Microsoft Internet Explorer is prone to a memory-corruption vulnerability that is related to the instantiation of COM objects. This issue results from a design error. The vulnerability arises because of the way Internet Explorer tries to instantiate certain COM objects as ActiveX controls, resulting in arbitrary code execution. The affected objects are not intended to be instantiated through Internet Explorer. This BID is related to the issues described in BID 14511 (Microsoft Internet Explorer COM Object Instantiation Buffer Overflow Vulnerability) and BID 15061 Microsoft Internet Explorer COM Object Instantiation Variant Vulnerability). However, this issue affects a different set of COM objects that were not addressed in the previous BIDs.
Run all software as a nonprivileged user with minimal access rights.
Ensure that all non-administrative tasks, such as browsing the web and reading email, are performed as an unprivileged user with minimal access rights.
Do not follow links provided by unknown or untrusted sources.
Users should never visit sites of questionable integrity or follow links provided by unfamiliar or untrusted sources.
Set web browser security to disable the execution of script code or active content.
Disabling scripting and active content in the Internet Zone may limit exposure to this and other vulnerabilities.
Implement multiple redundant layers of security.
As an added precaution, deploy memory-protection schemes (such as non-executable stack/heap configuration and randomly mapped memory segments). This may complicate exploitation of memory-corruption vulnerabilities.
Microsoft has released a cumulative security update to address this issue. Reportedly, the fixes provided in MS06-013 may cause unintended breakage with certain ActiveX controls. Symantec has not confirmed this. Before deploying this patch in production environments, users should thoroughly test the patch to ensure that it doesn't interfere with other software.