Microsoft Internet Explorer DHTML Object Race Condition Memory Corruption Vulnerability



Date Discovered

April 12, 2005


A vulnerability in Microsoft Internet Explorer may allow remote attackers to execute arbitrary code in the context of users visiting malicious Web sites. This issue presents itself the affected application attempts to process certain script objects, a race condition may lead to the execution of attacker-supplied code.

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 5.5
  • Microsoft Internet Explorer 5.5 SP1
  • Microsoft Internet Explorer 5.5 SP2
  • Microsoft Internet Explorer 6.0
  • Microsoft Internet Explorer 6.0 SP1
  • Microsoft Internet Explorer 6.0 SP2 do not use


Run all software as a nonprivileged user with minimal access rights.
Non-administrative software should be run as non-administrative users with the least privileges required. This will limit the potential damage that successful exploitation may achieve.

Set web browser security to disable the execution of script code or active content.
Exploitation of this vulnerability requires the execution of malicious script code in the affected Web browser. Disabling script code and active content support within the affected browser should prevent successful exploitation of this issue. It should be noted that this mitigation tactic might adversely affect legitimate Web sites that rely on the execution of browser based script code.

Do not accept communications that originate from unknown or untrusted sources.
Users should not follow suspicious links, or open email that originates from unknown or untrusted sources.

Review and adjust according to policy any default configuration settings.
Users should disable HTML rendering of email messages in Outlook and Outlook Express, as this will limit the possibility of successful exploitation.

Microsoft has released updates to address this vulnerability on supported platforms. Internet Explorer 6 for Windows Server 2003 SP 1 including 64-Bit Edition is not affected by this issue. Windows XP Professional x64 Edition is also not affected. Microsoft has released fixes for Windows 98, Windows 98 Second Edition, and Windows Millennium Edition. These updates are available from the Windows Update Web site: Localized Slovenian and Slovakian fixes are available for Windows 98, Windows 98 Second Edition, and Windows Millennium Edition as well. Please see the referenced Microsoft bulletin for more information.



Berend-Jan Wever is credited for the discovery of this vulnerability.

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