Researcher releases attack code for just-patched Windows bug

Microsoft fixed flaw nine months after it was revealed at last year's Pwn2Own hacking contest

Attack code for a Windows vulnerability that Microsoft patched last week was released by a researcher one day after the company fixed the flaw.

The bug, which Microsoft rated "critical" -- its highest threat ranking -- was first reported more than nine months earlier when its discoverer used it in a one-two punch against Internet Explorer 8 (IE8) that won him $10,000 in a hacking challenge.

Peter Vreugdenhil, then an independent Dutch researcher but now employed by HP TippingPoint, the sponsor of the Pwn2Own contest, used the vulnerability to sidestep one of Windows 7's most important anti-exploit defenses, ASLR (address space layout randomization).

"I used this to get rid of ASLR, and another vulnerability to bypass DEP," said Vreugdenhil in an interview today. DEP, or data execution prevention, is another protection technology that Microsoft relies on to make it difficult for attackers to execute their malicious code on Windows.

When Vreugdenhil hacked IE8 in under two minutes at last year's Pwn2Own, TippingPoint's Aaron Portnoy called it "technically impressive."

"There were a multitude of reasons why it was so impressive," said Portnoy, the manager of TippingPoint's security research team. "One was the fact that he used two vulnerabilities, each likely exploitable on their own, in tandem. Peter got them to work together."

Vreugdenhil posted one version of the exploit he used at Pwn2Own on his own Web site last Wednesday. That was the day after Microsoft patched the vulnerability in Microsoft Data Access Components (MDAC), a set of components that lets Windows access databases such as Microsoft's own SQL Server. The flaw is in the MDAC ActiveX control that allows users to access databases from within IE.

The attack code may not be much good to criminals as is, said Vreugdenhil, who used later versions of the exploit at the contest.

"It's probably not going to work if you just run it," Vreugdenhil said. "It's more likely that [IE] will crash [because] it's not as reliable as what I used at Pwn2Own."

Although Microsoft fixed Vreugdenhil's other vulnerability in June, it took more than nine months to issue a patch for the MDAC bug he used in the contest.

Portnoy blamed miscommunication and a tracking problem on Microsoft's part for the delay.

"There was some confusion about how Peter's exploit worked," Portnoy said. "They thought that it was non-exploitable, and we had to clarify." Only after Vreugdenhil received clearance to move to the U.S. to take the TippingPoint job did he and Portnoy connect with Microsoft to spell out the vulnerability and the working of the complex exploit.

While Microsoft has repeatedly defended ASLR's and DEP's effectiveness -- it applauded the technologies just days after Vreugdenhil and another researcher evaded both at Pwn2Own -- the company's security engineers have also acknowledged that hackers are finding ways to bypass both by exploiting weaknesses in ASLR.

"They're just hurdles," said Portnoy. "They don't make it impossible [to run attack code], but they do make it harder."

Last month, Microsoft reaffirmed its confidence in ASLR and DEP when Matt Miller of the Microsoft Security Engineering Center (MSEC) said that they "are strong countermeasures for the types of attacks that we see in the wild today despite weaknesses in their current implementations."

Portnoy begged to differ.

"Just because they've seen none in the wild doesn't mean that they haven't been used," Portnoy said. "It just means that Microsoft hasn't seen them."

TippingPoint will again sponsor the Pwn2Own contest at the CanSecWest security conference, which is slated to run March 9-11. Portnoy said TippingPoint would release more information about this year's Pwn2Own early next month, but confirmed that it would highlight browser and mobile exploits.

One change this year is that Pwn2Own will offer cash prizes to researchers who successfully hack into a mobile phone's broadband processor, opening the door for exploits of bugs in the firmware of the chips that process a phone's radio signals.

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Gregg Keizer

Gregg Keizer

Computerworld (US)
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