===================================================================== CERT-Renater Note d'Information No. 2010/VULN034 _____________________________________________________________________ DATE : 15/01/2010 HARDWARE PLATFORM(S) : / OPERATING SYSTEM(S) : Systems running Internet Explorer version 6, 7, 8. ====================================================================== http://www.microsoft.com/technet/security/advisory/979352.mspx ______________________________________________________________________ Microsoft Security Advisory (979352) Vulnerability in Internet Explorer Could Allow Remote Code Execution Published: January 14, 2010 Version: 1.0 General Information Executive Summary Microsoft is investigating a report of a publicly exploited vulnerability in Internet Explorer. This advisory contains information about which versions of Internet Explorer are vulnerable as well as workarounds and mitigations for this issue. Our investigation so far has shown that Internet Explorer 5.01 Service Pack 4 on Microsoft Windows 2000 Service Pack 4 is not affected, and that Internet Explorer 6 Service Pack 1 on Microsoft Windows 2000 Service Pack 4, and Internet Explorer 6, Internet Explorer 7 and Internet Explorer 8 on supported editions of Windows XP, Windows Server 2003, Windows Vista, Windows Server 2008, Windows 7, and Windows Server 2008 R2 are affected. The vulnerability exists as an invalid pointer reference within Internet Explorer. It is possible under certain conditions for the invalid pointer to be accessed after an object is deleted. In a specially-crafted attack, in attempting to access a freed object, Internet Explorer can be caused to allow remote code execution. At this time, we are aware of limited, active attacks attempting to use this vulnerability against Internet Explorer 6. We have not seen attacks against other affected versions of Internet Explorer. We will continue to monitor the threat environment and update this advisory if this situation changes. On completion of this investigation, Microsoft will take the appropriate action to protect our customers, which may include providing a solution through our monthly security update release process, or an out-of-cycle security update, depending on customer needs. We are actively working with partners in our Microsoft Active Protections Program (MAPP) and our Microsoft Security Response Alliance (MSRA) programs to provide information that they can use to provide broader protections to customers. In addition, were actively working with partners to monitor the threat landscape and take action against malicious sites that attempt to exploit this vulnerability. Microsoft continues to encourage customers to follow the "Protect Your Computer" guidance of enabling a firewall, applying all software updates and installing anti-virus and anti-spyware software. Additional information can be found at Security at home. Mitigating Factors Protected Mode in Internet Explorer on Windows Vista and later Windows operating systems limits the impact of the vulnerability. In a Web-based attack scenario, an attacker could host a Web site that contains a Web page that is used to exploit this vulnerability. In addition, compromised Web sites and Web sites that accept or host user-provided content or advertisements could contain specially crafted content that could exploit this vulnerability. In all cases, however, an attacker would have no way to force users to visit these Web sites. Instead, an attacker would have to convince users to visit the Web site, typically by getting them to click a link in an e-mail message or Instant Messenger message that takes users to the attackers Web site. 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 affected than users who operate with administrative user rights. By default, Internet Explorer on Windows Server 2003 and Windows Server 2008 runs in a restricted mode that is known as Enhanced Security Configuration. This mode sets the security level for the Internet zone to High. This is a mitigating factor for Web sites that you have not added to the Internet Explorer Trusted sites zone. By default, all supported versions of Microsoft Outlook, Microsoft Outlook Express, and Windows Mail open HTML e-mail messages in the Restricted sites zone. The Restricted sites zone helps mitigate attacks that could try to exploit this vulnerability by preventing Active Scripting and ActiveX controls from being used when reading HTML e-mail messages. However, if a user clicks a link in an e-mail message, the user could still be vulnerable to exploitation of this vulnerability through the Web-based attack scenario. Affected Software Microsoft Windows 2000 Service Pack 4 Windows XP Service Pack 2 and Windows XP Service Pack 3 Windows XP Professional x64 Edition Service Pack 2 Windows Server 2003 Service Pack 2 Windows Server 2003 x64 Edition Service Pack 2 Windows Server 2003 with SP2 for Itanium-based Systems Windows Vista, Windows Vista Service Pack 1, and Windows Vista Service Pack 2 Windows Vista x64 Edition, Windows Vista x64 Edition Service Pack 1, and Windows Vista x64 Edition Service Pack 2 Windows Server 2008 for 32-bit Systems and Windows Server 2008 for 32-bit Systems Service Pack 2 Windows Server 2008 for x64-based Systems and Windows Server 2008 for x64-based Systems Service pack 2 Windows Server 2008 for Itanium-based Systems and Windows Server 2008 for Itanium-based Systems Service Pack 2 Windows 7 Windows 7 for x64-based Systems Windows