__________________________________________________________ The U.S. Department of Energy Computer Incident Advisory Capability ___ __ __ _ ___ / | /_\ / \___ __|__ / \ \___ __________________________________________________________ INFORMATION BULLETIN Microsoft HTML Help ActiveX Control Vulnerabilities [Microsoft Security Bulletin MS02-055] October 3, 2002 18:00 GMT Number N-002 ______________________________________________________________________________ PROBLEM: An unchecked buffer vulnerability exists in the ActiveX control that provides the functionality for the HTML Help facility. Also found were two flaws allowing restrictions to be bypassed that handle the compiled HTML Help Files containing shortcuts enabling these files to take any desired system function. PLATFORM: Microsoft Windows 98 Microsoft Windows 98-Second Edition Microsoft Windows Millennium Edition Microsoft Windows NT 4.0 Microsoft Windows NT 4.0, Terminal Server Edition Microsoft Windows 2000 Microsoft Windows XP DAMAGE: At worst, an attacker could gain the same privileges as a user and run code of his/her choice at that privilege level. SOLUTION: Apply available patch. ______________________________________________________________________________ VULNERABILITY The risk is LOW. A user would need to visit a web page hosted ASSESSMENT: by the attacker that contains the malicious file, or the attacker would need to send the user an HTML e-mail that delivers a .chm file containing a shortcut which makes use of the flaws. ______________________________________________________________________________ LINKS: CIAC BULLETIN: http://www.ciac.org/ciac/bulletins/n-002.shtml ORIGINAL BULLETIN: http://www.microsoft.com/technet/treeview/default.asp?url= /technet/security/bulletin/MS02-055.asp PATCHES: - Windows 98 and Windows 98 SE: http://www.microsoft.com/windows98/downloads/contents/ WUCritical/q323255/default.asp - Windows Me: Only available via http://windowsupdate.microsoft.com/ - Windows NT 4.0: http://www.microsoft.com/Downloads/Release.asp?ReleaseID=43308 - Windows NT 4.0, Terminal Server Edition: http://www.microsoft.com/Downloads/Release.asp?ReleaseID=43308 - Windows 2000: http://www.microsoft.com/Downloads/Release.asp?ReleaseID=40213 - Windows XP Home Edition and Professional Edition: http://www.microsoft.com/Downloads/Release.asp?ReleaseID=41834 ______________________________________________________________________________ [***** Start Microsoft Security Bulletin MS02-055 *****] Microsoft Security Bulletin MS02-055 Unchecked Buffer in Windows Help Facility Could Enable Code Execution (Q323255) Originally posted: October 02, 2002 Summary Who should read this bulletin: Customers using Microsoft® Windows® 98, Windows Me, Windows NT® 4.0, Windows 2000, or Windows XP. Impact of vulnerability: Attacker could gain control over user’s system. Maximum Severity Rating: Critical Recommendation: Customers should install the patch immediately. Affected Software: Microsoft Windows 98 Microsoft Windows 98 Second Edition Microsoft Windows Millennium Edition Microsoft Windows NT 4.0 Microsoft Windows NT 4.0, Terminal Server Edition Microsoft Windows 2000 Microsoft Windows XP Technical details Technical description: The HTML Help facility in Windows includes an ActiveX control that provides much of its functionality. One of the functions exposed via the control contains an unchecked buffer, which could be exploited by a web page hosted on an attacker’s site or sent to a user as an HTML mail. An attacker who successfully exploited the vulnerability would be able to run code in the security context of the user, thereby gaining the same privileges as the user on the system. A second vulnerability exists because of flaws associated with the handling of compiled HTML Help (.chm) files that contain shortcuts. Because shortcuts allow HTML Help files to take any desired action on the system, only trusted HTML Help files should be allowed to use them. Two flaws allow this restriction to be bypassed. First, the HTML Help facility incorrectly determines the Security Zone in the case where a web page or HTML mail delivers a .chm file to the Temporary Internet Files folder and subsequently opens it. Instead of handling the .chm file in the correct zone – the one associated with the web page or HTML mail that delivered it – the HTML Help facility incorrectly handles it in the Local Computer Zone, thereby considering it trusted and allowing it to use shortcuts. This error is compounded by the fact that the HTML Help facility doesn’t consider what folder the content resides in. Were it to do so, it could recover from the first flaw, as content within the Temporary Internet Folder is clearly not trusted, regardless of the Security Zone it renders in. The attack scenario for this vulnerability would be complex, and involves using an HTML mail to deliver a .chm file that contains a shortcut, then making use of the flaws to open it and allow the shortcut to execute. The shortcut would be able to perform any action the user