A security researcher found that certain Wi‑Fi networks with the percent sign (%) in their names can disable Wi‑Fi on iPhone and other iOS devices. Carl Schou wrote on Twitter that if an iPhone is within range of a network called %secretclub%power, the device will not be able to use Wi‑Fi or other related functions and even after resetting network settings, the bug may continue to render Wi‑Fi unusable on the device.
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A few weeks ago, Schou and his nonprofit group, Secret Club, found that connecting an iPhone to a network named %p%s%s%s%s%n would trigger a bug in the iOS networking stack that would disable its Wi-Fi, rendering the system's networking features like AirDrop useless.
9to5 Mac offered a possible explanation for the strange bug:
The syntax «% [character]» is commonly used in programming languages for formatting variables into an output string. In C, the specifier «%n» means storing the number of characters that have been written to the format string into a variable passed to the string formatting function. The Wi‑Fi subsystem possibly passes the Wi‑Fi network name (SSID) that has not been modified to some internal library that performs string formatting, which causes arbitrary memory writes and a buffer overflow. This will lead to memory corruption and the iOS watchdog will “kill the process”, effectively disabling Wi‑Fi for the user.
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Apple so far has not been mentioned on the issue or any possible fix of the problem. But as 9to5 Mac notes, the bug can probably be avoided by not connecting to Wi‑Fi networks that contain percent symbols in their names.
Source of information: theverge.com