Server 2008 R2 for x64-based Systems Windows Server 2008 R2 for Itanium-based Systems Internet Explorer 6 Service Pack 1 on Microsoft Windows 2000 Service Pack 4 Internet Explorer 6 for Windows XP Service Pack 2, Windows XP Service Pack 3, and Windows XP Professional x64 Edition Service Pack 2 Internet Explorer 6 for Windows Server 2003 Service Pack 2, Windows Server 2003 with SP2 for Itanium-based Systems, and Windows Server 2003 x64 Edition Service Pack 2 Internet Explorer 7 for Windows XP Service Pack 2 and Windows XP Service Pack 3, and Windows XP Professional x64 Edition Service Pack 2 Internet Explorer 7 for Windows Server 2003 Service Pack 2, Windows Server 2003 with SP2 for Itanium-based Systems, and Windows Server 2003 x64 Edition Service Pack 2 Internet Explorer 7 in Windows Vista, Windows Vista Service Pack 1, Windows Vista Service Pack 2, Windows Vista x64 Edition, Windows Vista x64 Edition Service Pack 1, and Windows Vista x64 Edition Service Pack 2 Internet Explorer 7 in Windows Server 2008 for 32-bit Systems and Windows Server 2008 for 32-bit Systems Service Pack 2 Internet Explorer 7 in Windows Server 2008 for Itanium-based Systems and Windows Server 2008 for Itanium-based Systems Service Pack 2 Internet Explorer 7 in Windows Server 2008 for x64-based Systems and Windows Server 2008 for x64-based Systems Service Pack 2 Internet Explorer 8 for Windows XP Service Pack 2, Windows XP Service Pack 3, and Windows XP Professional x64 Edition Service Pack 2 Internet Explorer 8 for Windows Server 2003 Service Pack 2, and Windows Server 2003 x64 Edition Service Pack 2 Internet Explorer 8 in Windows Vista, Windows Vista Service Pack 1, Windows Vista Service Pack 2, Windows Vista x64 Edition, Windows Vista x64 Edition Service Pack 1, and Windows Vista x64 Edition Service Pack 2 Internet Explorer 8 in Windows Server 2008 for 32-bit Systems and Windows Server 2008 for 32-bit Systems Service Pack 2 Internet Explorer 8 in Windows Server 2008 for x64-based Systems and Windows Server 2008 for x64-based Systems Service Pack 2 Internet Explorer 8 in Windows 7 for 32-bit Systems Internet Explorer 8 in Windows 7 for x64-based Systems Internet Explorer 8 in Windows Server 2008 R2 for x64-based Systems Internet Explorer 8 in Windows Server 2008 R2 for Itanium-based Systems Non-Affected Software Internet Explorer 5.01 Service Pack 4 for Microsoft Windows 2000 Service Pack 4 Workarounds Microsoft has tested the following workarounds. Although these workarounds will not correct the underlying vulnerability, they help block known attack vectors. When a workaround reduces functionality, it is identified in the following section. Set Internet and Local intranet security zone settings to "High" to prompt before running ActiveX Controls and Active Scripting in these zones You can help protect against exploitation of this vulnerability by changing your settings for the Internet security zone to prompt before running ActiveX controls and Active Scripting. You can do this by setting your browser security to High. To raise the browsing security level in Internet Explorer, follow these steps: 1. On the Internet Explorer Tools menu, click Internet Options. 2. In the Internet Options dialog box, click the Security tab, and then click the Internet icon. 3. Under Security level for this zone, move the slider to High. This sets the security level for all Web sites you visit to High. Note: If no slider is visible, click Default Level, and then move the slider to High. Note: Setting the level to High may cause some Web sites to work incorrectly. If you have difficulty using a Web site after you change this setting, and you are sure the site is safe to use, you can add that site to your list of trusted sites. This will allow the site to work correctly even with the security setting set to High. Impact of workaround. There are side effects to prompting before running ActiveX Controls and Active Scripting. Many Web sites that are on the Internet or on an intranet use ActiveX or Active Scripting to provide additional functionality. For example, an online e-commerce site or banking site may use ActiveX Controls to provide menus, ordering forms, or even account statements. Prompting before running ActiveX Controls or Active Scripting is a global setting that affects all Internet and intranet sites. You will be prompted frequently when you enable this workaround. For each prompt, if you feel you trust the site that you are visiting, click Yes to run ActiveX Controls or Active Scripting. If you do not want to be prompted for all these sites, use the steps outlined in "Add sites that you trust to the Internet Explorer Trusted sites zone". Add sites that you trust to the Internet Explorer Trusted sites zone After you set Internet Explorer to require a prompt before it runs ActiveX controls and Active Scripting in the Internet zone and in the Local intranet zone, you can add sites that you trust to the Internet Explorer Trusted sites zone. This will allow you to continue to use trusted Web sites exactly as you do today, while helping to protect you from this attack on untrusted sites. We recommend that you add only sites that you trust to the Trusted sites zone. To do this, follow these steps: 1. In Internet Explorer, click Tools, click Internet Options, and then click the Security tab. 2. In the Select a Web content zone to specify its current security settings box, click Trusted Sites, and then click Sites. 