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  3. Microsoft Internet Explorer Double Byte Character Memory Corruption Vulnerability

Microsoft Internet Explorer Double Byte Character Memory Corruption Vulnerability

Risk

High

Date Discovered

April 11, 2006

Description

Microsoft Internet Explorer is prone to a memory-corruption vulnerability. This is related to an error in how double-byte character set (DBCS) characters are handled in Internationalized Domain Names (IDN) included in URLS from rendered HTML content. An attacker could exploit this issue via a malicious web page to execute arbitrary code in the context of the currently logged-in user. The issue could also be exploited through HTML email/newsgroup postings, or other applications that employ the affected component. Microsoft has stated that this issue does not apply to Internet Explorer 6.0 on Windows Server 2003 SP1.

Technologies Affected

  • Microsoft Internet Explorer 5.0.1
  • Microsoft Internet Explorer 5.0.1 SP1
  • Microsoft Internet Explorer 5.0.1 SP2
  • Microsoft Internet Explorer 5.0.1 SP3
  • Microsoft Internet Explorer 5.0.1 SP4
  • Microsoft Internet Explorer 5.0.1 for Windows 2000
  • Microsoft Internet Explorer 5.0.1 for Windows 95
  • Microsoft Internet Explorer 5.0.1 for Windows 98
  • Microsoft Internet Explorer 5.0.1 for Windows NT 4.0
  • Microsoft Internet Explorer 6.0
  • Microsoft Internet Explorer 6.0 SP1
  • Microsoft Internet Explorer 6.0 SP2 - do not use

Recommendations

Run all software as a nonprivileged user with minimal access rights.

Ensure that all non-administrative tasks, such as browsing the web and reading email, are performed as an unprivileged user with minimal access rights.

Do not follow links provided by unknown or untrusted sources.

Users should never visit sites of questionable integrity or follow links provided by unfamiliar or untrusted sources.

Set web browser security to disable the execution of script code or active content.

Disabling scripting and active content in the Internet Zone may limit exposure to this and other vulnerabilities.

Implement multiple redundant layers of security.

As an added precaution, deploy memory-protection schemes (such as non-executable stack/heap configuration and randomly mapped memory segments). This may complicate exploitation of memory-corruption vulnerabilities.

Disable any services that are not needed.

Disable support for HTML email in the email client. This may limit email-based attack vectors for this and other vulnerabilities.
Microsoft has released a cumulative security update to address this issue. Updates for Internet Explorer on Windows 98/98SE/ME may be obtained through Windows Update. Reportedly, the fixes provided in MS06-013 may cause unintended breakage with certain ActiveX controls. Symantec has not confirmed this. Before deploying this patch in production environments, users should thoroughly test the patch to ensure that it doesn't interfere with other software.

Credits

Sowhat is credited with the discovery of this vulnerability.
Copyright © Symantec Corporation.
Permission to redistribute this alert electronically is granted as long as it is not edited in any way unless authorized by Symantec Security Response. Reprinting the whole or part of this alert in any medium other than electronically requires permission from secure@symantec.com.

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.
Symantec, Symantec products, Symantec Security Response, and secure@symantec.com are registered trademarks of Symantec Corp. and/or affiliated companies in the United States and other countries. All other registered and unregistered trademarks represented in this document are the sole property of their respective companies/owners.

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