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Virus Encyclopedia

Welcome to the Virus Encyclopedia of Panda Security.

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Threat LevelLow threatDamageHighDistributionNot widespread
Affected platforms:

Windows 2003/XP/2000/NT

worm, Trojan or backdoor. It is a group of critical vulnerabilities in the .NET Common Language Runtime and Silverlight, which allows arbitrary code to be remotely executed in the vulnerable computer.

The Common Language Runtime (CLR) is a run-time environment provided by the .NET Framework which makes the development process easier.

The affected components are:

  • .NET Framework 3.5.1 on Windows 2008 R2/7.
  • .NET Framework 3.5 on Windows 2008/Vista/2003/XP.
  • .NET Framework 2.0 on Windows 2008/Vista/2003/XP.
  • Silverlight 2 and 3.


This vulnerability can be exploited using different means:

  • By hosting a specially crafted website that contains a specially crafted XBAP (XAML browser application) and enticing users to visit it.
  • By uploading a malicious ASP.NET application to a web hosting environment.
  • By placing a malicious .NET Framework application on a network share and enticing users to execute it.


If you have any of the vulnerable components, it is recommended to download and apply the security patch for this vulnerability. Click here to access the web page for downloading the patch.

Bear in mind that this security bulletin replaces a previous one, called MS09-061.