3. If you want to add sites that do not require an encrypted channel, click to clear the Require server verification (https:) for all sites in this zone check box. 4. In the Add this Web site to the zone box, type the URL of a site that you trust, and then click Add. 5. Repeat these steps for each site that you want to add to the zone. 6. Click OK two times to accept the changes and return to Internet Explorer. Note: Add any sites that you trust not to take malicious action on your system. Two in particular that you may want to add are *.windowsupdate.microsoft.com and *.update.microsoft.com. These are the sites that will host the update, and it requires an ActiveX Control to install the update. Configure Internet Explorer to prompt before running Active Scripting or to disable Active Scripting in the Internet and Local intranet security zone You can help protect against exploitation of this vulnerability by changing your settings to prompt before running Active Scripting or to disable Active Scripting in the Internet and Local intranet security zone. To do this, follow these steps: 1. In Internet Explorer, click Internet Options on the Tools menu. 2. Click the Security tab. 3. Click Internet, and then click Custom Level. 4. Under Settings, in the Scripting section, under Active Scripting, click Prompt or Disable, and then click OK. 5. Click Local intranet, and then click Custom Level. 6. Under Settings, in the Scripting section, under Active Scripting, click Prompt or Disable, and then click OK. 7. Click OK two times to return to Internet Explorer. Note: Disabling Active Scripting in the Internet and Local intranet security zones may cause some Web sites to work incorrectly. If you have difficulty using a Web site after you change this setting, and you are sure the site is safe to use, you can add that site to your list of trusted sites. This will allow the site to work correctly. Impact of workaround. There are side effects to prompting before running Active Scripting. Many Web sites that are on the Internet or on an intranet use Active Scripting to provide additional functionality. For example, an online e-commerce site or banking site may use Active Scripting to provide menus, ordering forms, or even account statements. Prompting before running Active Scripting is a global setting that affects all Internet and intranet sites. You will be prompted frequently when you enable this workaround. For each prompt, if you feel you trust the site that you are visiting, click Yes to run Active Scripting. If you do not want to be prompted for all these sites, use the steps outlined in "Add sites that you trust to the Internet Explorer Trusted sites zone". Add sites that you trust to the Internet Explorer Trusted sites zone After you set Internet Explorer to require a prompt before it runs ActiveX controls and Active Scripting in the Internet zone and in the Local intranet zone, you can add sites that you trust to the Internet Explorer Trusted sites zone. This will allow you to continue to use trusted Web sites exactly as you do today, while helping to protect you from this attack on untrusted sites. We recommend that you add only sites that you trust to the Trusted sites zone. To do this, follow these steps: 1. In Internet Explorer, click Tools, click Internet Options, and then click the Security tab. 2. In the Select a Web content zone to specify its current security settings box, click Trusted Sites, and then click Sites. 3. If you want to add sites that do not require an encrypted channel, click to clear the Require server verification (https:) for all sites in this zone check box. 4. In the Add this Web site to the zone box, type the URL of a site that you trust, and then click Add. 5. Repeat these steps for each site that you want to add to the zone. 6. Click OK two times to accept the changes and return to Internet Explorer. Note: Add any sites that you trust not to take malicious action on your system. Two in particular that you may want to add are *.windowsupdate.microsoft.com and *.update.microsoft.com. These are the sites that will host the update, and it requires an ActiveX Control to install the update. Top of sectionTop of section Enable DEP for Internet Explorer 6 Service Pack 2 or Internet Explorer 7 This vulnerability is more difficult to exploit successfully if Data Execution Protection (DEP) is enabled for Internet Explorer. You can enable DEP for all versions of Internet Explorer that support DEP, using one of the following methods: Enable DEP for Internet Explorer 7 interactively Local Administrators can control DEP/NX by running Internet Explorer as an Administrator. To enable DEP, perform the following steps: 1. In Internet Explorer, click Tools, click Internet Options, and then click Advanced. 2. Click Enable memory protection to help mitigate online attacks. Enable DEP for Internet Explorer via automated Microsoft Fix It See Microsoft Knowledge Base Article 979352 to use the automated Microsoft Fix it solution to enable or disable this workaround. Impact of workaround Some browser extensions may not be compatible with DEP and may exit unexpectedly. If this occurs, you can disable the add-on, or revert the DEP setting using the Internet Control Panel. This is also accessible using the System Control panel. ====================================================================== ========================================================= 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 + =========================================================