Microsoft Support:
The October 14, 2025 update for Windows 11, version 24H2 and Microsoft server operating system version 24H2 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 ImprovementsCVE-2025-55248 - .NET Framework Information Disclosure vulnerability
This security update addresses an information disclosure vulnerability detailed in CVE-2025-55248.
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: Windows 11, version 24H2 and Microsoft server operating system version 24H2 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. Source:
October 14, 2025-KB5066131 Cumulative Update for .NET Framework 3.5 and 4.8.1 for Windows 11, version 24H2 and Microsoft server operating system version 24H2 | Microsoft Support
October 14, 2025-KB5066131 Cumulative Update for .NET Framework 3.5 and 4.8.1 for Windows 11, version 24H2 and Microsoft server operating system version 24H2
support.microsoft.com
.NET and .NET Framework October 2025 servicing releases updates - .NET Blog
A recap of the latest servicing updates for .NET and .NET Framework for October 2025.
devblogs.microsoft.com
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