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New malformed Wi-Fi name bug can require iPhone factory reset to fix

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A bug in the way iOS handles Wi-Fi hotspot names is apparently worse than first thought, with one malformed SSID found to disable Wi-Fi access on an iPhone completely, requiring a factory reset to rectify it.

In June, security researcher Carl Schou discovered a personal Wi-Fi hotspot name of "%p%s%s%s%s%n" causes problems for iOS devices. It was found that iPhones simply couldn't connect to the hotspot, and in fact disabled Wi-Fi connectivity in some instances.

While that issue could be fixed by reseting the network settings within iOS, Schou has since discovered a variant along the same lines that can cause more harm to an unsuspecting iPhone. According to Schou in a tweet on Sunday, using the SSID "%secretclub%power" can disable an iOS device's Wi-Fi capabilities, with no guarantee that a network settings reset will restore connectivity.

Schou claims the iPhone used to test still didn't have Wi-Fi after repeated resets of network settings and a forced restart of the iPhone. The researcher has also contacted Apple's device security team over the matter, but has yet to hear anything back.

The original bug was believed to be an issue with input parsing, where the percentage sign could be misinterpreted by iOS as a string-format specifier, namely that characters following the symbol could be considered a variable or a command instead of plain text.

While the new SSID does jokingly promote Secret Club, a technology exploration group Schou is involved with, the use of the percentage signs followed by the characters S and P are most likely the problem areas for the hotspot name bug. Analysis of the issue confirms a format string bug is behind it, though it doesn't seem to be a highly exploitable vulnerability for a bad actor.

It is highly likely that there are many more combinations of text strings that could cause problems within iOS in this manner, but only until the bug is patched out by Apple. While the company is beta-testing iOS 14.7 and iOS 15, it is unclear if the issue will be fixed in those releases by the company.

For the moment, AppleInsider recommends users don't connect to unfamiliar Wi-Fi access points, especially if they include unusual symbols.

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