Today, Microsoft released a critical security advisory warning customers of a serious new zero day vulnerability that affects Windows, Office, and Lync.
In a nutshell, the vulnerability has to do with how certain versions of Windows, Office, and Lync handle specially crafted TIFF images. If an attacker can trick you into viewing a malicious image, including ones embedded in Office documents, he can exploit this flaw to execute code on your computer, with your privileges. If you have local administrative permissions, as most Windows users do, they attacker gains complete control of your computer.
McAfee researchers first discovered this flaw being exploited in the wild, and they share some interesting details about the issue on their blog (Microsoft also shares some extra technical detail here). While the flaw lies in Microsoft’s image handling components (GDI+), the public attack actually arrives as a malicious Word document with an embedded TIFF, which the attackers send via email. Microsoft claims attackers are only exploiting the flaw in limited, targeted cases.
Since they just learned about the flaw recently, Microsoft hasn’t had time to patch it yet. However, they have released a FixIt which mitigates the issue. FixIts are not considered full patches, but they can protect you until Microsoft releases their final update. If you use any of the affected versions of Windows, Office, or Lync, I highly recommend you apply the FixIt as soon as you can. Microsoft does also offers a few other workarounds, such as disabling the TIFF codec, or using the EMET tool (something I suggest you do in general), but I think the FixIt is the quickest and most reliable solution.
I’ll continue to follow this issue as it evolves, and will post here as soon as Microsoft releases a patch. — Corey Nachreiner, CISSP (@SecAdept)
Alexander Kushnarev (Rainbow Security) says
Anatomy of this exploit is very interesting, and looks like it’s crafted not by a single person. Besides, authors thought “out of box”:
– Exploit performs a large memory heap-spray with ActiveX controls, not with Adobe Flash Player;
– Hardcoded ROP (return-oriented programming) gadgets (pieces of opcode) are used;
– Exploit can successfully bypass DEP and address address randomization, as a result of two points above;
– And of course (kind of advanced “stack smashing”), careful substitution of instruction pointer (EIP) moves the CPU to execution of the most desired by attacker part of exploit.
Another example of hi-tech in exploitation…
Corey Nachreiner says
I always appreciate you comments and deep understanding of how memory corruption exploits work (though I don’t always fine the time to reply… sooo busy).
I totally agree… this case (and the recent ActiveX control 0day) seems like it comes from fairly advanced attackers that know their way around an assembler, and how to evade some of the memory security features in Windows. By the way, you may have seen these, but I thought they were interesting reads:
I do like that Microsoft is focusing on more types of memory protection (DEP and ASLR help, but attackers have already found ways around). Windows 8 and 8.x seem to be stronger, but ppl will find bugs… You surely know about it, but I wish more regular Windows administrators would use EMET more often, it can often help quite a bit!
Hope you are well… Would love to visit Russia one day!
Alexander Kushnarev says
Thanks for links and kind words, Corey.
I’m a technical person, hungry for knowledges, and love pre-sales area 🙂
“Would love to visit Russia one day!”
If you will visit Russia – hope we can meet in person, and have a discussion about technologies and features of pre-sales activities. I like discussions with IT/infosecurity professionals!