===================================================================== CERT-Renater Note d'Information No. 2010/VULN279 _____________________________________________________________________ DATE : 03/08/2010 HARDWARE PLATFORM(S) : / OPERATING SYSTEM(S) : Windows XP, Windows Server 2003, Windows Vista, Windows Server 2008, Windows 7. ====================================================================== KB2286198 http://www.microsoft.com/technet/security/bulletin/MS10-046.mspx ______________________________________________________________________ Microsoft Security Bulletin MS10-046 - Critical Vulnerability in Windows Shell Could Allow Remote Code Execution (2286198) Published: August 02, 2010 Version: 1.0 General Information Executive Summary This security update resolves a publicly disclosed vulnerability in Windows Shell. The vulnerability could allow remote code execution if the icon of a specially crafted shortcut is displayed. An attacker who successfully exploited this vulnerability could gain the same user rights as the local user. 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. This security update is rated Critical for all supported editions of Microsoft Windows. For more information, see the subsection, Affected and Non-Affected Software, in this section. The security update addresses the vulnerability by correcting validation of shortcut icon references. For more information about the vulnerability, see the Frequently Asked Questions (FAQ) subsection for the specific vulnerability entry under the next section, Vulnerability Information. This security update addresses the vulnerability first described in Microsoft Security Advisory 2286198. Recommendation. The majority of 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. See also the section, Detection and Deployment Tools and Guidance, later in this bulletin. Affected and Non-Affected Software 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, visit Microsoft Support Lifecycle. Affected Software Operating System Maximum Security Impact Aggregate Severity Rating Bulletins Replaced by this Update Windows XP Service Pack 3 Remote Code execution Critical None Windows XP Professional x64 Edition Service Pack 2 Remote Code execution Critical None Windows Server 2003 Service Pack 2 Remote Code execution Critical None Windows Server 2003 x64 Edition Service Pack 2 Remote Code execution Critical None Windows Server 2003 with SP2 for Itanium-based Systems Remote Code execution Critical None Windows Vista Service Pack 1 and Windows Vista Service Pack 2 Remote Code execution Critical None Windows Vista x64 Edition Service Pack 1 and Windows Vista x64 Edition Service Pack 2 Remote Code execution Critical None Windows Server 2008 for 32-bit Systems and Windows Server 2008 for 32-bit Systems Service Pack 2* Remote Code execution Critical None Windows Server 2008 for x64-based Systems and Windows Server 2008 for x64-based Systems Service Pack 2* Remote Code execution Critical None Windows Server 2008 for Itanium-based Systems and Windows Server 2008 for Itanium-based Systems Service Pack 2 Remote Code execution Critical None Windows 7 for 32-bit Systems Remote Code execution Critical None Windows 7 for x64-based Systems Remote Code execution Critical None Windows Server 2008 R2 for x64-based Systems* Remote Code execution Critical None Windows Server 2008 R2 for Itanium-based Systems Remote Code execution Critical None *Server Core installation affected. This update applies, with the same severity rating, to supported editions of Windows Server 2008 or Windows Server 2008 R2 as indicated, whether or not installed using the Server Core installation option. For more information on this installation option, see the TechNet articles, Managing a Server Core Installation and Servicing a Server Core Installation. Note that the Server Core installation option does not apply to certain editions of Windows Server 2008 and Windows Server 2008 R2; see Compare Server Core Installation Options. Vulnerability Information Shortcut Icon Loading Vulnerability - CVE-2010-2568 A remote code execution vulnerability exists in affected versions of Microsoft Windows. The vulnerability exists because Windows incorrectly parses shortcuts in such a way that malicious code may be executed when the operating system displays the icon of a malicious shortcut file. An attacker who successfully exploited this vulnerability could run arbitrary code as the logged-on user. This update addresses a vulnerability previously discussed in Microsoft Security Advisory 2286198. To view this vulnerability as a standard entry in the Common Vulnerabilities and Exposures list, see CVE-2010-2568. Mitigating Factors for Shortcut Icon Loading Vulnerability - CVE-2010-2568 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: • An attacker who successfully exploits this vulnerability could gain the same user rights as the local user. 