This vulnerability would lead an attacker to execute arbitrary code due to memory corruption caused by a recursive CSS call in IE. The workaround issued by Microsoft is based on a control check that rejects recursive calls for style sheets with the same URLs.
Microsoft recommends users to install the new workaround until a security update is available. Note, that you must have the latest security updates in place before installing the fix. Since the fix is an msi package I suggest that you visit and follow MS release notes for a complete and successful installation.