Microsoft Internet Explorer COM Object Instantiation Buffer Overflow Vulnerability



Date Discovered

August 9, 2005


Microsoft Internet Explorer is prone to a buffer-overflow vulnerability that is exposed when certain COM objects are instantiated as ActiveX controls. A malicious webpage could pass content to these objects to trigger memory corruption. Successful exploits could let remote attackers execute arbitrary code in the context of the currently logged-in user.

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.
All nonadministrative tasks, such as browsing the web and reading email, should be performed as an unprivileged user with minimal access rights.

Do not follow links provided by unknown or untrusted sources.
To reduce the likelihood of successful exploits, 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.
To limit exposure to this and other vulnerabilities, disable scripting and active content in the Internet Zone.

Implement multiple redundant layers of security.
Memory-protection schemes such as nonexecutable stack/heap configuration and randomly mapped memory segments may complicate exploits of memory-corruption vulnerabilities.

Microsoft has released fixes to address supported versions of the software. Fixes for Internet Explorer on Windows 98/98SE/ME may be obtained through Windows Update. Microsoft has updated the security bulletin for this issue to reflect the availability of updated fixes. This is due to an issue with Systems Management Server (SMS) and the original fixes. Users who updated using Automatic Update, Windows Update, Microsoft Update, and Windows Server Update Services (WSUS) do not need to reapply the fixes.



Discovery is credited to Bernhard Mueller and Martin Eiszner of SEC Consult and the NSFOCUS Security Team.

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