iOS Internals · Inside iOS · Lesson 4 of 5

Updates & Jailbreaks

Learn why updates matter, how long iPhones get them, and what a jailbreak breaks.

Why updates matter

No software is perfect. Researchers, criminals and spyware companies all hunt for vulnerabilities, mistakes in code that let someone do what they shouldn't. When Apple fixes one, the fix arrives in an update. Apple says keeping your software up to date is one of the most important things you can do for your device's security.

Timing matters. Once an update is out, the fix itself can hint at where the hole was, so attackers race to use it against phones that haven't updated yet. Apple also doesn't discuss security problems publicly until it has investigated and a fix is available.

How long does an iPhone get updates? Apple doesn't publish an end date for every model. In a filing required by UK law, it committed to at least five years of security updates for the iPhone 15 Pro Max, counted from its launch in September 2023. In practice support often runs longer. iOS 27, released in 2026, supports the iPhone 11 and later, and the iPhone 11 came out in 2019. Apple sometimes ships security fixes for older iOS versions for a while too, but it has said that only the newest version gets every known fix. (In 2025 Apple switched to year-based numbers, jumping from iOS 18 to iOS 26.)

Not every fix waits for a full update. Starting with iOS 26.1, Apple can send Background Security Improvements, small security patches for parts like Safari and WebKit, the engine that displays web pages, between regular updates. They follow Apple's earlier quick-fix system, Rapid Security Responses, which began with iOS 16. To make sure they install, go to Settings, Privacy & Security, Background Security Improvements and check that Automatically Install is on.

For regular updates, go to Settings, General, Software Update and turn on Automatic Updates. Once you install an iOS update, you can't go back to the older version, so a fixed hole stays fixed.

Jailbreaks and an unfixable bug

A jailbreak removes the restrictions iOS puts on an iPhone. It gives the owner, or a tool they run, root access, the all-powerful administrator level that ordinary apps never get. People do it to run apps that Apple hasn't signed or to change parts of iOS that are normally locked.

Look back at what you've learned in this course. A jailbreak works by switching off or getting around the very protections that keep you safe:

• Code signing stops being enforced, so unsigned and tampered code can run.
• Sandbox rules can be loosened, so an app with root access can reach other apps' containers.
• Apps installed from outside the App Store skip App Review and notarization.

Apple's support page on unauthorized changes to iOS warns that they can expose personal information to attackers, cause crashes and battery drain, disrupt services like iCloud and iMessage, and stop future updates from installing. Many banking apps also refuse to run on jailbroken phones.

Jailbreaks depend on security bugs, and Apple patches those bugs in updates, so public jailbreaks usually work only on older iOS versions. One famous exception came in 2019. A researcher published checkm8, a bug in the Boot ROM of Apple's A5 to A11 chips, which covers iPhones from the 4S to the iPhone 8 and iPhone X.

Remember the weakness from module 1. The Boot ROM is read-only, so Apple couldn't patch it with an update. Fixing it took new chips, and from the A12 (iPhone XS and later) the bug is gone. checkm8 has real limits, though. It needs the phone in hand and connected by cable, and researchers reported that its effects don't survive a restart. Forensic tools have used it to examine older iPhones.

The safest choice for most people is simple. Don't jailbreak, keep updating, and replace an iPhone once it stops getting updates.