On 11 May 2021, Microsoft announced the release of the May 2021 cumulative Update for .NET Framework 3.5 and 4.8 (KB4601554). This update was supposed to be made available through Windows Update, WSUS, and Microsoft Update Catalog for Windows 10 version 20H2.
Unfortunately, this update is faulty.
Windows Update on Windows 10 version 20H2 does not find or install any such update. I tried downloading the package directly from the Microsoft Update Catalog, but it refused to install, generating the following error message:
Windows Update Standalone Installer:
Update for Windows (KB4601554) is already installed on this computer.
I inspected the package’s digital signature and discovered that the package had been sealed with a digital signature on 11 February 2021, one day after the release of the previous cumulative update (KB4601050). It had not been altered ever since. As such, these packages could not possibly contain a patch for the issues that Microsoft claims to have discovered between February and May. Whatever this package contains, my computer doesn’t need it.
According to Microsoft Tara Overfield, as part of the May 2021 rollup, Microsoft has released .NET Framework updates for other versions of Windows as well. I decided to inspect one at random. I picked the updates for Windows 10 version 1809: 4601558 and 4601555. Both were faulty; they were digitally signed on 11 February 2021.
Overall, it seems Microsoft has pushed a collection of placeholder packages into the update channel. Computers running Windows 10, Windows Server 2016, and Windows Server 2019 are affected.
I also inspected the two .NET Framework 4.x updates for Windows 8.1 (KB5001845 and KB5001850). These packages were signed on 1 April 2021, not May.
Confidential Files! 