French security company Vupen said today that it's figured out how to hack Google's Chrome by sidestepping not only the browser's built-in "sandbox" but also by evading Windows 7's integrated anti-exploit technologies.

Google said it was unable to confirm Vupen's claims.

"The exploit ... is one of the most sophisticated codes we have seen and created so far, as it bypasses all security features including ASLR/DEP/Sandbox," said Vupen in a blog post Monday. "It is silent (no crash after executing the payload), it relies on undisclosed ('zero-day') vulnerabilities and it works on all Windows systems."

Vupen posted a video demonstration of its exploit on YouTube.

According to Vupen, its exploit can be served from a malicious Web site. If a Chrome user surfed to such a site, the exploit executes "various payloads to ultimately download the Calculator from a remote location and launch it outside the sandbox at Medium integrity level."

Vupen used the Windows Calculator only as an example: In an actual attack, the "calc.exe" file would be replaced by a hacker-made payload.

Historically, Chrome has been the most difficult browser to hack, primarily because of its sandbox technology, which is designed to isolate Chrome from the rest of the machine to make it very difficult for a hacker to execute attack code on the PC.

For example, Chrome has escaped unscathed in the last three Pwn2Own hacking contests, an annual challenge hosted by the CanSecWest conference in Vancouver, British Columbia, and sponsored by HP TippingPoint's bug bounty program.

Last March, a team from Vupen walked away with a $15,000 cash prize after hacking Safari, the Apple browser that, like Chrome, is built on the open-source WebKit browser engine.

But no one took on Chrome at 2011's Pwn2Own, even though Google had offered a $20,000 prize to the first researcher who hacked the browser and its sandbox.

The Vupen attack code also bypassed Windows 7's ASLR (address space layout randomization) and DEP (data execution prevention), two other security technologies meant to make hackers' jobs tougher.

Vupen said it would not publicly release details of the exploit, or the unpatched bug(s) in Chrome. "This code and the technical details of the underlying vulnerabilities will not be publicly disclosed," said Vupen. "They are shared exclusively with our Government customers as part of our vulnerability research services."

Last year, Vupen changed its vulnerability disclosure policies when it announced it would no longer report bugs to vendors, but instead would reveal its research only to paying customers.

Other security experts reacted today to the news of one or more Chrome zero-days, and to Vupen's practice of providing details only to its clients.

"I suppose that means we have a known Chrome 0-day floating around. That's fun," said Jeremiah Grossman, CTO of WhiteHat Security, in a Twitter message today.

"That also means for that the [government] is outbidding Google for bug bounties," Grossman added in a follow-up tweet.

"For now, the [government] still has more money than Google," chimed in Charlie Miller, the only researcher who has won cash prizes at four straight Pwn2Own contests.

Google, like rival browser maker Mozilla, runs a bounty program that pays independent researchers for reporting flaws in Chrome. Last month, Google paid out a record $16,500 in bounties for bugs it patched in a single update. In the first four months of 2011, Google spent more than $77,000 on bug bounties.

Google cited Vupen's policy of not reporting flaws as the reason it could not verify the French firm's assertions.

"We're unable to verify Vupen's claims at this time as we have not received any details from them," a Google spokesman said. "Should any modifications become necessary, users will be automatically updated to the latest version of Chrome."

Gregg Keizer covers Microsoft, security issues, Apple, Web browsers and general technology breaking news for Computerworld. Follow Gregg on Twitter at @gkeizer or subscribe to Gregg's RSS feed . His e-mail address is gkeizer@computerworld.com.