This security update resolves a privately reported vulnerability in Microsoft Windows. The vulnerability could allow remote code execution if an attacker sends a specially crafted web request to an ASP.NET web application running on an affected system. An attacker could exploit this vulnerability without authentication to run arbitrary code.
This security update is rated Critical for all supported 64-bit editions of Microsoft Windows. This security update has no severity rating for Windows RT and for all supported 32-bit editions of Windows Server 2003, Windows Vista, Windows Server 2008, Windows 7, and Windows 8. For more information, see the subsection, Affected and Non-Affected Software, in this section.
The security update addresses the vulnerability by correcting the way that the Windows common control library allocates memory for data structures. For more information about the vulnerability, see the Frequently Asked Questions (FAQ) subsection for the specific vulnerability entry under the next section, Vulnerability Information.
Recommendation. Most customers have automatic updating enabled and will not need to take any action because this security update will be downloaded and installed automatically. Customers who have not enabled automatic updating need to check for updates and install this update manually. For information about specific configuration options in automatic updating, see Microsoft Knowledge Base Article 294871.
For administrators and enterprise installations, or end users who want to install this security update manually, Microsoft recommends that customers apply the update immediately using update management software, or by checking for updates using the Microsoft Update service.