Researchers at HP’s Zero Day Initiative have disclosed full details and proof-of-concept exploit code for a series of bugs they discovered that allow attackers to bypass a key exploit mitigation in Internet Explorer.
The disclosure is a rarity for ZDI. The company typically does not publish complete details and exploit code for the bugs it reports to vendors until after the vulnerabilities are fixed. But in this case, Microsoft has told the researchers that the company doesn’t plan to fix the vulnerabilities, even though the bugs were serous enough to win ZDI’s team a $125,000 Blue Hat Bonus from Microsoft. The reason: Microsoft doesn’t think the vulnerabilities affect enough users.
The vulnerabilities that the ZDI researchers submitted to Microsoft enable an attacker to fully bypass ASLR (address space layout randomization), one of the many mitigations in IE that help prevent successful exploitation of certain classes of bugs. ZDI reported the bugs to Microsoft last year and disclosed some limited details of them in February. The researchers waited to release the full details until Microsoft fixed all of the flaws, but Microsoft later informed them that they didn’t plan to patch the remaining bugs because they didn’t affect 64-bit systems.
“In this situation, Microsoft’s statement is technically correct – 64-bit versions do benefit from ASLR more than 32-bit versions. A 64-bit system has a much larger address space than a 32-bit system, which makes ASLR that much more effective. However what is lost here is that the bypass described and submitted only works for 32-bit systems, which is the default configuration on millions of systems. To demonstrate this, we have released proof-of-concept (PoC) code to demonstrate this bypass on Windows 7 and Windows 8.1,” a blog post from Dustin Childs of HP says.
Childs, who is a former Microsoft security official, said ZDI is releasing the details and PoC code in order to give users as much information as possible to defend themselves against potential attacks.
“Since Microsoft feels these issues do not impact a default configuration of IE (thus affecting a large number of customers), it is in their judgment not worth their resources and the potential regression risk. We disagree with that opinion and are releasing the PoC information to the community in the belief that concerned users should be as fully informed as possible in order to take whatever measures they find appropriate for their own installations,” he said.
Microsoft did not provide a comment in time for publication of this story.