Security firm Calif.io showed an untethered jailbreak for an iPhone 18 Pro running iOS 27.0.1 on stage Friday at Hexacon, an offensive security conference in Paris. The demo showed the device staying jailbroken after a reboot, making it the first successful permanent untethered jailbreak reported for hardware in this class.
An untethered jailbreak that survives a restart
A jailbreak removes Apple’s software restrictions on the iPhone. In this case, untethered means the jailbreak returns on its own after a restart, without requiring the phone to be connected to a computer.
Apple builds the iPhone as a locked-down system. It relies on signed code, app sandboxing, and a protected boot chain so users cannot alter how iOS works or run software the company has not approved. A jailbreak breaks those restrictions and gives the owner root access, the highest level of control on the device. That access can allow apps outside the App Store, interface changes, added features, and other uses Apple does not normally permit.
The report pointed to earlier examples from the first years of iOS, when jailbroken phones could record video before Apple added that feature itself. Users also ran Android on iPhones, unlocked carrier restrictions, and installed themes. On current devices, a jailbroken iPhone can still install apps outside the App Store, browse the full file system, and remove preinstalled software.
Few users do that now. Even so, each working jailbreak on current hardware shows that Apple’s defenses can still be defeated.
Stage video showed root SSH access after reboot
Video from the event, posted by jailbreak researcher Billy Ellis, showed the team rebooting the phone, unlocking it with the regular passcode, and then opening an SSH session as root. Terminal output displayed iOS 27.0.1 and an uptime of about two minutes.
Hexacon is being held in Paris on October 16 and 17, so the demonstration took place on the conference’s opening day. The event is aimed at researchers who discover and exploit security flaws, and its talks usually focus on bugs in heavily used platforms, including phones and browsers.
Calif.io has not disclosed the bug chain
Calif.io has not said which vulnerabilities were used in the jailbreak, and there is no public tool available. In a newsletter post from the conference, the company listed four demos, including a Signal one-click and an iMessage demo, and said everything “will be released in due time.”
Getting root on a current iPhone usually requires a chain of bugs. The chain has to escape the app sandbox, take control of the kernel, and bypass hardware-backed protections such as Pointer Authentication Codes, which are designed to detect tampering with memory pointers. Making the jailbreak survive a reboot is harder because Apple verifies the code that runs during startup.
Earlier Calif.io posts mentioned Claude in Apple exploit research
In April, Calif’s Thai Duong wrote that Claude helped him break down an iOS Safari exploit in a series explaining how a real iPhone jailbreak works. In May, Calif said Anthropic’s Claude Mythos Preview helped it build a macOS kernel exploit against Apple M5 chip protections in under a week.
“We didn’t build the chain alone. Mythos Preview helped identify the bugs and assisted throughout exploit development,” he said.
Apple’s iOS 27 security notes, published on September 14, credited Calif.io “in collaboration with Claude and Anthropic Research” for two bugs that could let an app trigger a denial of service or a system crash. The notes did not connect either of those bugs to the jailbreak shown at Hexacon.
Apple has not publicly commented
A chain that gives root access on a fully updated iPhone is the same type of capability sold by commercial spyware vendors to governments. Apple typically patches such chains once it has the details. That means how long iOS 27.0.1 remains exposed may depend largely on when Calif decides to publish its findings.
As of Friday, Apple had not publicly commented on the demo. The company has said it does not confirm security issues until patches are available. Calif also has not said when it plans to release the technical details.