Note
- Release Date:
September 9, 2025 - Version:
.NET Framework 3.5 and 4.8.1
The September 9, 2025 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
There 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. |
1Windows Presentation Foundation (WPF)
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: 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
- Help for installing updates: Windows Update FAQ
- Protect yourself online and at home: Windows Security support
- Local support according to your country: International Support