Charlie Miller, the winner of two consecutive editions of the Pwn2Own hacking contest, is signaling that a critical vulnerability exists in the way iPhones handle their text messages. According to the security expert, an attacker could exploit the hole even to turn on the phone's microphone to eavesdrop on a conversation.

The news comes via a PC Advisor report citing Miller as saying that Apple is already working to fix the iPhone vulnerability in question. In the simplest terms, the bug found by Miller could allow an attacker to remotely install and run unsigned software code with root access to the phone. The security expert could not disclose too much information about the vulnerability, citing an agreement with Apple. Usually, in such a situation, those who find a bug and report it to the company responsible for the software must wait until a patch is made available, so they can go public with it.

According to the PC Advisor report, Miller said that the SMS vulnerability could, indeed, allow an attacker to run software code on the phone that was sent by SMS over a mobile operator's network, even though the service allowed for a maximum of 140 bytes per message to be sent. As users should know, longer sequences can be sent to the phone as multiple messages that combine into one, when received.

“The malicious code could include commands to monitor the location of the phone using GPS, turn on the phone's microphone to eavesdrop on conversations, or make the phone join a distributed denial of service attack or a botnet,” Miller is cited as saying. “SMS is a great vector to attack the iPhone,” he added. Admittedly, “The iPhone is more secure than OS X,” Miller pinpointed, “but SMS could be a critical vulnerability.”

Needless to point out, iPhone software update 3.1 or 3.0.1 should become available soon to fix this and other potential issues.