Checkm8 Exploit Opens Door to Unpatchable Jailbreak on iPhone 4S Through iPhone X - MacRumors
Skip to Content

Checkm8 Exploit Opens Door to Unpatchable Jailbreak on iPhone 4S Through iPhone X

A security researcher who goes by "axi0mX" on Twitter today released "checkm8," which he claims is a bootrom exploit for iOS devices equipped with A5 through A11 chips, including the iPhone 4S through iPhone X, several iPad models dating back to the iPad 2, and the fifth-generation iPod touch and later.

trio iphones ios
This would be the first publicly released bootrom exploit since the iPhone 4 in 2010 and pave the way for a permanent, non-patchable jailbreak on hundreds of millions of affected iOS devices. Since the bootrom is read-only, Apple cannot patch this type of exploit with a software update.


The bootrom exploit has many other possibilities on affected devices, including downgrading iOS versions without SHSH blobs or APTickets, dual booting iOS, and running custom firmwares, according to jailbreak enthusiasts.

This is significant news in the jailbreaking community, as the last bootrom exploit known as "limera1n" was released by George "geohot" Hotz nearly a decade ago for devices with A4 chips and earlier, including the iPhone 4, iPhone 3GS, the third- and fourth-generation iPod touch, and the original iPad.

Popular Stories

Apple Event Logo

Apple's Next Era Begins September 1

Thursday May 7, 2026 10:36 am PDT by
Apple recently announced that Tim Cook will be stepping down as CEO later this year, after 15 years of leading the company. Effective September 1, Apple's hardware engineering chief John Ternus will become the company's next CEO, while Cook will become executive chairman of Apple's board of directors. In his new role, Apple said Cook will assist with "certain aspects" of the company,...
Instagram Feature 2

PSA: Instagram Encrypted Messaging Ends on Friday, May 8

Tuesday May 5, 2026 8:24 am PDT by
Instagram will remove end-to-end encryption for direct messages between users from May 8, 2026. When the date comes around, Meta will potentially be able to see the contents of all messages between users on the social media platform. Encrypting messages has been an optional feature in Instagram since 2023, but in March of this year the social media platform quietly updated a help page to say ...
Apple Event Logo

Apple Just Released a New Accessory

Monday May 4, 2026 8:13 am PDT by
Apple today released a new Pride Edition Sport Loop for the Apple Watch. The band features a rainbow design with 11 colors of woven nylon yarns. The new Pride Edition Sport Loop is available to order now on Apple.com and in the Apple Store app in 40mm, 42mm, and 46mm sizes, and it will be available at Apple Store locations starting later this week. In the U.S., the band costs $49. There...

Top Rated Comments

zorinlynx Avatar
86 months ago

This can't be good for the security of these devices...

And have malware installed or spying on you. No thanks. Apple should have gotten their sh** together and not have had the exploit open for nearly a week.
This is a bootrom exploit. It can only be exploited when the device is in DFU recovery mode and will not affect the security of devices being used normally.

This is really the best kind of jailbreak exploit because only the people who really want to go out of their way to jailbreak can use it. Regular users are safe; all it means is that people can do whatever they like with these devices they own now.
Score: 35 Votes (Like | Disagree)
itsmilo Avatar
86 months ago

All the cool kids violate their warranty. Didn't you know?
one restore on iTunes and your warranty is „restored“ so to speak
Score: 28 Votes (Like | Disagree)
tobefirst ⚽️ Avatar
86 months ago
I haaaaaaate the new force press/haptic touch menu on iOS 13. I would consider jail breaking just to go back to how that worked on my X on iOS 12.
Score: 16 Votes (Like | Disagree)
Jeremy1026 Avatar
86 months ago
I haven't been jailbroken since the 3G, what's the big draw of a jailbreak now a days?
Score: 15 Votes (Like | Disagree)
86 months ago

Is there anything exciting going on in the jailbreaking community anymore? Aside from using Apps you don't pay for, is there a reason to jailbreak anymore?
Yes. I have a dash/console integrated iPad Mini 2 in my 1981 DeLorean. It is connected via lightning cable to a Sony headunit installed in a cubby behind the seat. By using Sony's AppRemote app, I can control all stereo functions from the iPad itself. With the iPad being jailbroken, I can enable even more functionality---for example, I have Activator installed to automatically unlock the iPad when the iPad receives power (in other words, the key gets turned and the iPad gets unlocked). I also have it set to open the AppRemote software immediately after being unlocked. Little tweaks like this are nice to have and can only be obtained for me via jailbreaking.

Attachment Image
Score: 14 Votes (Like | Disagree)
Krevnik Avatar
86 months ago

Once the data is copied off the phone can't you brute force it without fear of being locked out? What's the encryption like?
You can read through the details yourself if you want: https://www.apple.com/business/docs/site/iOS_Security_Guide.pdf

The NAND itself is encrypted with AES 256. The passcode is the weak point, but to generate the AES 256 key from the passcode, you need the passcode and the unique AES 256 key burned into the Secure Enclave on the SOC. The passcode is run through PBKDF2 and then tangled with the AES 256 key in a one-way operation.

So dumping the flash raw means you face AES 256 at full strength, even if you know the passcode, because you also need the AES 256 key from the SOC to be able to recreate the key yourself if you aren't just brute forcing AES.

The fastest way to crack an iPhone is to brute force the passcode and bypass the lockout on attempts if you can. It also gives you the most access to the content.

Individual containers/files can be encrypted with separate keys based on the level of access the OS should have in different states of lock/unlock, on top of the NAND encryption. So if you dump the flash unencrypted, you then also need to crack the containers for things like email and messages which are also AES 256 encryption. All the more reason to focus even more on the passcode and attempt lockout mechanisms.


This is a bootROM exploit. Every iPhone ever manufactured excluding the iPhone XS and 11 series will always be vulnerable to this exploit regardless of any iOS updates. There is no patch.
Apple still manufactures the iPhone 8 and 3rd Gen Air. I wouldn't be surprised if we see manufacturing runs of those that include the patched boot ROM.
Score: 14 Votes (Like | Disagree)