Microsoft Support:
August 26, 2025 - KB5064403 Cumulative Update for .NET Framework 3.5 and 4.8.1 for Windows 11, version 23H2
The August 26, 2025 update for Windows 11, 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 ImprovementsThere are no new security improvements in this release. This update is cumulative and contains all previously released security improvements.
Quality and Reliability Improvements
| ASP.NET | - Addressed an issue in ASP.NET where some error events fail to log properly in the Windows Event log. |
| WPF 1 | -Addressed an update for GB18030 certificate for Chinese language changes. |
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 | Go to Settings > Update & Security > Windows Update. In the Optional updates available area, you’ll find the link to download and install the update. |
| Windows Update for Business | Yes | Go to Settings > Update & Security > Windows Update. In the Optional updates available area, you’ll find the link to download and install the 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) | No | You can import this update into WSUS manually. See the Microsoft Update Catalog for instructions. |
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. Source:
