Microsoft Windows compiled HTML Help (.chm) files could be used to execute code

win-chm-code-execution (10254) The risk level is classified as MediumMedium Risk


Microsoft Windows could allow a remote attacker to execute arbitrary code on a victim's system, caused by a vulnerability regarding improper permissions on compiled HTML Help (.chm) files. A remote attacker could create a malicious .chm file containing a shortcut that could link to a malicious executable. If the attacker could create a malicious Web page that calls this file from the Temporary Internet Folder (TIF) directory after it has been saved by the victim, the attacker could then cause malicious code to be executed in the victim's system within the victim's Local Computer Zone.


Gain Access


Apply the appropriate patch for your system, as listed in Microsoft Security Bulletin MS02-055. See References.


  • CIAC Information Bulletin N-002: Microsoft HTML Help ActiveX Control Vulnerabilities.
  • Microsoft Security Bulletin MS02-055: Unchecked Buffer in Windows Help Facility Could Enable Code Execution (Q323255).
  • CVE-2002-0694: The HTML Help facility in Microsoft Windows 98, 98 Second Edition, Millennium Edition, NT 4.0, NT 4.0 Terminal Server Edition, Windows 2000, and Windows XP uses the Local Computer Security Zone when opening .chm files from the Temporary Internet Files folder, which allows remote attackers to execute arbitrary code via HTML mail that references or inserts a malicious .chm file containing shortcuts that can be executed, aka Code Execution via Compiled HTML Help File.
  • OSVDB ID: 867: Microsoft Windows Compiled HTML Help (.chm) Arbitrary Command Execution

Platforms Affected:

  • Microsoft Windows 2000
  • Microsoft Windows 98
  • Microsoft Windows 98SE
  • Microsoft Windows Me
  • Microsoft Windows NT 4.0
  • Microsoft Windows NT 4.0 Terminal Server
  • Microsoft Windows XP


Oct 02, 2002

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