Certain WLAN names paralyze the network capability of iPhones
An incorrect connection is enough, then the iPhone can no longer establish network connections. (Photo: Shutterstock)
A sequence of so-called format strings in the SSID not only prevents iPhones from finding the corresponding network, but also completely deactivates the function. But there is a remedy.
The security expert Carl Schou has discovered a sequence of characters that causes the WLAN components of iOS devices to fail. This is the name “% p% s% s% s% s% n”. He tried to connect to a WLAN with this name and found that the device could no longer be persuaded into any network activities. In addition to WiFi, this also applied to airdrop connections. Even after a restart, the problem persisted.
After joining my personal WiFi with the SSID “% p% s% s% s% s% n”, my iPhone permanently disabled it’s WiFi functionality. Neither rebooting nor changing SSID fixes it: ~) pic.twitter.com/2eue90JFu3
– Carl Schou (@vm_call) June 18, 2021
Contents
Stay away from WLANs with “%” in their names
The failure of the network component is probably due to the use of so-called format strings of the type% [Buchstabe]. As early as the late 1990s, there was a method of bypassing the system’s internal filters using format strings and thus giving instructions to the target device. Other specialists checked Schou’s bug and came to the conclusion that the command sequence caused a buffer overflow in the WLAN component. Excessive amounts of data end up in a reserved memory area, so that memory areas that are outside of it are also overwritten. The result is crashes and even damage to data structures. Modern programming languages automatically monitor the limits of memory areas.
Remedy costs noted networks
In order to release the network components deactivated by the memory overload, those affected must reset the settings. You can do this in iOS under Settings / General / Reset / Network settings. In doing so, however, you lose all the settings you have made, for example the saved WiFi networks including passwords. According to Shou, no malicious code can be executed through the hole.
It’s not iOS’s first SSID problem. In the past, the operating system had problems with hyphens. Most recently, users did not receive any notifications about their messages in iOS 14.2 – the problem is said to have been resolved by now. Apple built the biggest network scandal in recent times into macOS 11.3 Big Sur: The system deactivates the firewall in order to send data to Apple undisturbed.