had privileges to perform on the system. Before deploying the patch, customers should familiarize themselves with the caveats discussed in the FAQ and in the Caveats section below. Mitigating factors: Buffer Overrun in HTML Help ActiveX Control: The HTML mail-based attack vector could not be exploited on systems where Outlook 98 or Outlook 2000 were used in conjunction with the Outlook Email Security Update, or Outlook Express 6 or Outlook 2002 were used in their default configurations. The vulnerability would convey only the user’s privileges on the system. Users whose accounts are configured to have few privileges on the system would be at less risk than ones who operate with administrative privileges. Code Execution via Compiled HTML Help File: The vulnerability could not be exploited via a web site. The vulnerability could only be exploited if the attacker were able to determine the exact location of the Temporary Internet Files folder. By design, this should not be possible, and Microsoft is unaware of any means for doing so which has not already been patched. The vulnerability would convey only the user’s privileges on the system. Users whose accounts are configured to have few privileges on the system would be at less risk than ones who operate with administrative privileges. Severity Rating: Buffer Overrun in HTML Help ActiveX Control: Internet Servers Intranet Servers Client Systems All affected products Moderate Moderate Critical Code Execution via Compiled HTML Help File: Internet Servers Intranet Servers Client Systems All affected products Low Low Moderate The above assessment is based on the types of systems affected by the vulnerability, their typical deployment patterns, and the effect that exploiting the vulnerability would have on them. Vulnerability identifier: Buffer Overrun in HTML Help ActiveX Control: CAN-2002-0693 Code Execution via Compiled HTML Help File: CAN-2002-0694 Tested Versions: Microsoft tested the HTML Help facilities in Windows 98, Windows 98 SE, Windows ME, Windows NT 4.0, Windows 2000 and Windows XP to assess whether they are affected by these vulnerabilities. Previous versions are no longer supported, and may or may not be affected by these vulnerabilities. Patch availability Download locations for this patch The patches for all Windows systems are available via Windows Update or can be manually applied via the following patches: Windows 98 and Windows 98 SE: http://www.microsoft.com/windows98/downloads/contents/WUCritical/q323255/ default.asp Windows Me: Only available via Windows Update. Windows NT 4.0: http://www.microsoft.com/Downloads/Release.asp?ReleaseID=43308 Windows NT 4.0, Terminal Server Edition: http://www.microsoft.com/Downloads/Release.asp?ReleaseID=43308 Windows 2000: http://www.microsoft.com/Downloads/Release.asp?ReleaseID=40213 Windows XP Home Edition and Professional Edition: http://www.microsoft.com/Downloads/Release.asp?ReleaseID=41834 Additional information about this patch Installation platforms: The Window 98 patch can be installed on systems running Windows 98 Gold. The Window 98SE patch can be installed on systems running Windows 98SE Gold. The Windows Me patch can be installed on systems running Windows Me Gold. The Windows NT 4.0 patch can be installed on systems running Service Pack 6a. The Windows NT 4.0 Terminal Server Edition patch can be installed on systems running Windows NT 4.0 Terminal Server Edition Service Pack 6. The Windows 2000 patch can be installed on systems running Windows 2000 Service Pack 1, Service Pack 2 or Service Pack 3. The patch for Windows XP can be installed on systems running Windows XP Gold or Service Pack 1. Inclusion in future service packs: The fix for this issue will be included in Windows 2000 Service Pack 4 and Windows XP Service Pack 2. Reboot needed: Yes Patch can be uninstalled: No Superseded patches: This patch supersedes the one delivered in Microsoft Security Bulletin MS00-037. Verifying patch installation: Windows 98, Windows 98SE and Window Me: To verify that the patch has been installed on the machine, use the Qfecheck.exe tool and confirm that the display includes the following information: UPD323255 Windows xx Q323255 Update where xx is “98” for Windows 98 or 98SE, or “Me” for Windows Me. To verify the individual files, consult the file manifest in Knowledge Base article Q323255. Windows NT 4.0: To verify that the patch has been installed on the machine, confirm that all files listed in the file manifest in Knowledge Base article Q323255 are present on the system. Windows NT 4.0 Terminal Server Edition: To verify that the patch has been installed on the machine, confirm that all files listed in the file manifest in Knowledge Base article Q323255 are present on the system. Windows 2000: To verify that the patch has been installed on the machine, confirm that the following registry key has been created on the machine: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Updates\Windows 2000\SP4\Q323255. To verify the individual files, use the date/time