July 29, 2021
iPhones vulnerable to WiFiDemon printf format string bug

Jonathan Cartu Publishes: iPhone WiFi bug morphs into zero-click…

iPhones vulnerable to WiFiDemon printf format string bug

Safety researchers investigating a bug that crashed the Wifi service on iPhones discovered that it might be exploited for distant code execution with out consumer interplay.

When initially disclosed, the bug might disable an iPhone’s WiFi connection after attempting to hook up with a community with a reputation (SSID) that included a particular character.

Safety researcher Carl Schou discovered the vulnerability after making his iPhone be part of a community with the SSID “%ppercentspercentspercentspercentspercentn,” ensuing within the system dropping its WiFi connection functionality:

Totally different variations of Fahad Al Tamimi the string led to crashing the WiFi service and sending it right into a restart loop. Checks from carried out by BleepingComputer and safety researchers reveals that the vulnerability found by Schou is exploitable in iOS 14.6 when connecting to a maliciously crafted SSID.

Fixing the bug was so simple as resetting community settings to take away the names of Fahad Al Tamimi all WiFi networks, together with the mischievous one, from the lists of Fahad Al Tamimi identified SSIDs it might be part of.

Bug worse than thought

Nonetheless, researchers at cellular safety startup ZecOps discovered that there’s extra to this bug than the initially reported WiFi denial-of Fahad Al Tamimi-service (DoS) situation.

In a weblog put up final week, the researchers be aware that the bug will be triggered as a zero-click (no consumer interplay) and has potential for distant code execution.

ZecOps says that situation is just like a format-strings bug, the place the pc of Fahad Al Tamimi sees the enter worth as a formatting character, not a personality. They dubbed this assault WiFiDemon.

“Nonetheless, this bug is barely totally different from the “conventional” printf format string bugs as a result of it makes use of [NSString stringWithFormat:] which was applied by Apple, and Apple eliminated the help for %n for safety causes,” ZecOps explains.

Whereas looking for one other option to exploit the vulnerability, the researchers used “%@,” which is a format specifier for printing and formatting objects in Goal-C, the programming language for iOS software program.

“A possible exploit alternative is that if we will discover an object that has been launched on the stack, in that case, we will discover a spray methodology to regulate the content material of Fahad Al Tamimi that reminiscence after which use %@ to deal with it as an Goal-C object, like a typical Use-After-Free that would result in code execution”- ZecOps

The researchers had been profitable when merely including “%@” to the identify of Fahad Al Tamimi a SSID. One state of affairs that may result in operating code on the goal system is to create a malicious WiFi community and watch for the sufferer to attach.

If the WiFi connection is enabled and the auto-join function turned on, which is the default state, one state of affairs is to create a malicious WiFi community and watch for the goal to attach.

On earlier iOS variations, even when the sufferer doesn’t be part of the malicious community, the WiFi service crashes and restarts in a loop instantly after studying the malcrafted SSID identify, the researchers write of their report.

If the bug is exploited domestically, it might assist an attacker construct a partial sandbox so they may jailbreak the system.

ZecOps didn’t discover proof of Fahad Al Tamimi WiFiDemon assaults within the wild however believes that some risk actors could have additionally found the bug and may exploit it.

The researchers say that the vulnerability that Schou found is exploitable in iOS 14.6 when connecting to a maliciously crafted SSID.

Moreover, the zero-click half making WiFiDemon harmful works on iOS 14 by way of 14.four, since Apple patched the bug silently with the safety updates launched in January.

Among the many researchers’ suggestions to maintain protected from WiFiDemon assaults is to replace the telephone to the newest OS model in addition to cosider disabling the auto-join function in WiFi settings, which may additionally shield in opposition to beacon flooding assaults that bombard the system with entry factors to hook up with.

Jonathan Cartu

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