A hotfix is available for the .NET Framework 4.5 which resolves several issues that occur when you use the HttpWebRequest and SslStream classes


This article describes a hotfix that resolves issues in the Microsoft .NET Framework 4.5. 

More Information

Issues that this hotfix resolves

Issue 1

When you use a .NET Framework 4.5-based application that uses asynchronous APIs in order to read chunked responses, the chunked responses may be read synchronously.

Cause 1

The HttpWebRequest class enables callers to read an HTTP response either synchronously or asynchronously. However, if the response is a chunked HTTP response, then parts of the response are read by using synchronous I/O (Winsock calls) even when the caller uses the asynchronous code path. This results in the calling thread being blocked until data is received on the network.

Issue 2

Assume that you have a .NET Framework 4.5-based application that communicates with a server over the Transport Layer Security/Secure Sockets Layer (TLS/SSL) protocol by using the HttpWebRequest or SslStream class. If the server requests an SSL renegotiation while the application is sending data, the application may encounter an unhandled exception and crash.

Issue 3

A thread pool freezes in the HttpWebRequest class if an HTTPS request is aborted during an SSL renegotiation while a write operation is pending.

Cause 3

This issue occurs because of a race condition that may occur when the HttpWebRequest class or the SslStream class handles SSL renegotiation. This may result in the thread pool creating more and more threads. Additionally, the resources that are held in memory are not cleared.


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: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 a computer that is running one of the following operating systems:
  • Windows 8
  • Windows RT
  • Windows Server 2012

Restart requirement

You must restart the computer after you install the hotfix if the affected files are being used during the installation. We recommend that you close all applications that use the .NET Framework before you install the hotfix.

File information

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 4.5

File nameFile versionFile sizeDateTimePlatform
For all supported x64-based versions of the .NET Framework 4.5
File nameFile versionFile sizeDateTimePlatform


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


For more information about the HttpWebRequest class, go to the following MSDN website: For more information about the SslStream class, go to the following MSDN website:

ID d'article : 2745583 - Dernière mise à jour : 1 nov. 2012 - Révision : 1