A security researcher has found that some Wi-Fi networks with the percent symbol (%) in their name can turn off Wi-Fi on iPhones and other iOS devices. Carl Schou tweeted that if an iPhone is within range of a network named% secretclub% power, the device will not be able to use Wi-Fi or any related functionality, and even after resetting the network settings, the bug may continue to show the Wi-Fi on the device inoperable.
– Carl Schou (@vm_call) July 4, 2021
A few weeks ago, Schou and his nonprofit group, Secret Club, which reverse engineer software for research purposes, discovered that if an iPhone connects to a network with the SSiD name% p % s% s% s% s% n this would cause a bug in iOS’s networking stack that would disable its Wi-Fi, and system networking features like AirDrop would become unusable.
9to5 Mac offered a possible explanation for the strange bug:
the ‘%[character]The ‘syntax is commonly used in programming languages to format variables in an output string. In C, the specifier ‘% n’ means to store the number of characters written in the format string in a variable passed to the format string function. The Wi-Fi subsystem likely forwards the unchecked Wi-Fi network name (SSID) to an internal library that performs string formatting, which in turn causes arbitrary memory write and memory overflow. buffer. This will cause memory corruption and the iOS watchdog will kill the process, effectively disabling Wi-Fi for the user.
We’ve reached out to Apple to see if this works on a fix, and will update if we hear from them. But as 9to5 Mac Notes, the bug can probably be avoided by not connecting to Wi-Fi networks with percentage symbols in their names.