This article describes hotfix rollup 2966780 for the Microsoft .NET Framework 3.5. This hotfix rollup fixes several issues in the .NET Framework 3.5. For more information about the issue that the hotfix rollup resolves, see the "More Information" section.

This hotfix rollup is available for the following operating systems:

  • Windows 8

  • Windows Server 2012

More Information

Hotfix Information

A supported hotfix is now available from Microsoft. However, it is intended to correct only the problem that this article describes. Apply it only to systems that are experiencing this specific problem.

To resolve this problem, 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.


To apply this hotfix, you must have the .NET Framework 3.5 installed.

Restart requirement

You have to restart the computer after you apply this hotfix if any affected files are being used. We recommend that you exit all .NET Framework-based applications before you apply this hotfix.

Hotfix replacement information

This hotfix package does not replace a previously released hotfix package.

The global version of this hotfix has the file attributes (or later file attributes) that are listed in the following table. The dates and times for these files are listed in Coordinated Universal Time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time item in Control Panel.

For all supported x86-based versions of the .NET Framework 3.5 in Windows 8 and Windows Server 2012

For all supported x64-based versions of the .NET Framework 3.5 in Windows 8 and Windows Server 2012

Issue that this hotfix rollup resolves

Issue 1

Assume that you run a Microsoft .NET Framework 2.0 Service Pack 2 (SP2)-based application or a Microsoft .NET Framework 3.5-based application to obtain the new currency symbol for the Russian Ruble. If the user locale for the computer is set to a non-Russian locale, the new Russian Ruble symbol is not displayed.

Issue 2

When you update an affected system to Visual Studio 2012 Update 2 on a .NET Framework 3.5-based application, you receive the following error message:

An unhandled exception of type 'System.ExecutionEngineException' occurred in mscorlib.dll

This issue occurs because an assembly is not validated by the Assembly Loader. This is because some assembly dependencies cannot be validated correctly by some policies that resolve dependencies in the .NET Framework.

Issue 3You encounter high CPU usage when you run a .NET Framework 3.5 or Microsoft SharePoint 2010-based application on servers that contain more than 16 processors and the processor load cannot be attributed to application workload. 

The .NET Framework 3.5 was not optimized for large multiprocessor servers. The following environment variable may reduce some CPU load. However, we recommend that you do not apply these settings until the application performance characteristics are fully understood and until all application workloads are fully accounted for.

Environment Variable


Recommended Setting


Sets how many processors to use for certain Runtime calculations. Default value is the actual processor count.

A value from 2 to 8.

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