A new security exploit affecting a number of Nexus smartphones has been made public, revealing a fault with the way the devices handle Flash SMS. The vulnerability, discovered by Bogdan Alecu, can force a device to remotely reboot, freeze, and face connectivity issues as a result.
Flash SMS is a special class of text message that by default is not stored by the system and triggers no audio alert. These are typically encountered as system alerts. When received on an Android device, such a message takes priority, popping up over any open apps or windows. In the case of the Nexus exploit, if a device such as the Galaxy Nexus, Nexus 4, or Nexus 5 receives a number of these messages in succession without dismissal, the device will behave in erratic ways.
The most typical response is a random reboot, but the issues is often compounded by connectivity issues once power is restored to the device. While the exploit creates no immediate concerns in terms of data security and does not allow a would-be hacker to access sensitive info or otherwise take control of a user’s handset, it could be used to perform denial-of-service attacks in the same vein as those used to take websites offline.
Android devices, by default, offer no easy way for users to send Flash messages, though there are several apps available to do so. Alecu even offers his own in conjunction with a Flash SMS firewall, designed with the express purpose of preventing an attack via this method.
The root of the issue most likely stems from the way Nexus devices handle memory storage. The large number of Flash messages required suggests the device becomes overloaded to the point where the messaging app either crashes or the handset becomes unresponsive. Alecu has alerted Google to the issue and a fix was expected in Android 4.3. However, this does not seem to be the case based on his latest tests. Non-Nexus Android devices are unaffected.