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TUCoPS :: Windows :: n-002.txt

Microsoft HTML Help ActiveX Control Vulnerabilities (CIAC N-002)




             __________________________________________________________

                       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
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can be contacted at:
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PLEASE NOTE: Many users outside of the DOE, ESnet, and NIH computing
communities receive CIAC bulletins.  If you are not part of these
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incidents. Your agency's team will coordinate with CIAC. The Forum of
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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
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