iOS devices, including iPhones and iPads, are not able to join WiFi networks with names such as “%p%s%s%s%s%n”, researcher Carl Shou found. And if they try to, they will not only fail but stop other parts of the phone from working, with it losing all WiFi functionality.
Restoring it is relatively easy, if a user knows how, and the bug does not seem to do any permanent damage to the phone or expose it to any other attacks. What’s more, the WiFi network is so strangely named that users are unlikely to ever join one in the first place.
But the strange bug is an unusual flaw in the iPhone and a reminder of an issue that is largely fixed in most modern devices.
It is also redolent of previous bugs where iPhones have not been able to handle certain characters. Often referred to as “text bombs”, there have been numerous instances of certain strings of text causing phones to crash if they were sent over text, for instance.
As in that case, it is probably more likely that the bug would used by someone attempting to prank or annoy an iPhone user, rather than for hacking or more malicious attacks.
Mr Shou said that he had found the issue in iOS 14.4.2, but numerous users found that it was still active in iOS 14.6, the latest version of the operating system that is available to consumers. It is likely to be fixed in an upcoming update, which Apple issues regularly.
It is not clear why the unusual set of letters causes the phone to crash. But many programming languages use the percentage sign as a key part of their code, and so the iPhone is probably attempting to read it as code before finding that it cannot, and terminating the process.
If someone is hit by the problem, it is not immediately obvious how to fix it. Turning WiFi off and on does not solve it, for instance – in fact, it is not possible to do so, because the bug stops that screen from loading – and the issue remains even if the phone is rebooted or the network renamed.
But it is relatively easy to solve it by heading to the Settings app, clicking general and then reset, and choosing the option to “Reset Network Settings”. That will have the effect of resetting all the existing network settings on the phone – including VPN settings or other WiFi networks – but that will include the problem one, and you should be able to get back online.