Download And Install KB4577671 Windows 10 Cumulative Update For October 2020 [Version 1909, 1903]

Windows UpdateWindows Update

Microsoft has released KB4577671 cumulative update for Windows 10 Version 1909 and Version 1903. This update is a part of the Microsoft Windows Patch Tuesday for October 2020 , which shall be automatically installed on all registered devices through Windows Update.

After installing the KB4577671 update, the build number of the operating system would become 18363.1139 for Version 1909, and 18362.1139 for Version 1903.

Let’s see what this update has to offer us. This will give us a good insight into why this update is important and when it is optimal for installation.

What’s new in KB4577671

As per Microsoft Security Response Center, a total of 48 vulnerabilities have been addressed for Windows 10 Version 1909 and for Windows 10 Version 1903 each. These do not include the 32-bit and ARM64 based systems.

7 of the vulnerabilities for version 1909 addressed are critical, all of which address remote code execution without authentication. Other significant matters addressed include elevation of privilege and denial of service. The exact same has been addressed for Windows 10 version 1903 as they both have the same core operating systems.

You may dig deeper into the details of the vulnerabilities addressed by Microsoft by downloading the respective excel sheet below.

Download And Install KB4577671 Windows 10 Cumulative Update For October 2020 [Version 1909, 1903] 3  Fixed Security Vulnerabilities in KB4577671 for Windows 10 Version 1909 (6.7 KiB, 975 hits)

Download And Install KB4577671 Windows 10 Cumulative Update For October 2020 [Version 1909, 1903] 3  Fixed Security Vulnerabilities in KB4577671 for Windows 10 Version 1909 (6.7 KiB, 845 hits)

The highlights of this update are:

Since Windows 10 Version 1909 and Version 1903 share the same core operating system and files, improvements in one automatically affect the other. Some of the improvements and fixes in KB4577671 are:

  • The issue with privilege elevation in win32k has been addressed.
  • When a Group Policy has been configured to delete cached profiles, an issue with the automatic deletion of critical files and folders from %systemroot%\system32 has been taken care of.
  • An issue with the null ports using the user interface has been fixed.
  • Several security patches have been updated such as for Windows App Platform and Frameworks, Windows Media, Windows Fundamentals, Windows Virtualization, Windows Authentication, Windows Kernel, Microsoft Graphics Component, etc.

For more elaborate information on KB4577671, checkout this Microsoft help page.

Install KB4577671 using Windows Update

The size of the update for both the versions 1909 and 1903 is 411MB. It should take around 10 minutes to download and install this update, including restarting the computer.

If you are missing any previous updates, installing KB4577671 will install all the security fixes included in all previous updates.

To install this update using Windows Update, please go to Windows Settings –> Update & Security –> Windows Update. In the right-hand pane, click on the Check for updates button.

You will then be able to see the update. Press Download and then Install to begin the installation.

Download KB4577671 Offline installers

These updates can also be installed on any computer having Windows 10 Version 1909 or Version 1903, without having an internet connection. Download the offline installers below as per your requirement :

For Windows 10 Version 1909

Download KB4577671 for Windows 10 Version 1909 64-bit [411.0 MB]

Download KB4577671 for Windows 10 Version 1909 32-bit [216.3 MB]

For Windows 10 Version 1903

Download KB4577671 for Windows 10 Version 1903 64-bit [411.0 MB]

Download KB4577671 for Windows 10 Version 1903 32-bit [216.3 MB]

To install the update, simply run the downloaded MSU file and Windows will automatically install the cumulative update.

You can check out your current Windows build by going to Run and then type winver.

To download any other updates related to KB4588671, please check Microsoft Catalog.

Known issues in KB4577671

One of the major issues Microsoft has highlighted associated with this update is when the Local System account is blocked by a firewall from accessing the internet via the HTTP protocol, and all the update packages are not downloaded. The user might then be prompted with a compatibility report dialog with “What needs your attention” at the top and the error, “Continuing with the installation of Windows will remove some optional features. You may need to add them back to Settings after the installation is complete.”

Microsoft is currently working on a solution to this problem. Meanwhile, users may need to ignore the prompt and move ahead with the update.

Another problem that some users might face after downloading this particular update is not being able to install third-party drivers. Users may be prompted with “Windows can’t verify the publisher of this driver software.” This is because Windows now requires a properly formatted and signed catalog file with the driver. If so, users will need to contact their device manufacturer and ask them to update their drivers accordingly.

Uninstall KB4577671 cumulative update

If you find that you cannot work with the new update installed, you can always uninstall it whenever you like. Here is a guide on how to uninstall a cumulative Windows update.

Cleanup after installing Windows Updates

If you want to save space after installing Windows updates, you can run the following commands:

dism.exe /Online /Cleanup-Image /AnalyzeComponentStore
dism.exe /Online /Cleanup-Image /StartComponentCleanup
Windows image cleanup KB4565351
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Subhan Zafar is an established IT professional with interests in Windows and Server infrastructure testing and research, and is currently working with Itechtics as a research consultant. He has studied Electrical Engineering and is also certified by Huawei (HCNA & HCNP Routing and Switching).


  • Bruce

    It refused to install on Windows 10 Home 64 1909 … Tried with the AV on and off, same thing. Tried it with the standalone installer, it failed. Let windows update try it 2 times and it failed. So obviously, Microsoft needs to check this update and release it under a newer number after it is really fixed. And I am not the only person who has had issues installing KB4577671

    • Usman Khurshid
      Usman Khurshid

      I’m having the same issue but with September’s patch Tuesday. Windows Update seems to download this update completely but then fails with an error message. Now I’m trying to download and install the latest update instead. Let’s see how it goes now.

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