Hackers Demonstrate Reboot-Resistant iPhone 18 Pro Jailbreak

Preface

At Hexacon, a security conference in Paris, security firm Calif.io demonstrated an untethered jailbreak on an iPhone 18 Pro running iOS 27.0.1. The onstage demonstration showed the phone rebooting and then returning to a state with root access, without being connected to a computer. The result drew attention because an untethered jailbreak must persist across a restart, a more demanding test than a temporary compromise. Calif has not disclosed the vulnerabilities behind the demonstration or released a public tool, saying it will publish details later. Apple’s iOS 27 security notes separately credit Calif.io, working with Claude and Anthropic Research, for two bugs that could cause a denial of service or system crash; the notes do not connect those bugs to the jailbreak. The demonstration is evidence of a security capability, but its technical details and practical availability remain undisclosed.

Lazy bag

Calif.io showed an iPhone 18 Pro running iOS 27.0.1 regain root access after a reboot at Hexacon in Paris on October 16, 2026. An untethered jailbreak removes restrictions and remains active after restarting, but the firm has not identified the vulnerabilities or released a tool. Apple has not publicly commented on the stage demo. Its published security notes credit Calif.io, Claude and Anthropic Research for two unrelated crash bugs, with no indication that either bug was used in this jailbreak. The key uncertainty is how long the latest iOS version may remain exposed before Calif publishes details and Apple can assess or address the flaws.

Main Body

Security firm Calif.io demonstrated an untethered jailbreak on an iPhone 18 Pro running iOS 27.0.1 at Hexacon, an offensive security conference in Paris. The demonstration took place on Friday, October 16, 2026, the opening day of the conference, which runs October 16 and 17. The team showed the device rebooting and then returning to a state in which it had root access. The event’s audience includes researchers who discover and exploit security flaws, and its talks commonly address vulnerabilities in widely used platforms, including phones and browsers.

A jailbreak removes some of the software restrictions Apple applies to iPhones. Apple’s approach uses signed code, an app sandbox and a protected startup chain to limit what software can run and what users can change. A successful jailbreak can grant root access, the highest level of control over the operating system. Depending on the method and the device, that access can enable users to install software Apple has not approved, customize the interface, browse the full file system, remove preinstalled applications and alter other parts of the system.

The term “untethered” describes a jailbreak that returns after the device restarts without needing to be connected to a computer or manually re-exploited. That distinction matters because some jailbreaks only work temporarily or must be reactivated after every reboot. The Calif.io demonstration appeared to show persistence across a restart: the phone was rebooted, unlocked with its regular passcode and then accessed through an SSH session running as root.

Video from the stage, posted by jailbreak researcher Billy Ellis, showed the sequence. The terminal output identified iOS 27.0.1 and displayed an uptime of about two minutes. The clip provides a visible indication that the device had restarted and that a root-level session was available afterward. However, a short video cannot disclose the full exploit chain, establish how widely the method works, or confirm whether the technique is reliable across other devices and configurations.

Jailbreaking has historically enabled capabilities that Apple later incorporated into iOS or that remain outside its intended system. In the early years of iOS, users with jailbroken devices could record video before Apple added that feature. Some also ran Android on iPhones, unlocked carriers, installed themes and used other unofficial modifications. Today, a jailbreak may allow installation of apps outside the App Store, access to the complete file system or removal of unwanted built-in software. These examples illustrate why users may find the practice appealing, but they do not establish that the Calif.io demonstration has been made available for public use.

Jailbreaking also carries risks. Changes to system protections can make a device less secure or stable, interfere with updates and expose data to malicious software. A public exploit may be useful to researchers and technically experienced users, but similar capabilities can also be valuable to attackers. The demonstration therefore has significance beyond customization: it shows that a complex security boundary may have been crossed on a current device, while leaving the scope and potential consequences unclear.

Obtaining root access on a current iPhone generally requires a chain of vulnerabilities rather than a single simple flaw. A typical chain may need to escape the app sandbox, compromise the kernel and overcome hardware-backed protections. One example is Pointer Authentication Codes, which are designed to detect tampering with memory pointers. Each layer can prevent or complicate a different step of an attack. A method that reaches root must account for several defenses, making the details of the exploit chain important to understanding both its severity and the measures Apple may need to take.

Persistence across a reboot adds another challenge. During startup, Apple checks the software involved in loading the operating system. A jailbreak that remains active after restarting must therefore overcome or work around protections that are relevant to the startup process, not simply gain temporary control while the phone is already running. Calif.io has not explained how its demonstration achieved persistence, so it is not possible to assess the precise technique, the number of vulnerabilities involved or the conditions under which the result can be reproduced.

The firm has not named the vulnerabilities it used and has not released a public jailbreak tool. A Calif.io newsletter post from the conference listed four demonstrations, including a Signal one-click demonstration and an iMessage demonstration, and said everything “will be released in due time.” That statement indicates an intention to publish material later, but it does not provide a date or specify whether publication will include working tools, technical descriptions or both. Until more information is available, users and security teams cannot independently verify the exploit chain or determine whether the demonstrated method can be reproduced.

The timing of any disclosure may affect how long iOS 27.0.1 remains exposed. Once Apple has enough information to understand a vulnerability, it can investigate and prepare a security response. Apple typically patches exploit chains after learning the details, but the firm has not publicly commented on this demonstration. Apple’s stated practice is not to confirm security issues until patches are available. Calif.io has likewise not said when it will publish its findings, leaving the status of the underlying flaws uncertain.

Apple’s iOS 27 security notes, published September 14, credit Calif.io “in collaboration with Claude and Anthropic Research” for two bugs. Those bugs could let an app cause a denial of service or a system crash. The notes do not say either issue was part of the iPhone jailbreak, and the demonstrated root access should not be attributed to them without evidence. Keeping the findings separate is important: a crash bug can affect availability, while a jailbreak chain that grants root access can involve a different set of vulnerabilities and a substantially different level of control.

Calif.io has also discussed the use of AI tools in security research. In April, Calif’s Thai Duong wrote that Claude helped him analyze an iOS Safari exploit as part of a series explaining how an iPhone jailbreak works. In May, Calif said Anthropic’s Claude Mythos Preview helped it build a macOS kernel exploit against Apple’s M5 chip protections in under a week. Duong said, “We didn’t build the chain alone. Mythos Preview helped identify the bugs and assisted throughout exploit development.” These statements describe earlier research and the role the firm says AI assistance played; they do not establish that the same tools or methods were used in the iPhone 18 Pro demonstration.

A chain that provides root access on a fully updated iPhone is the kind of capability associated with commercial spyware vendors that sell tools to governments. That comparison concerns the potential power of the capability, not proof that Calif.io’s demonstration was used for surveillance or that a public exploit exists. Security researchers, device manufacturers and users need technical details to judge the actual risk. Until those details are released, the demonstration establishes that a notable result was shown on stage, while leaving questions about exploitability, affected devices and remediation unanswered.

For now, the most concrete facts are limited: Calif.io demonstrated an untethered jailbreak on an iPhone 18 Pro running iOS 27.0.1; the phone rebooted and regained root access; no vulnerabilities have been named; no public tool has been released; and Apple has not commented publicly on the demo. The next significant developments will be Calif.io’s disclosure and any security updates or statements from Apple. Those steps will clarify whether the demonstration reflects a broadly applicable vulnerability chain, a narrower research result or a combination of conditions that are difficult to reproduce.

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