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. • For the USB removable device attack vector, when AutoPlay is disabled, the user would manually have to launch Windows Explorer or a similar application and browse to the affected folder of the removable disk. Workarounds for Shortcut Icon Loading Vulnerability - CVE-2010-2568 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: • Disable the displaying of icons for shortcuts Note See Microsoft Knowledge Base Article 2286198 to use the automated Microsoft Fix it solution to enable or disable this workaround. This Fix it solution requires a restart upon completion in order to be effective. This Fix it solution deploys the workaround, and thus has the same user impact. We recommend that administrators review the KB article closely prior to deploying this Fix it solution. Note Using Registry Editor incorrectly can cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that problems resulting from the incorrect use of Registry Editor can be solved. Use Registry Editor at your own risk. For information about how to edit the registry, view the "Changing Keys And Values" Help topic in Registry Editor (Regedit.exe) or view the "Add and Delete Information in the Registry" and "Edit Registry Data" Help topics in Regedt32.exe. 1. Click Start, click Run, type Regedit in the Open box, and then click OK. 2. Locate and then select the following registry key: HKEY_CLASSES_ROOT\lnkfile\shellex\IconHandler 3. Click the File menu and then click Export. 4. In the Export Registry File dialog box, enter LNK_Icon_Backup.reg and then click Save. Note This will create a backup of this registry key in the My Documents folder by default. 5. Select the value (Default) on the right pane in the Registry Editor. Press Enter to edit the value of the key. Delete the value, so that the value is blank, and press Enter. 6. Locate and then select the following registry key: HKEY_CLASSES_ROOT\piffile\shellex\IconHandler 7. Click the File menu and then click Export. 8. In the Export Registry File dialog box, enter PIF_Icon_Backup.reg and then click Save. Note This creates a backup of this registry key in the My Documents folder by default. 9. Select the value (Default) on the right pane in the Registry Editor. Press Enter to edit the value of the key. Delete the value, so that the value is blank, and press Enter. 10. Log all users off and on again, or restart the computer. Impact of workaround. Disabling icons from being displayed for shortcuts prevents the issue from being exploited on affected systems. When this workaround is implemented, the system may display most icons as a "white" default object icon, which does impact usability. We recommend that system administrators test this workaround thoroughly prior to deployment. When the workaround is undone, all icons will reappear. How to undo the workaround. Using the interactive method 1. Click Start, click Run, type Regedit in the Open box, and then click OK. 2. Click the File menu and then click Import. 3. In the Import Registry File dialog box, select LNK_Icon_Backup.reg, and then click Open. 4. Click the File menu and then click Import. 5. In the Import Registry File dialog box, select PIF_Icon_Backup.reg, and then click Open. 6. Exit Registry Editor, and then restart the computer. Manually resetting the Registry key values to the default values 1. Click Start, click Run, type Regedit in the Open box, and then click OK. 2. Locate and then click the following registry key: HKEY_CLASSES_ROOT\lnkfile\shellex\IconHandler 3. Reset the registry key value to: {00021401-0000-0000-C000-000000000046} 4. Locate and then click the following registry key: HKEY_CLASSES_ROOT\piffile\shellex\IconHandler 5. Reset the registry key value to: {00021401-0000-0000-C000-000000000046} 6. Restart the computer • Disable the WebClient service 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 Microsoft Office Outlook 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. To disable the WebClient Service, follow these steps: 1. Click Start, click Run, type Services.msc and then click OK. 2. Right-click WebClient service and select Properties. 3. Change the Startup type to Disabled. If the service is running, click Stop. 4. Click OK and exit the management application. 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. How to undo the workaround. To re-enable the WebClient Service, follow these steps: 1. Click Start, click Run, type Services.msc and then click OK. 2. Right-click WebClient service and select Properties. 3. Change the Startup type to Automatic. If the service is not running, click Start. 4. Click OK and exit the management application. • Block the download of LNK and PIF files from the Internet Blocking the download of LNK and PIF files on the Internet Gateway provides protection against remote exploitation of these attacks. Note that the files can be transferred over WebDAV, so any blocking solution should take this protocol into account. • Block outbound SMB connections on the perimeter firewall Blocking outbound SMB connections on the perimeter firewall reduces the risk of remote exploitation using file shares. ====================================================================== ========================================================= Les serveurs de référence du CERT-Renater http://www.urec.fr/securite http://www.cru.fr/securite http://www.renater.fr ========================================================= + CERT-RENATER | tel : 01-53-94-20-44 + + 151 bd de l'Hopital | fax : 01-53-94-20-41 + + 75013 Paris | email: certsvp@renater.fr + =========================================================