Pierluigi Paganini December 14, 2017

Security researchers at Trend Micro have publicly disclosed an unpatched zero-day flaw in the firmware of AT&T DirecTV WVB kit after manufactured failed to patch it

Security researchers at Trend Micro have discovered an unpatched zero-day vulnerability in the firmware of AT&T DirecTV WVB kit after the manufacturer failed to patch this flaw over the past few months.

The issue affects a core component of the Genie DVR that’s shipped free of cost with DirecTV. The flaw can be easily exploited by attackers to gain root access to the device, posing millions DirecTV service users at risk.

The vulnerability resides in WVBR0-25, a Linux-powered wireless video bridge manufactured by Linksys.

DirecTV Wireless Video Bridge WVBR0-25 allows the Genie DVR to communicate over the air with customers’ Genie client boxes that are plugged into their TVs in the same home.

The Trend Micro expert Ricky Lawshae analyzed the kit and discovered that Linksys WVBR0-25 doesn’t implement any authentication to access internal diagnostic information from the device’s web server.

The expert discovered that accessing the wireless bridge’s web server on the device it was possible to see a text streaming.

“I started out by trying to browse to the web server on the device. I expected to find a login page of some sort. What I found instead was a wall of text streaming before my eyes.” wrote Ricky Lawshae.

The output of several diagnostic scripts was containing a lot of information about the DirecTV Wireless Video Bridge, including the WPS pin, running processes, connected clients, and much more.

A deeper analysis of the scripts revealed that the device was accepting commands remotely with a “root” access, meaning that an attacker could have taken full control over it.

“The return value also showed the device had happily executed my new commands and executed them as the root user, too! No login prompt. No input sanitization.” continues the analysis.

“It literally took 30 seconds of looking at this device to find and verify an unauthenticated, remote root command injection vulnerability. It was at this point that I became pretty frustrated,”  

“The vendors involved here should have had some form of secure development to prevent bugs like this from shipping. More than that, we as security practitioners have failed to affect the changes needed in the industry to prevent these simple yet impactful bugs from reaching unsuspecting consumers.”

Lawshae also published a video PoC demonstrating how to easily get a root shell on the DirecTV wireless box in less a few seconds.

The vulnerability was promptly reported by the ZDI Initiative to Linksys more than six months ago, but the vendor had yet not fixed the problem, for this reason, the expert opted to publicly disclose the zero-day vulnerability.

Pierluigi Paganini

(Security Affairs – AT&T DirecTV WVB kit, hacking)

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