Yet another eavesdrop vulnerability in Cisco phones

Security groundhog day


A university student presenting at the Amphion Forum has demonstrated turning a Cisco VoIP phone into a listening device, even when it’s on the hook.

According to Dark Reading, the vulnerability demands a fairly extensive reconfiguration of the phone. This, at least, means the attacker needs greater sophistication than previous eavesdropper attacks reported by The Register in 2007 and 2011.

A number of 7900-series phones are affected, according to Forbes.

The latest vulnerability is based on a lack of input validation at the syscall interface, according to Columbia University graduate student Ang Cui. This, Cui said, “allows arbitrary modification of kernel memory from userland, as well as arbitrary code execution within the kernel. This, in turn, allows the attacker to become root, gain control over the DSP [Digital Signal Processor], buttons, and LEDs on the phone.”

In the demonstration, Cui modified the DSP to surreptitiously turn on the phone’s microphone and stream its output to the network.

To simplify the demonstration, Cui programmed the necessary reconfiguration onto an external circuit which he plugged into the phone’s Ethernet port, and then captured what was spoken near the VoIP phone on his smartphone.

Cui told Dark Reading that the phones contain a number of vulnerable third-party libraries, which he promises to discuss at the upcoming Chaos Computer Conference, 29C3.

Cisco says workarounds and a software patch are available to address the issue, tagged with the bug id CSCuc83860. ®

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