Applies to:
Microsoft .NET Framework 4.8
Windows Server 2008 R2 SP1 Extended Security Updates (ESU) third and final year ended on January 10, 2023. Additionally, Extended Security Updates on Azure only support ended on January 9, 2024. For more information, see Extended Security Updates for Windows Server overview.
We recommend that you upgrade to a later version of Windows Server. For more information, see Overview of Windows Server upgrades.
Summary
The October 14, 2025 update for Windows Server 2008 R2 SP1 includes cumulative security and reliability improvements in .NET Framework 4.8.
Note Starting in July 2020, there will no longer be optional, non-security releases (known as "C" releases) for this operating system. Operating systems in extended support have only cumulative monthly security updates (known as the "B" or Update Tuesday release).
Verify that you have installed the required updates listed in the How to get this update section before installing this update.　
Customers who have purchased the Extended Security Update (ESU) for on-premises versions of these operating systems must follow the procedures in KB4522133 to continue receiving security updates after extended support ends on January 14, 2020.　For more information on ESU and which editions are supported, see KB4497181. For more information, see the ESU blog.
Security Improvements
CVE-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.
Additional information about this update
The following articles contain additional information about this update as it relates to individual product versions.
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5066739 Description of the Security and Quality Rollup for .NET Framework 3.5.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8 for Windows Server 2008 R2 SP1 (KB5066739)
Known issues in this update
Microsoft is not currently aware of any issues in this update.
How to get this update
Before installing this update
To apply this update, you must have .NET Framework 4.8 installed.
You must install the updates listed below and restart your device before installing the latest Rollup. Installing these updates improves the reliability of the update process and mitigates potential issues while installing the Rollup and applying Microsoft security fixes.
We strongly recommend that you install the latest servicing stack update (SSU) for your operating system before installing the latest Rollup. SSUs improve the reliability of the update process to mitigate potential issues while installing the Rollup and applying Microsoft security fixes. For general information about SSUs, see Servicing stack updates and Servicing Stack Updates (SSU): Frequently Asked Questions.
If you use Windows Update, the latest SSU (KB5039339) will be offered to you automatically. To get the standalone package for the latest SSU, search for it in the Microsoft Update Catalog.
Language packs
If you install a language pack after you install this update, you must reinstall this update. Therefore, we recommend that you install any language packs that you need before you install this update. For more information, see Add language packs to Windows.
Install this update
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Release Channel |
Available |
Next Step |
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Windows Update and Microsoft Update |
Yes |
None. This update will be downloaded and installed automatically from Windows Update if you are an ESU customer. |
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Microsoft Update Catalog |
Yes |
To get the standalone package for this update, go to the Microsoft Update Catalog website. |
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Windows Server Update Services (WSUS) |
Yes |
This individual .NET Framework product update will be installed, as applicable, by applying the operating system update. For more information about operating system updates see additional information about this update section. |
Restart requirement
You may need to 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.
Update deployment information
For deployment details for this security update, see the Deployments tab of the Microsoft Security Response Center (MSRC) Security Update Guide.
Update replacement information
This update replaces previously released updates KB5050183 and KB5065958.
File Information
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x86 |
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x64 |
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How to obtain help and support for this update
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Help for installing updates: Windows Update FAQ
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Protect yourself online and at home: Windows Security support
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Local support according to your country: International Support