and version information provided in the following registry key: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Updates\Windows 2000\SP4\Q323255\Filelist. Windows XP: To verify that the patch has been installed, confirm that the following registry key has been created on the machine: HKLM\Software\Microsoft\Updates\Windows XP\SP2\Q323255. To verify the individual files, use the date/time and version information provided in the following registry key: HKLM\Software\Microsoft\Updates\Windows XP\SP2\Q323255\Filelist. Caveats: The patch requires that Internet Explorer 5.01, 5.5 or 6 be installed on the system. As discussed in the FAQ, the patch does not set the Kill Bit on the affected control. Localization: Localized versions of this patch are available at the locations discussed in “Patch Availability”. In particular, please note that the patch for Windows NT 4.0 and Windows NT 4.0 Terminal Server Edition can be installed on any language version, where there is a separately localized patch for other platforms. Obtaining other security patches: Patches for other security issues are available from the following locations: Security patches are available from the Microsoft Download Center, and can be most easily found by doing a keyword search for "security_patch". Patches for consumer platforms are available from the WindowsUpdate web site Other information: Acknowledgments Microsoft thanks David Litchfield of Next Generation Security Software Ltd. and Thor Larholm, Security Researcher, PivX Solutions, LLC (http://www.pivx.com) for reporting the Buffer Overrun in HTML Help ActiveX Control to us and working with us to protect customers. Support: Microsoft Knowledge Base article Q323255 discusses this issue and will be available approximately 24 hours after the release of this bulletin. Knowledge Base articles can be found on the Microsoft Online Support web site. Technical support is available from Microsoft Product Support Services. There is no charge for support calls associated with security patches. Security Resources: The Microsoft TechNet Security Web Site provides additional information about security in Microsoft products. Disclaimer: The information provided in the Microsoft Knowledge Base is provided "as is" without warranty of any kind. Microsoft disclaims all warranties, either express or implied, including the warranties of merchantability and fitness for a particular purpose. In no event shall Microsoft Corporation or its suppliers be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages, even if Microsoft Corporation or its suppliers have been advised of the possibility of such damages. Some states do not allow the exclusion or limitation of liability for consequential or incidental damages so the foregoing limitation may not apply. Revisions: V1.0 (October 02, 2002): Bulletin Created. [***** End Microsoft Security Bulletin MS02-055 *****] _______________________________________________________________________________ CIAC wishes to acknowledge the contributions of Microsoft Corporation for the information contained in this bulletin. _______________________________________________________________________________ CIAC, the Computer Incident Advisory Capability, is the computer security incident response team for the U.S. Department of Energy (DOE) and the emergency backup response team for the National Institutes of Health (NIH). CIAC is located at the Lawrence Livermore National Laboratory in Livermore, California. CIAC is also a founding member of FIRST, the Forum of Incident Response and Security Teams, a global organization established to foster cooperation and coordination among computer security teams worldwide. CIAC services are available to DOE, DOE contractors, and the NIH. CIAC can be contacted at: Voice: +1 925-422-8193 (7x24) FAX: +1 925-423-8002 STU-III: +1 925-423-2604 E-mail: ciac@ciac.org Previous CIAC notices, anti-virus software, and other information are available from the CIAC Computer Security Archive. World Wide Web: http://www.ciac.org/ Anonymous FTP: ftp.ciac.org PLEASE NOTE: Many users outside of the DOE, ESnet, and NIH computing communities receive CIAC bulletins. If you are not part of these communities, please contact your agency's response team to report incidents. Your agency's team will coordinate with CIAC. The Forum of Incident Response and Security Teams (FIRST) is a world-wide organization. A list of FIRST member organizations and their constituencies can be obtained via WWW at http://www.first.org/. This document was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor the University of California nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial products, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation or favoring by the United States Government or the University of California. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or the University of California, and shall not be used for advertising or product endorsement purposes. 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