KB5003173 for Windows 10 21H1, 20H2, 2004 May 2021 Patch Tuesday update

New LCU KB5003173 for Windows 10 2004, 20H2, 21H1 May 2021 Patch Tuesday Windows update changes, fixes, direct download links, and the ways to install.


Series of Security patches are started arriving at different Window versions. KB5003173 is the latest one that is for Windows 10 21H1, 20H2, and 2004. The update carries significant changes and bug fixes and some known issues.

KB5003173 is automatically as well as manually downloadable and installable.

KB5003173 Windows 10 21H1 20H2, 2004 May 2021 Patch Tuesday Windows update

Here is the Changelog –

Changes and bug fixes

The rollout incorporates Security patches to Windows App Platform and Frameworks, Windows Kernel, Windows Media, Microsoft Scripting Engine, and Windows Silicon Platform.

Known issues in this patch



User and system certificates might be missing when updating from Windows 10 v1809 or later to a greater edition. You will only be impacted if you have obtained CU Sep 16, 2020, or later and then advance to update to a greater version. The issue occurs when using media or an installation source that does not have a CU rolled out Oct 13, 2020, or later integrated. The problem essentially occurs when managed devices are updated using outdated bundles or media via WSUS or Microsoft Endpoint Configuration Manager. Furthermore, this might take place when using obsolete physical media or ISO images that do not have the latest updates integrated.

Remark – If you are using Windows Update for Business or that connect straight to Windows Update are not impacted.

If you have already confronted this issue mitigate it within the uninstall window by going back to your previous version using the guidelines here. See – How to change the roll back period to 60 days in Windows 10.

Redmondians are working on a resolution and will provide updated bundles and refreshed media in the coming weeks.

When using the Microsoft Japanese IME to type Kanji characters in an application that automatically allows the input of Furigana characters, you might not get the faultless Furigana characters. You might need to type in the Furigana characters manually.

Remark РThe influenced apps are using the ImmGetCompositionString() function.

The tech giant is working on a resolution and will provide an update in a forthcoming release.

How to download KB5003173 and install

Make sure to install SSU KB prior to starting the installation of the May 2021 security patch. Now, follow the instructions –

Via Windows update

  1. Press the Winkey, type updates, and hit enter.
  2. Click – Check for updates.
  3. Let the system complete scanning and downloading the patch.
  4. At last, click – Install now.

Through Microsoft update catalog

  1. Click KB5003173 direct download link here.
  2. Find the file suitable for your system architecture and Windows version and select – Download.
  3. A separate page will prompt; click the solitary link here.
  4. After the downloading is finished, double click the .MSU file and pursue the installation.

That’s all!!

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Topics:  Windows update
About Sunita
Love to play with Windows 11 and 10. Suggestion - Going for Registry change or system files edit then remember to take a backup or create a restore point before Starting.