Software Engineering Institute

Microsoft XML Core Services (MSXML) allow developers who use applications such as JScript, Visual Basic Scripting Edition (VBScript), and Microsoft Visual Studio to create XML-based applications. MSXML includes the XMLHTTP ActiveX control, which allows web pages to transmit or receive XML data via HTTP operations. MSXML 4.0 does not come with Windows XP by default, but is available as a separate download and is also bundled with many applications.

The XMLHTTP 4.0 ActiveX control contains an unspecified memory corruption vulnerability. When certain methods of the XMLHTTP ActiveX control are called with invalid parameters, process memory is corrupted in an exploitable manner.

Note that this vulnerability is being actively exploited. Exploit code for this vulnerability is publicly available.

By convincing a user to view a specially crafted HTML document (e.g., a web page or an HTML email message or attachment), an attacker may be able to execute arbitrary code with the privileges of the user. The attacker could also cause Internet Explorer (or the program using the WebBrowser control) to crash.

Apply an Update

Microsoft has released updates in Microsoft Security Bulletin MS06-071 to address this issue.

Microsoft Security Bulletin MS06-071 lists several workarounds, including:

Disable the XMLHTTP 4.0 object in Internet Explorer

The XMLHTTP 4.0 ActiveX control can be disabled in Internet Explorer by setting the kill bit for the following CLSID:

{88d969c5-f192-11d4-a65f-0040963251e5}
More information about how to set the kill bit is available in Microsoft Support Document 240797. Alternatively, the following text can be saved as a .REG file and imported to set the kill bit for this control:

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\ActiveX Compatibility\{88d969c5-f192-11d4-a65f-0040963251e5}]
"Compatibility Flags"=dword:00000400
Disable ActiveX

Disabling ActiveX controls in the Internet Zone (or any zone used by an attacker) appears to prevent exploitation of this and other ActiveX vulnerabilities. Instructions for disabling ActiveX in the Internet Zone can be found in the "Securing Your Web Browser" document. 

Note: Please see Microsoft Security Bulletin MS06-071 for further details.