NY.gov Portal State Agency Listing
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:
2012-087

DATE(S) ISSUED:
11/13/2012

SUBJECT:
Vulnerabilities in .NET Framework Could Allow Remote Code Execution (MS12-074)

OVERVIEW:

Five vulnerabilities have been discovered in the Microsoft .NET framework, some of 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. These vulnerabilities can be exploited if a user visits or is redirected to a specially crafted web page, runs a specially crafted Microsoft .NET application, or loads a specially crafted proxy configuration file.

Successful exploitation of these vulnerabilities could allow the attacker to obtain complete control of the affected system. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights.

SYSTEMS AFFECTED:

  • Microsoft .NET Framework 1.0
  • Microsoft .NET Framework 1.1
  • Microsoft NET Framework 2.0
  • Microsoft .NET Framework 3.5
  • Microsoft .NET Framework 3.5.1
  • Microsoft .NET Framework 4
  • Microsoft .NET Framework 4.5

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:
Five vulnerabilities have been discovered in the Microsoft .NET Framework, details of which are described below:

Reflection Bypass Vulnerability (CVE-2012-1895) - A privilege escalation vulnerability exists in the .NET framework due to the improper validation of permissions for objects performing reflection.  Exploitation could occur if a user visits a website that hosts specially crafted XBAP (Extensible Application Markup Language Browser Application) content using Internet Explorer. Additionally, an attacker can exploit this issue by creating a specially crafted Windows .NET application to bypass Code Access Security (CAS) restrictions.

Web Reflection Optimization Vulnerability (CVE-2012-4777) - An elevation of privilege vulnerability exists in the way that the .NET framework validates permissions for objects involved with reflection. Exploitation could occur if a user visits a website that hosts specially crafted XBAP (Extensible Application Markup Language Browser Application) content using Internet Explorer. Additionally, an attacker can exploit this issue by creating a specially crafted Windows .NET application to bypass Code Access Security (CAS) restrictions.

Code Access Security Information Disclosure (CVE-2012-1896) - An information disclosure vulnerability exists in the Microsoft .NET framework due to the improper sanitation of output when a function is called from partially trusted code. Exploitation could occur if a user visits a website that hosts specially crafted XBAP (Extensible Application Markup Language Browser Application) content using Internet Explorer. Additionally, an attacker can exploit this issue by creating a specially crafted Windows .NET application to bypass Code Access Security (CAS) restrictions. Successful exploitation could result in the disclosure of sensitive information.

.NET Framework Insecure Library Loading (CVE-2012-2519) - A remote code execution vulnerability exists in the way the .NET framework restricts the path for loading external libraries. Exploitation may occur if an attacker convinces a user to open a .NET application that resides in the same directory as a specially crafted Dynamic Link Library (DLL) file.

Web Proxy Auto-Discovery Vulnerability (CVE-2012-4776) - A remote code execution vulnerability exists in the way the .NET framework retrieves the default web proxy settings. Exploitation may occur if an attacker performs a man in the middle attack and provides the end user with a specially crafted proxy detection file that contains client side code in the form of JavaScript.

Successful exploitation of these vulnerabilities could result in the execution of the attacker supplied code and allow the attacker to obtain complete control of the affected system. 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.
  • Run all software as a non-privileged user (one without administrative privileges) to diminish the effects of a successful attack.
  • Remind users not to visit un-trusted websites or follow links provided by unknown or un-trusted sources.
  • Unless there is a business need to do otherwise, consider disabling XAML browser applications (XBAP) in Internet Explorer.

REFERENCES:
Microsoft:
http://technet.microsoft.com/en-us/security/bulletin/ms12-074
http://technet.microsoft.com/en-us/security/advisory/2269637

CVE:
http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2012-1895
http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2012-1896
http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2012-2519
http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2012-4776
http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2012-4777

Security Focus:
http://www.securityfocus.com/bid/56455
http://www.securityfocus.com/bid/56456
http://www.securityfocus.com/bid/56462
http://www.securityfocus.com/bid/56463
http://www.securityfocus.com/bid/56464