N-114: Buffer Overrun in Microsoft HTML Converter Could Allow Code Execution

[***** Start Microsoft Security Bulletin MS03-023 *****]

Microsoft Security Bulletin MS03-023 

Buffer Overrun In HTML Converter Could Allow Code Execution (823559)
Originally posted: July 9, 2003

Summary
Who should read this bulletin: Users running Microsoft ® Windows ® 

Impact of vulnerability: Run code of attacker’s choice 

Maximum Severity Rating: Critical 

Recommendation: Systems administrators should apply the patch 
immediately 

Affected Software: 

Microsoft Windows 98 
Microsoft Windows 98 Second Edition 
Microsoft Windows Me 
Microsoft Windows NT 4.0 Server 
Microsoft Windows NT 4.0 Terminal Server Edition 
Microsoft Windows 2000 
Microsoft Windows XP 
Microsoft Windows Server 2003 

 Technical details

Technical description: 

All versions of Microsoft Windows contain support for file conversion 
within the operating system. This functionality allows users of Microsoft 
Windows to convert file formats from one to another. In particular, 
Microsoft Windows contains support for HTML conversion within the operating 
system. This functionality allows users to view, import, or save files as 
HTML. 

There is a flaw in the way the HTML converter for Microsoft Windows handles 
a conversion request during a cut-and-paste operation. This flaw causes a 
security vulnerability to exist. A specially crafted request to the HTML 
converter could cause the converter to fail in such a way that it could 
execute code in the context of the currently logged-in user. Because this 
functionality is used by Internet Explorer, an attacker could craft a 
specially formed Web page or HTML e-mail that would cause the HTML 
converter to run arbitrary code on a user's system. A user visiting an 
attacker’s Web site could allow the attacker to exploit the vulnerability 
without any other user action. 

To exploit this vulnerability, the attacker would have to create a 
specially-formed HTML e-mail and send it to the user. Alternatively, an 
attacker would have to host a malicious Web site that contains a Web page 
designed to exploit this vulnerability. The attacker would then have to 
persuade a user to visit that site. 

Mitigating factors: 

By default, Internet Explorer on Windows Server 2003 runs in Enhanced 
Security Configuration. This default configuration of Internet Explorer 
blocks automatic exploitation of this attack. If Internet Explorer Enhanced 
Security Configuration has been disabled, the protections put in place that 
prevent this vulnerability from being automatically exploited would be removed. 

In the Web-based attack scenario, the attacker would have to host a Web site 
that contained a Web page used to exploit this vulnerability. An attacker 
would have no way to force users to visit a malicious Web site outside the HTML
e-mail vector. Instead, the attacker would need to lure them there, typically 
by getting them to click a link that would take them to the attacker's site. 

Exploiting the vulnerability would allow the attacker only the same privileges 
as the user. 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: 	Windows 98 				Critical 
			Windows 98 Second Edition 		Critical 
			Windows Me 				Critical 
			Windows NT 4.0 Server 			Critical 
			Windows NT 4.0 Terminal Server Edition 	Critical 
			Windows 2000 				Critical 
			Windows XP 				Critical 
			Windows Server 2003 			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: CAN-2003-0469 

Tested Versions:
Microsoft tested Windows 98, Windows 98 Second Edition, Windows Me, Windows NT 4.0 
Server, Windows NT 4.0 Terminal Services Edition, Windows 2000, Windows XP and 
Windows Server 2003 to assess whether they are affected by this vulnerability. 
Previous versions are no longer supported, and may or may not be affected by these 
vulnerabilities.

Patch availability

Download locations for this patch 

Windows NT 4.0 Server
Windows NT 4.0 Terminal Server Edition
Windows 2000
Windows XP 32 bit Edition
Windows XP 64 bit Edition
Windows Server 2003 32 bit Edition
Windows Server 2003 64 bit Edition

 Additional information about this patch

Installation platforms: 

The Window 98 patch can be installed on systems running Windows 98 Gold. 
The Window 98 Second Edition 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 3, or Service Pack 4. 
The patch for Windows XP can be installed on systems running Windows XP Gold or 
Service Pack 1. 
The patch for Windows Server 2003 can be installed on systems running Windows 
Server 2003 Gold. 

Inclusion in future service packs:
The fix for this issue will be included in Windows 2000 Service Pack 5, Windows 
XP Service Pack 2, and Windows Server 2003 Service Pack 1. 

Reboot needed: No. 

Patch can be uninstalled: Yes. 

Superseded patches: None. 

Verifying patch installation: 

Windows 98, Windows 98 Second Edition, Windows Me:
To verify that the patch has been installed on the machine consult the file 
manifest in Knowledge Base article 823559. 

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 823559 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 823559 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\SP5\KB823559.

To verify the individual files, use the date/time and version information 
provided in the file manifest in Knowledge Base article 823559 are present on 
the system. 

Windows XP:
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 XP\SP2\KB823559.

To verify the individual files, use the date/time and version information 
provided in the file manifest in Knowledge Base article 823559 are present on 
the system. 

Windows Server 2003: 
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\Window Server 2003\SP1\KB823559. 

To verify the individual files, use the date/time and version information 
provided in the file manifest in Knowledge Base article 823559 are present on 
the system. 

Caveats:
None 

Localization:
Localized versions of this patch are available at the locations discussed in 
“Patch Availability”. 

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: 

Support: 

Microsoft Knowledge Base article 823559 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 (July 9, 2003): Bulletin Created. 

[***** End Microsoft Security Bulletin MS03-023 *****]

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