Public Vulnerability Reports

Microsoft Internet Explorer HTML Tag Long File Name Extension Stack Buffer Overflow Vulnerability

09.12.08

BACKGROUND

Internet Explorer is a graphical web browser developed by Microsoft Corp. that has been included with Microsoft Windows since 1995. For more information about Internet Explorer, please the visit following website: http://www.microsoft.com/ie/

DESCRIPTION

Remote exploitation of a stack buffer overflow vulnerability while handling specific HTML tags in Microsoft Corp.'s Internet Explorer web browser allows attackers to execute arbitrary code within the context of the affected user.

On Internet Explorer 5.01 a function return address can be overwritten with attacker controlled data which results in an exploitable condition. However on Internet Explorer 6 the vulnerability will only overflow one byte. For Internet Explorer 6 on Windows 2000 platform, the overflowed byte is in a local variable, and overwriting it doesn't affect program execution at all. For Internet Explorer 6 on Windows XP SP2, the overflowed byte is in the stack cookie, which causes Internet Explorer to terminate and only results in a denial of service.

ANALYSIS

Successful exploitation of this vulnerability would allow an attacker to execute arbitrary code in the context of the user running the Internet Explorer. However, the execution of arbitrary code is only possible on Windows 2000 SP4 running Internet Explorer 5.01.

Exploitation would require an attacker to persuade a user to visit a malicious website using Internet Explorer.

DETECTION

As of September 2008, iDefense confirms that Internet Explorer 5.01 on Windows 2000 SP4, is vulnerable. It also causes denial of service for Internet Explorer 6 on Windows XP SP2. Internet Explorer 7 is not affected.

WORKAROUND

iDefense is not aware of any effective workaround for this issue. Customers are encouraged to upgrade Internet Explorer to version 6 or above.

VENDOR RESPONSE

Microsoft has released a patch which addresses this issue. For more information, consult their advisory at the following URL.

http://www.microsoft.com/technet/security/bulletin/ms08-073.mspx

Microsoft recommends that customers apply the update immediately.

CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the name CVE-2008-4261 to this issue. This is a candidate for inclusion in the CVE list (http://cve.mitre.org/), which standardizes names for security problems.

DISCLOSURE TIMELINE

08/26/2008 Initial Vendor Notification
08/26/2008 Initial Vendor Reply
09/24/2008 Additional Vendor Feedback
12/02/2008 Additional Vendor Feedback
12/09/2008 Coordinated Public Disclosure

CREDIT

This vulnerability was discovered by Jun Mao of iDefense Labs.

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LEGAL NOTICES

Copyright © 2008 Verisign, Inc.

Permission is granted for the redistribution of this alert electronically. It may not be edited in any way without the express written consent of iDefense. If you wish to reprint the whole or any part of this alert in any other medium other than electronically, please e-mail customer service for permission.

Disclaimer: The information in the advisory is believed to be accurate at the time of publishing based on currently available information. Use of the information constitutes acceptance for use in an AS IS condition. There are no warranties with regard to this information. Neither the author nor the publisher accepts any liability for any direct, indirect, or consequential loss or damage arising from use of, or reliance on, this information.