Description: This security update resolves three privately reported vulnerabilities in Microsoft .NET Framework and Microsoft Silverlight. The vulnerabilities could allow remote code execution on a client system if a user views a specially crafted Web page using a Web browser that can run XAML Browser Applications (XBAPs) or Silverlight applications, or if an attacker succeeds in persuading a user to run a specially crafted Microsoft .NET application. Users whose accounts are configured to have fewer user rights on the system could be less impacted than users who operate with administrative user rights. The vulnerabilities could also allow remote code execution on a server system running IIS, if that server allows processing ASP.NET pages and an attacker succeeds in uploading a specially crafted ASP.NET page to that server and executing it, as could be the case in a Web hosting scenario. Microsoft .NET applications, Silverlight applications, XBAPs and ASP.NET pages that are not malicious are not at risk of being compromised because of this vulnerability. The security update addresses the vulnerabilities by modifying the way in which the Microsoft .NET verifies and enforces the rules of Microsoft .NET verifiable code and by modifying the way in which the Microsoft .NET Common Language Runtime (CLR) handles interfaces.

Update type: Critical

Release date: October 13, 2009

Applies to: All versions

Knowledge base: support.microsoft.com/kb/974378

Download link: 32-bit | 64-bit
Comments:Here are the specifics on the vulnerabilities covered by this update:

• Microsoft .NET Framework Pointer Verification Vulnerability – CVE-2009-0090
• Microsoft .NET Framework Type Verification Vulnerability – CVE-2009-0091
• Microsoft Silverlight and Microsoft .NET Framework CLR Vulnerability – CVE-2009-2497