iOS bug sends iPhones into endless crash cycle when exposed to rogue Wi-Fi

There's a bug in Apple's iOS 8 that allows nearby attackers to send apps—and in some cases the iPhone or iPad they run on—into an endless reboot cycle that temporarily renders the devices useless, according to researchers who demonstrated the attack Tuesday.

The exploit uses a standard Wi-Fi network that generates a specially designed secure sockets layer (SSL) certificate to exploit the bug, according to the researchers, who work for Israel-based Skycure. The encrypted communication causes whatever apps happen to be connected to the booby-trapped Wi-Fi network to crash. The vulnerability was introduced in version 8 of the Apple mobile operating system.

After sustained connections to the malicious signal, the OS itself will crash, in some cases in a way that causes the devices it runs on to spiral into a repeatable reboot cycle. Making the attack particularly vexing, even if users know the endless crashes are generated by the Wi-Fi network they're connected to, they can't disconnect because the repeated restarts make it impossible to access the device's user settings, as demonstrated in the following video:

The Skycure researchers said the exploit can be combined with one they uncovered two years ago that forces iPhones to automatically connect to rogue Wi-Fi networks. The combination allows attackers to form a "NO iOS Zone" that after luring all iOS devices to join the Wi-Fi network, sends them into an endless crash cycle. Targets hit by the attack would have few options to stop the attack as long as they're within range of the Wi-Fi access point. Skycure documented the vulnerability in a blog post published Tuesday and demonstrated it the same day at the RSA security conference in San Francisco.

The post says that Skycure has already privately reported the vulnerability to Apple. Until there's a patch, iPhone and iPad users should make sure they're using iOS 8.3, since it appears to have mitigated some of the effects of the bug. Users should also keep Wi-Fi on their device turned off except when it's needed. Users can also install apps that give them control over which SSIDs an iPhone or iPad will and will not connect to.

Skycure is withholding technical details about the specific conditions that cause Wi-Fi networks to carry out the crash attack to prevent miscreants from repeating them. There's no indication the attacks are being carried out in the wild right now.