May 12, 2026-KB5087052 Cumulative Update for .NET Framework 3.5 and 4.8.1 for Microsoft server operating system, version 23H2

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Note

  • Release Date:
    May 12, 2026
  • Version:
    .NET Framework 3.5 and 4.8.1

The May 12, 2026 update for Microsoft server operating system, version 23H2 includes security and cumulative reliability improvements in .NET Framework 3.5 and 4.8.1. We recommend that you apply this update as part of your regular maintenance routines. Before you install this update, see the Prerequisites and Restart requirement sections.

Summary

Security Improvements

CVE-2026-32177 - .NET Framework Elevation of Privilege vulnerability
              This security update addresses a Elevation of Privilege vulnerability detailed in CVE-2026-32177.

CVE-2026-35433 - .NET Framework Elevation of Privilege vulnerability
              This security update addresses a Elevation of Privilege vulnerability detailed in CVE-2026-35433.

Quality and Reliability Improvements

There are no new Quality and Reliability Improvements in this update.

Known issues in this update

Microsoft is not currently aware of any issues in this update.

How to get this update

Install this update

Release Channel Available Next Step
Windows Update and Microsoft Update Yes None. This update will be downloaded and installed automatically from Windows Update.
Windows Update for Business Yes None. This update will be downloaded and installed automatically from Windows Update.
Microsoft Update Catalog Yes To get the standalone package for this update, go to the Microsoft Update Catalog website.
Windows Server Update Services (WSUS) Yes This update will automatically sync with WSUS if you configure as follows:
Product: Microsoft server operating system, version 23H2
Classification: Security Updates

File information

For a list of the files that are provided in this update, download the file information for cumulative update.

Prerequisites

To apply this update, you must have .NET Framework 3.5 or 4.8.1 installed.

Restart requirement

You must restart the computer after you apply this update if any affected files are being used. We recommend that you exit all .NET Framework-based applications before you apply this update.

How to obtain help and support for this update