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The Microsoft .NET Framework 4.5.1 Hotfix Rollup KB2909239 (Offline Installer) is now available for the .NET Framework 4, the .NET Framework 4.5, and the .NET Framework 4.5.1. This offline installer applies to Windows Vista, Windows 7, Windows 8, Windows 8.1, Windows Server 2008, Windows Server 2008 R2, Windows Server 2012, and Windows Server 2012 R2. 

More Information

Hotfix information

A supported hotfix is now available from Microsoft. However, it is intended to correct only the problem that is described in this article. Apply it only to systems that are experiencing this specific problem. This hotfix may receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next that contains this hotfix.

To resolve this problem immediately, contact Microsoft Customer Support Services to obtain the hotfix. For a complete list of Microsoft Customer Support Services telephone numbers and information about support costs, visit the following Microsoft website: In special cases, charges that are ordinarily incurred for support calls may be canceled if a Microsoft Support Professional determines that a specific update will resolve your problem. The usual support costs will apply to additional support questions and issues that do not qualify for the specific update in question.

For more information about how to download Microsoft support files, click the following article number to view the article in the Microsoft Knowledge Base:

119591 How to obtain Microsoft support files from online services Microsoft scanned this file for viruses. Microsoft used the most current virus-detection software that was available on the date that the file was posted. The file is stored on security-enhanced servers that help prevent any unauthorized changes to the file.

What is new in the .NET Framework 4.5.1 Hotfix Rollup KB2909239?

The following KBs contain information about individual fixes:

2908383 Hotfix rollup 2908383 is available for the .NET Framework 4.5.1 on Windows Vista SP2, Windows 7 SP1, Windows Server 2008 SP2 and Windows Server 2008 R2 SP1

2908385 Hotfix rollup 2908385 is available for the .NET Framework 4.5.1 on Windows 8 and Windows Server 2012

2908387 Hotfix rollup 2908387 is available for the .NET Framework 4.5.1 on Windows 8.1 and Windows Server 2012 R2

Note Customers who are running on non-English operating systems will have to download the .NET Framework 4.5.1 Language Packs if these are not already present on their system. The .NET Framework 4.5.1 Hotfix Rollup KB2909239 uses the same Language Packs that were released with the .NET Framework 4.5.1.

For more information about the .NET Framework 4.5.1 Language Packs, go to the following Microsoft Download Center website:

The .NET Framework 4.5.1 Language Packs (Offline Installer)

Note You must download and install the .NET Framework 4.5.1 Hotfix Rollup KB2909239 (Offline Installer) before you install the language packs.

Command-line options for this update

For more information about the various command-line options that are supported by this update, go to the "Command-Line options" section on the following MSDN website:

.NET Framework Deployment Guide for Developers

Restart requirement

You may have to restart the computer after you install this update. We recommend that you close all applications that are using the .NET Framework before you install this update.


Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

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