings > Update & Security > Windows Update

  • The system will then look for any pending updates online. And if available, this will automatically download and install the same.
  • When the installation finishes, there appears a prompt asking to Reboot the device.


  1. After I loaded this update — KB4576478 — my HP laptop is running so slow. On the Task Manager, Performance tab, the disk is running 100% for 15-20 minutes, and websites that used to open quickly take 2 minutes or more to open. I uninstalled this update, and my computer reverted back to normal speed. But the update crept in again on its own over night (even after I paused all Windows updates because of this issue). Defrag is 1% fragmented and Optimize Disk showed no problems. I also ran a full scan and malware scan on Windows Defender. Any advice would be appreciated (I am a basic user, and hesitate messing with Registry)

  2. Update KB4576945 rendered my external speakers useless unless I plug them into the headphone outlet. Once I uninstalled this update, my external speakers work again.
    I have a brand new Dell XPS Windows 10 with Dell external speakers.

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