MS13-040: Description of the security update for the .NET Framework 4.5 on Windows 8, Windows RT, and Windows Server 2012: May 14, 2013


Resolves a vulnerability in the Microsoft .NET Framework that could allow identity spoofing on a client system.


Microsoft has released security bulletin MS13-040. You can view the complete security bulletin by going to one of the following Microsoft websites:

How to obtain help and support for this security update

Help installing updates: Support for Microsoft Update

Security solutions for IT professionals: TechNet Security Troubleshooting and Support

Help protect your Windows-based computer from viruses and malware: Virus Solution and Security Center

Local support according to your country: International Support

More Information

Known issues with this security update

  • Windows Update will not offer this security update to Windows RT-based computers until update 2808380 has been installed. For more information, click the following article number to view the article in the Microsoft Knowledge Base:
    2808380 Windows RT-based device cannot download software updates or Windows Store apps

Download information

This update is available for download from the Microsoft Download Center:

Command-line switches for this update

For information about the various command-line switches that are supported by this update, click the following article number to view the article in the Microsoft Knowledge Base:

2844699 Command-line switches for Microsoft .NET Framework security update packages

Restart information

This update does not require a system restart after you apply it unless files that are being updated are locked or are being used.

Update replacement information

This update does not replace any previously released update.

Update removal information

Note We do not recommend that you remove any security update.

To remove this update, use the Programs and Features item in Control Panel.

File information

The English (United States) version of this update installs files that have the attributes that are listed in the following tables. The dates and the times for these files are listed in Coordinated Universal Time (UTC). The dates and the times for these files on your local computer are displayed in your local time together with your current daylight saving time (DST) bias. Additionally, the dates and the times may change when you perform certain operations on the files.

Applies to

This article applies to the following:
  • Microsoft .NET Framework 4.5 when used with:
    • Windows 8
    • Windows RT
    • Windows Server 2012