Buffer Overflow in IE/Outlook HTML Help

["NGS Insight Security Research" <nisr () nextgenss com>]

NGSSoftware Insight Security Research Advisory

Name: Windows Help System Buffer Overflow
Systems: Windows XP,2000,NT,ME and 98
Severity: High Risk
Category: Buffer Overflow Vulnerability
Vendor URL: http://www.microsoft.com/
Author: David Litchfield (david () ngssoftware com)
Advisory URL: http://www.ngssoftware.com/advisories/ms-winhlp.txt
Date: 2nd October 2002
Advisory number: #NISR02102002


Introduction
************
The Windows Help system includes an ActiveX control known as the HTML Help
Control, hhctrl.ocx. The "Alink" function of this control is vulnerable to a
buffer overflow that can be exploited to gain control of the user's machine.

Details
*******
By providing an overly long parameter to the vulnerable function an internal
buffer is overflowed and program control structures can be overwritten
allowing an attacker to remotely gain control of their victims PC. This
could be done by enticing the victim to a website that contained a webpage
that exploits the vulnerability or by sending the victim an HTML mail. When
opened in Outlook the overflow will be triggered.

Fix Information
***************
Microsoft have produced a patch which is available from their web site.
More details are available from

http://www.microsoft.com/technet/treeview/?url=/technet/security/bulletin/MS
02-055.asp