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By | Dan Goodin 7th January 2011 01:05

Researcher breaks security sandbox in Adobe Flash

Bypassing security with mhtml

A security researcher has found a way to bypass a measure in Adobe's Flash Player that's designed to harden it against hack attacks.

Billy Rios, a Google researcher who published the method on his personal website, said it circumvents the local-with-filesystem sandbox, which is supposed to prevent Flash files loaded locally from passing data to remote systems.

By design, the so-called SWF files are locked in perimeter that can't communicate with the outside world. That's intended to thwart malicious Flash content that would otherwise locate sensitive user data and send it to machines controlled by attackers.

Rios found that the measure can be circumvented using a file:// request to a network machine. After snatching sensitive data, an attacker can simply pass it along using the GET protocol to an address such as file://\\192.168.1.1. That works on local area networks. To pass information to remote servers on the internet, attackers can use various protocol handlers that haven't been blacklisted by Adobe developers.

One such protocol is the mhtml handler, which is available on Windows and can be used without any prompts.

“Using the mhtml protocol handler, it's easy to bypass the Flash sandbox,” Rios wrote.

Well, sort of.

An Adobe spokeswoman issued a statement that read:

An attacker would first need to gain access to the user's system to place a malicious SWF file in a directory on the local machine before being able to trick the user into launching an application that can run the SWF file natively. In the majority of use scenarios, the malicious SWF file could not simply be launched by double-clicking on it; the user would have to manually open the file from within the application itself.

The company's security team has rated the bug “moderate.” ®

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