Microsoft Windows compiled Help (.CHM) integer overflow

win-htmlhelp-code-execution (20821) The risk level is classified as HighHigh Risk


Microsoft Windows could allow a remote attacker to execute arbitrary code on the system, caused by an integer overflow that can occur when handling specially-crafted compiled Help (.CHM) files. A remote attacker could exploit this vulnerability using a malicious Web page to trigger a heap-based buffer overflow, which would allow the attacker to execute arbitrary code and possibly gain complete control over a victim's system, if the attacker could persuade the victim to visit the malicious Web page.


Gain Access


Apply the appropriate patch for your system, as listed in Microsoft Security Bulletin MS05-026. See References.


  • Microsoft Security Bulletin MS05-026: Vulnerability in HTML Help Could Allow Remote Code Execution (896358).
  • VulnWatch Mailing List, Tue Jun 14 2005 - 18:57:58 CDT: eEye Advisory - EEYEB-20050316 - HTML Help File Parsing Buffer Overflow.
  • BID-13953: Microsoft Windows HTML Help Remote Code Execution Vulnerability
  • CVE-2005-1208: Integer overflow in Microsoft Windows 98, 2000, XP SP2 and earlier, and Server 2003 SP1 and earlier allows remote attackers to execute arbitrary code via a crafted compiled Help (.CHM) file with a large size field that triggers a heap-based buffer overflow, as demonstrated using a ms-its: URL in Internet Explorer.
  • SA15683: Microsoft Windows HTML Help Input Validation Vulnerability
  • US-CERT VU#851869: Microsoft HTML Help vulnerable to integer overflow

Platforms Affected:

  • Microsoft Windows 2000 SP3
  • Microsoft Windows 2000 SP4
  • Microsoft Windows 2003 Server SP1 Itanium
  • Microsoft Windows 2003 Server SP1
  • Microsoft Windows 2003 Server Itanium
  • Microsoft Windows 2003 Server x64
  • Microsoft Windows 2003 Server
  • Microsoft Windows 98
  • Microsoft Windows 98SE
  • Microsoft Windows Me
  • Microsoft Windows XP 2003 x64 Itanium
  • Microsoft Windows XP SP1 x64 Itanium
  • Microsoft Windows XP SP1
  • Microsoft Windows XP x64 Professional
  • Microsoft Windows XP SP2


Jun 14, 2005

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