Close-up photo of Wi-Fi settings on a smartphone.

There’s a bug in iOS that disables Wi-Fi connectivity when gadgets be a part of a community that makes use of a booby-trapped title, a researcher disclosed over the weekend.

By connecting to a Wi-Fi community that makes use of the SSID “%ppercentspercentspercentspercentspercentn” (citation marks not included), iPhones and iPads lose the power to affix that community or every other networks going ahead, reverse engineer Carl Schou reported on Twitter.

It didn’t take lengthy for trolls to capitalize on the discovering:

An absence of malice

Schou, who’s the proprietor of hacking useful resource Secret Membership, initially noticed no straightforward method to restore Wi-Fi capabilities. Finally, he discovered that customers may reset community performance by opening Settings > Basic > Reset > Reset Community Settings.

Apple representatives didn’t reply to emailed questions, together with if there have been plans to repair the bug and whether or not it affected macOS or different Apple choices.

Schou stated in an Web message that the bug is brought on by the inner logging performance within the iOS Wi-Fi daemon, which makes use of the SSID within format expressions. The situation makes it potential in some circumstances for unauthorized format strings to be injected into delicate elements of the extremely fortified Apple OS. He and different safety consultants, nonetheless, stated there was little probability of the bug being exploited maliciously.

“For my part, the real-world menace is minimal as you might be fairly constrained by the size of the SSID and the format expression itself,” he defined. “You might doubtlessly flip this into an info disclosure within the logger, however I don’t suppose it’s even remotely potential to get code execution.”

A fast evaluation of the bug by an out of doors researcher agreed that it isn’t seemingly the bug may very well be exploited to execute malicious code. The evaluation additionally discovered that the bug seems to stem from a flaw in an iOS logging element that makes use of the concat perform to successfully convert the SSID string right into a format string earlier than writing it to the log file.

As a result of the strings aren’t echoed to delicate elements of the iOS, a hacker is unlikely to reach abusing the logging function maliciously. In addition to that, an exploit would require an individual to actively be a part of a community that comprises a suspicious-looking title.

“For the exploitability, it doesn’t echo and the remainder of the parameters don’t appear to be controllable,” the researcher wrote. “Thus I don’t suppose this case is exploitable. In any case, to set off this bug, it’s worthwhile to hook up with that WiFi, the place the SSID is seen to the sufferer. A phishing Wi-Fi portal web page may as properly be simpler.”


Not all researchers reached the identical evaluation. Researchers from safety agency AirEye, as an example, stated that the approach may very well be used to bypass safety home equipment that sit on the perimeter of a community to dam unauthorized knowledge from getting into or exiting.

“What we discovered was that though the newest iPhone Format String flaw is perceived as seemingly benign, the implications of this vulnerability stretch far and past any joking matter,” AirEye researcher Amichai Shulman wrote. “In case you are liable for the safety of your group, you have to be conscious of this vulnerability as a associated assault can have an effect on company knowledge whereas bypassing widespread safety controls resembling NAC, firewalls and DLP options.”

Shulman additionally stated that macOS is affected by the identical bug. Ars couldn’t instantly confirm this declare. Schou stated he hasn’t examined macOS however that others have reported they have been unable to breed the error on the OS.

The actual story

Schou instructed me that the community crashes don’t occur each time an iOS gadget connects to a malicious SSID. “It is nondeterministic, and generally you might be fortunate sufficient that the Wi-Fi daemon crashes with out it persisting the SSID,” he defined. The flaw has existed since no less than iOS 14.4.2, which was launched in March, and probably for years earlier than that.

He stated he found the bug when he linked an iPhone to one in all his wi-fi routers. “All of my gadgets are named after numerous injection strategies to mess with previous gadgets that don’t sanitize enter,” Schou stated. “And apparently, the newest iOS.”

The crash is brought on by what researchers name a uncontrolled format string bug. The flaw arises when corrupted consumer enter is the format string parameter in sure capabilities written in C and C-style languages. Use of format tokens resembling %s and %x can in some circumstances print knowledge to reminiscence. The bug was initially thought of innocent. Extra lately, researchers have acknowledged the potential for writing malicious code utilizing the %n format token.

Probably the most shocking factor about this bug is the truth that it exists in any respect. A large assortment of programming pointers exists for stopping all these format string flaws. The failure of what’s arguably the world’s most safe shopper OS to adequately implement these strategies in 2021 is the actual story right here.

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