In February, Microsoft awarded $100,000 to Yu Yang (@Tombkeeper) for reporting a new mitigation bypass technique as part of Microsoft’s Bounty Program. Yu later demonstrated his research at CanSecWest in March. In his slides, he mentioned that a "god mode" of Internet Explorer could be turned on by a one byte overwrite. However, he had to heavily redact this information due to an agreement between himself and Microsoft.
After his slides were released, researchers began working to determine what the missing parts were. And before long, Yuki Chen (@guhe120), a Chinese researcher, posted his answer. Although the code was removed soon after posting, a copy was still maintained and used by Metasploit. Following this code, another researcher posted his VB script version using more advanced techniques. Yu Yang then pasted his shellcode that used similar methods to run arbitrary code, showing that the method Yuki Chen used is exactly the one that won Yu the $100,000 award.
The main idea of new exploitation technique is to alter a flag that is used to control the security setting of an ActiveX object. If an attacker could modify it, then any script can be run, such as downloading and executing a PE file, without any notification or alert. Further details were discussed in depth last month on Rapid7’s blog. The most interesting aspect of this method is that it could bypass all existing mitigation techniques including DEP/ASLR/EMET, and it also defeats some academic methods such as Control Flow Integrity (CFI). So this raises another question: If there are no mitigation functions, do we have any other ways to defend against attacks similar to this?
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