Software Engineering Institute

Component Object Model, or COM objects, are used to enable interprocess communication and dynamic object creation within Microsoft Windows. Microsoft Internet Explorer contains a vulnerability that could be exploited when it attempts to load specially crafted web sites that instantiate specific COM objects contained in Msb1fren.dll, Htmlmm.ocx, or Blnmgrps.dll. According to Microsoft Security Bulletin MS07-016

When Internet Explorer tries to instantiate certain COM objects as ActiveX controls, the COM objects may corrupt the system state in such a way that an attacker could execute arbitrary code.

Note that this vulnerability does not affect Windows Internet Explorer 7 in Windows Vista.

A remote, unauthenticated attacker may be able to execute arbitrary code or cause a denial-of-service condition.

Update
Microsoft has released an update to address this issue. See Microsoft Security Bulletin MS07-016 for more details.

Disable ActiveX

Disabling ActiveX controls in the Internet Zone (or any zone used by an attacker) appears to prevent exploitation of this vulnerability. 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.