Microsoft Internet Explorer HTML Layout and Positioning Remote Code Execution Vulnerability



Date Discovered

August 8, 2006


Microsoft Internet Explorer is prone to a remote code-execution vulnerability. This vulnerability is related to how the browser renders HTML with certain layout and positioning combinations. An attacker could exploit this issue to execute arbitrary code in the context of the user visiting a malicious web page. This issue affects Internet Explorer on Windows 2000, Windows XP, and Windows Server 2003.

Technologies Affected

  • 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 SP4
  • Microsoft Internet Explorer 6.0
  • Microsoft Internet Explorer 6.0 SP1
  • Nortel Networks CallPilot 1002rp
  • Nortel Networks CallPilot 200i
  • Nortel Networks CallPilot 201i
  • Nortel Networks CallPilot 702t
  • Nortel Networks CallPilot 703t
  • Nortel Networks Centrex IP Client Manager
  • Nortel Networks Centrex IP Element Manager
  • Nortel Networks Contact Center - Agent Desktop Display
  • Nortel Networks Contact Center - Symposium Agent


Run all software as a nonprivileged user with minimal access rights.
To reduce the impact of latent vulnerabilities, always run non-administrative software as an unprivileged user with minimal access rights.

Do not follow links provided by unknown or untrusted sources.
Attackers could exploit this vulnerability by enticing a user to visit a malicious website. Do not follow links provided by sources of questionable integrity.

Implement multiple redundant layers of security.
Since this issue may be leveraged to execute code, we recommend memory-protection schemes, such as non-executable stack/heap configurations and randomly mapped memory segments. This tactic may complicate exploits of memory-corruption vulnerabilities.

Microsoft has released a security bulletin to address this issue. Please see the referenced security bulletin for details. MS06-042 has been reissued to address a vulnerability introduced with the previous fixes. Please see BID 19667 (Microsoft Internet Explorer HTTP 1.1 and Compression Long URI Buffer Overflow Vulnerability) for further information on this issue. Microsoft Security Bulletin MS06-042 has been updated to address a flaw in Mshtml.dll that was introduced in the previous fixes. Please see the referenced advisory for more information.



Discovery is credited to Sam Thomas.

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