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The following cyber advisory was issued by the New York State Office of Information Technology Services and is intended for State government entities. The information may or may not be applicable to the general public and, accordingly, the State does not warrant its use for any specific purposes.

ITS ADVISORY NUMBER:
2012-012

DATE(S) ISSUED:
02/14/2012

SUBJECT:
Vulnerabilities in .NET Framework and Microsoft Silverlight Could Allow Remote Code Execution (MS12-016)

OVERVIEW:

Two vulnerabilities have been discovered in the Microsoft .NET Framework and Microsoft Silverlight which could allow an attacker to take complete control of an affected system. Microsoft .NET is a software framework for applications designed to run under Microsoft Windows. Microsoft Silverlight is a web application framework that provides support for .NET applications and is used for streaming media. The vulnerabilities can be exploited if a user visits or is redirected to a specially crafted web page, or runs a specially crafted Microsoft .NET or Silverlight application.

Successful exploitation could result in an attacker gaining the same privileges as the logged on user. Depending on the privileges associated with the user, an attacker could then install programs; view, change, or delete data; or create new accounts with full user rights.

SYSTEMS AFFECTED:

  • Microsoft Silverlight 4
  • Microsoft .NET Framework 2.0
  • Microsoft .NET Framework 3.5.1
  • Microsoft .NET Framework 4.0

RISK:
Government:

  • Large and medium government entities: High
  • Small government entities: High

Businesses:

  • Large and medium business entities: High
  • Small business entities: High

Home users: High

DESCRIPTION:
Two vulnerabilities have been discovered in the Microsoft .NET Framework and Microsoft Silverlight which could allow an attacker to take complete control of an affected system. The
first vulnerability is caused by .NET and Silverlight improperly handling objects in memory. The second vulnerability is caused by the program incorrectly setting a buffer length while parsing user input. The vulnerabilities can be exploited through the following attack scenarios:

In the first scenario, an attacker uploads specially crafted ASP.NET code to a web server that hosts user-created content. Successful exploitation could result in the attacker gaining the same privileges as the service account associated with the application pool identity. Depending on the privileges granted to the service account and on the application pool configuration, an attacker might be able to take control of other application pools on the web server or be able to take complete control of the affected system.

In the second scenario, exploitation could occur if a user visits a specially crafted website that hosts specially crafted XBAP (Extensible Application Markup Language Browser Application) content. Successful exploitation could result in an attacker gaining the same privileges as the logged on user. Depending on the privileges associated with the user, an attacker could then install programs; view, change, or delete data; or create new accounts with full user rights.

In the third scenario, an attacker can exploit this issue by creating Windows .NET applications to bypass Code Access Security (CAS) restrictions. Successful exploitation could result in an attacker gaining the same privileges as the logged on user. Depending on the privileges associated with the user, an attacker could then install programs; view, change, or delete data; or create new accounts with full user rights.

RECOMMENDATIONS:
We recommend the following actions be taken:

  • Apply appropriate patches provided by Microsoft to vulnerable systems immediately after appropriate testing.
  • Remind users not to visit un-trusted websites or follow links provided by unknown or un-trusted sources.
  • Run all software as a non-privileged user (one without administrative privileges) to diminish the effects of a successful attack.
  • Apply the principle of Least Privilege to all services.
  • Unless there is a business need to do otherwise, consider disabling XAML browser applications in Internet Explorer.

REFERENCES:
Microsoft:
http://technet.microsoft.com/en-us/security/bulletin/ms12-016

CVE:
http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2012-0014
http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2012-0015