Software Engineering Institute

Microsoft COM

Microsoft COM is a technology that allows programmers to create reusable software components that can be incorporated into applications to extend their functionality. Microsoft COM includes COM+, Distributed COM (DCOM), and ActiveX Controls.

ActiveX controls

ActiveX controls are COM objects that are designed to be used in Internet Explorer. A web page can make use of an ActiveX control by referencing its Class Identifier (CLSID) in an HTML OBJECT tag.

DirectX Transform

DirectX Transform is a DirectX API that is used to apply visual effects to images. Internet Explorer filters use DirectX Transform ActiveX controls.

The problem

The DXImageTransform.Microsoft.Light filter fails to validate input to several of its methods. A specially crafted call to one such method can cause Internet Explorer to crash in a way that can be exploited to execute arbitrary code on a vulnerable system.

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 IE (or the program using the WebBrowser control) to crash.

Apply an update

This issue is addressed in Microsoft Security Bulletin MS06-021.

Disable the DXImageTransform.Microsoft.Light filter

The DXImageTransform.Microsoft.Light filter can be disabled by setting the kill bit for the following CLSID:

{F9EFBEC2-4302-11D2-952A-00C04FA34F05}
More information about how to set the kill bit is available in Microsoft Support Document 240797.

Disable ActiveX

Disabling ActiveX controls in the Internet Zone (or any zone used by an attacker) appears to prevent exploitation of this vulnerability. Internet Explorer will not use the vulnerable DirectX Transform filters when ActiveX controls are disabled. Instructions for disabling ActiveX in the Internet Zone can be found in the document Securing Your Web Browser and the Malicious Web Scripts FAQ.

Note that disabling ActiveX controls in the Internet Zone will reduce the functionality of some web sites.