Pierluigi Paganini November 16, 2019

A working exploit for the checkm8 BootROM vulnerability is now available and security experts fear that threat actors could use is in attacks in the wild.

This week, the “unpatchable” jailbreak, known as Checkra1n, for the checkm8 BootROM vulnerability was officially released potentially threatening millions of devices.

“This release is an early beta preview and as such should not be installed on a primary device. We strongly recommend proceeding with caution.” reads the page set up for the checkra1n exploit.

In September, the security expert Axi0mX released a new jailbreak, dubbed Checkm8, that works on all iOS devices running on A5 to A11 chipsets. The jailbreak works with all Apple products released between 2011 and 2017, including iPhone models from 4S to 8 and X.

The expert who devised the Checkm8 jailbreak described it as “a permanent unpatchable bootrom exploit,” anyway it is essential to highlight that the exploit could lead to a jailbreak by chaining it with other flaws.

Bootrom jailbreaks are very dangerous because they are permanent and can’t be addressed via software, in order to patch a Bootrom flaw it is necessary to physical modify the chipsets.

Axi0mX’s jailbreak code is marked as a “beta” release, but experts warned of the concrete possibility that expert coders or intelligence agencies will integrate it into hacking tools and malware. Experts pointed out that the jailbreak needs physical access to the device, so and could not be used remotely.

Now, checkm8 BootROM vulnerability has a working exploit, the checkra1n iPhone jailbreak, that is publicly available.

“Checkra1n is unprecedented in potential impact, with millions of devices at risk as a result of the extensive device and iOS targets,” said Christopher Cinnamo, senior vice president of product management at Zimperium.

The tool leverages the checkm8 BootROM exploit that was released in September, but experts warn that it is not correct to consider the jailbreak permanent because, as explained by Christoph Hebeisen, head of security research at Lookout, “the device will be ‘un-jailbroken’ by a reboot.”

This limitation could be overwhelmed by gaining persistence with a malicious app that executes the exploit after the reboot.

Experts explained that it is not easy to use the exploit to jailbreak a target’s device because it needs the physical access to an unlocked iPhone and tethering it to a macOS computer running the exploit code.

However, the risk of exploitation is concrete in multiple scenarios, such the control while crossing international borders of countries where there is a strict censorship.

In July, the media reported that Chinese border guards are secretly installing a surveillance app on smartphones of tourists and people crossings in the Xinjiang region who are entering from Kyrgyzstan.

“[An attack] can happen with device theft or when a device must be handed over for inspection while crossing international borders. For example, a few months ago it was reported that Chinese border guards put secret surveillance app on tourists’ phones,” explained Hebeisen. 

Because Checkra1n leverages the unpatchable checkm8 vulnerability in the BootROM, the only way to mitigate protect the devices from the exploit is by upgrading devices to an iPhone XR or more recent.

Pierluigi Paganini

(SecurityAffairs – Checkra1n exploit, checkm8)

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