Some Network Names Disable Wi-Fi on iPhones

By Lore Apostol / July 5, 2021

Another iOS Wi-Fi SSID (access point name) bug has been discovered that disables Wi-Fi on iPhone. A researcher discovered that the issue stems from a character in network names that could altogether disable Wi-Fi on iPhones.

Security researcher Carl Schou found that this bug comes from the percent ("%") symbol. The real problem is that it also requires a complete hard reset of the iPhone to work again.

Connecting to a Wi-Fi with this SSID creates a fault in the Wi-Fi module of the iPhone, causing it to shut down and stop working. In C coding language, the percent symbol is used to insert a variable in a string - and since the network name starts with "%", the iOS software expects an input that never comes, resulting in arbitrary code input and malfunction. Of course, you can always try to avoid connecting to network that have this symbol in their name.

This discovery comes after the same researcher found that if he connected to a network with the SSID name "%p%s%s%s%s%n" on an iPhone or iPad, it would cause a bug in iOS’ networking software that would disable its Wi-Fi and system networking features like AirDrop.

If you are affected by this, don't panic. You can reset all saved Wi-Fi networks on the iPhone by following this path: in Settings, go to General -> Reset -> Reset Network Settings. After this, you should be able to connect to your home router or hotspot without issues.

Apple has recently released an update for iOS 12, fixing two actively exploited bugs in the WebKit engine that brings a third fix concerning a memory corruption problem in the ASN.1 decoder. Most probably, Apple will release a fix for this repeating bug as well.

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