This article describes a hotfix for the Microsoft .NET Framework 4.5 that resolves an ASP.NET race condition issue in the following operating systems:
Windows Server 2012
When you run the Internet Information Services (IIS) worker process (w3wp.exe) in an integrated pipeline mode, the process may crash or experience a deadlock. This issue occurs because of an unhandled NullReferenceException exception in the ASP.NET code.
The deadlock may occur if there is a managed module that listens to the PreSendRequestHeaders or PreSendRequestContent notification. The deadlock occurs because of a race condition in the ASP.NET code that handles the SendResponse notifications that are triggered by the native IIS modules (for example, the Microsoft Application Request Routing [ARR] module).
The process may crash when a site is used under a high load and the site serves requests to the asynchronous pages or asynchronous handlers or when the pipeline has asynchronous modules. This behavior occurs because of the way that a race condition in the ASP.NET code responds when the code completes the asynchronous operations.
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, go to the following Microsoft website:
Note 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 4.5 installed on Windows 8, Windows RT, or Windows Server 2012.
You may have to restart the computer after you apply this hotfix if any affected files are being used. We recommend that you close all .NET Framework 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.