Kernel For Outlook Express

[Manlio Chowdhury]

This security update resolves three privately reported vulnerabilities and one publicly disclosed vulnerability in Microsoft Windows. The most severe of these vulnerabilities could allow elevation of privilege if an attacker logs on to the system and runs a specially crafted application. An attacker must have valid logon credentials and be able to log on locally to exploit the most severe vulnerabilities.

This security update is rated Important for all supported releases of Microsoft Windows. For more information, see the subsection, Affected and Non-Affected Software, in this section.

The security update addresses the vulnerabilities by correcting the way that the Windows kernel-mode driver handles objects in memory. For more information about the vulnerabilities, 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 at the earliest opportunity using update management software, or by checking for updates using the Microsoft Update service.

The following software have been tested to determine which versions or editions are affected. Other versions or editions are either past their support life cycle or are not affected. To determine the support life cycle for your software version or edition, see Microsoft Support Lifecycle.

What if I experienced difficulties restartingmy system after installing security update 2823324?
To help customers who are experiencing difficulties restarting their systems after installation of security update 2823324, Microsoft is making available a bootable media ISO image through the Microsoft Download Center (DLC). Customers who cannot successfully restart their systems after applying the 2823324 update can download this image to create a bootable DVD or USB drive with which they can boot their systems, uninstall security update 2823324, and return their systems to a normal operating state. Please see the Microsoft Download Center for additional guidance and to download the ISO.

Microsoft recommends using this ISO image only if customers cannot successfully restart their systems. Customers who can restart normally should not use this ISO image and should instead refer to Microsoft Knowledge Base Article 2839011 for instructions on how to uninstall security update 2823324.

Why was this bulletin revised on April 11, 2013?
Microsoft revised this bulletin to address known issues associated with installation of security update 2823324. Microsoft is investigating behavior where systems may fail to recover from a restart or where applications fail to load after this security update is applied. Microsoft recommends that customers uninstall this update. As an added precaution, Microsoft has removed the download links to the 2823324 security update. For instructions on how to uninstall this update, see Microsoft Knowledge Base Article 2839011.

Why does this update address several reported security vulnerabilities?
This update contains support for several vulnerabilities because the modifications that are required to address these issues are located in related files.

There are multiple update packages available for some affected software. Do I need to install all the updates listed in the Affected Software table for the software?
Yes. Customers should apply all updates offered for the software installed on their systems.

Do I need to install these security updates in a particular sequence?
No. Multiple updates for one version of Microsoft Windows or Microsoft Windows Server software can be applied in any sequence.

I am using an older release of the software discussed in this security bulletin. What should I do?
The affected software listed in this bulletin have been tested to determine which releases are affected. Other releases are past their support life cycle. For more information about the product lifecycle, see the Microsoft Support Lifecycle website.

It should be a priority for customers who have older releases of the software to migrate to supported releases to prevent potential exposure to vulnerabilities. To determine the support lifecycle for your software release, see Select a Product for Lifecycle Information. For more information about service packs for these software releases, see Service Pack Lifecycle Support Policy.

Customers who require custom support for older software must contact their Microsoft account team representative, their Technical Account Manager, or the appropriate Microsoft partner representative for custom support options. Customers without an Alliance, Premier, or Authorized Contract can contact their local Microsoft sales office. For contact information, see the Microsoft Worldwide Information website, select the country in the Contact Information list, and then click Go to see a list of telephone numbers. When you call, ask to speak with the local Premier Support sales manager. For more information, see the Microsoft Support Lifecycle Policy FAQ.

The following severity ratings assume the potential maximum impact of the vulnerability. For information regarding the likelihood, within 30 days of this security bulletin's release, of the exploitability of the vulnerability in relation to its severity rating and security impact, please see the Exploitability Index in the April bulletin summary. For more information, see Microsoft Exploitability Index.

An elevation of privilege vulnerability exists when the Windows kernel-mode driver improperly handles objects in memory. An attacker who successfully exploited this vulnerability could gain elevated privileges and read arbitrary amounts of kernel memory.

Mitigation refers to a setting, common configuration, or general best-practice, existing in a default state, that could reduce the severity of exploitation of a vulnerability. The following mitigating factors may be helpful in your situation:

What is the Windows kernel-mode driver (win32k.sys)?
Win32k.sys is a kernel-mode device driver and is the kernel part of the Windows subsystem. It contains the window manager, which controls window displays; manages screen output; collects input from the keyboard, mouse, and other devices; and passes user messages to applications. It also contains the Graphics Device Interface (GDI), which is a library of functions for graphics output devices. Finally, it serves as a wrapper for DirectX support that is implemented in another driver (dxgkrnl.sys).

What is the Windows kernel?
The Windows kernel is the core of the operating system. It provides system-level services such as device management and memory management, allocates processor time to processes, and manages error handling.

What might an attacker use the vulnerability to do?
An attacker who successfully exploited this vulnerability could gain elevated privileges and read arbitrary amounts of kernel memory.

How could an attacker exploit the vulnerability?
To exploit this vulnerability, an attacker would first have to log on to the system. An attacker could then run a specially crafted application designed to increase privileges.

What systems are primarily at risk from the vulnerability?
Workstations and terminal servers are primarily at risk. Servers could be at more risk if administrators allow users to log on to servers and to run programs. However, best practices strongly discourage allowing this.

When this security bulletin was issued, had this vulnerability been publicly disclosed?
No. Microsoft received information about this vulnerability through coordinated vulnerability disclosure.

When this security bulletin was issued, had Microsoft received any reports that this vulnerability was being exploited?
No. Microsoft had not received any information to indicate that this vulnerability had been publicly used to attack customers when this security bulletin was originally issued.

Workaround refers to a setting or configuration change that does not correct the underlying vulnerability but would help block known attack vectors before you apply the update. Microsoft has tested the following workarounds and states in the discussion whether a workaround reduces functionality:

Disabling the WebClient service helps protect affected systems from attempts to exploit this vulnerability by blocking the most likely remote attack vector through the Web Distributed Authoring and Versioning (WebDAV) client service. After applying this workaround it is still possible for remote attackers who successfully exploit this vulnerability to cause the system to run programs located on the targeted user's computer or the Local Area Network (LAN), but users will be prompted for confirmation before opening arbitrary programs from the Internet.

Impact of workaround. When the WebClient service is disabled, Web Distributed Authoring and Versioning (WebDAV) requests are not transmitted. In addition, any services that explicitly depend on the Web Client service will not start, and an error message will be logged in the System log. For example, WebDAV shares will be inaccessible from the client computer.

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