Fugu Jailbreak

Great news! There’s another jailbreak in the works, this time for iOS 13.3.1. Its called Fugu and, according to its creator, Linus Henze, it is “the first open-source jailbreak based on the checkm8 exploit.

fugu jailbreak

Interested? Then let’s dive in

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What is Fugu Jailbreak?

Until now, Checkra1n was the only jailbreak that used the checkm8 bootrom exploit, but that looks set to change with the announcement of the Fugu jailbreak tool. The checkm8 exploit is safe from being patched by Apple because it is a bootrom exploit, so its no surprise that developers are using it to base their tools on.


Before you get too excited, Fugu has not yet been released as a public jailbreak tool. The developer’s GitHub project page states that the jailbreak is in development and is really meant as a tool for developers. A package manager, such as Cydia or Sileo can be installed, most tweaks and other stuff simply won’t work.

And another warning

The developer ( Twitter ) makes it clear that “although the root filesystem is mounted read/write,” if you boot your device into a non-jailbreak mode, the root file system resets to stock. Right now, it looks like Fugu is nothing more than a tool that developers can use for research and testing. While installing Sileo/Cydia is possible, Cydia Substrate is absent, which means you cant run any tweaks or packages.

That’s not all

It also looks as if Fugu is quite limited compared to the Checkra1n jailbreak. For starters, it is only supported on the 2017 iPad Pro right now, and it can only be installed on that device using XCode and macOS so, right now, Fugu isn’t suitable for normal users.

We’re not done yet

The GitHub Fugu project page lists the four main components in the Fugu jailbreak tool:

  • Fugu – macOS app used for exploiting the iOS device using the Checkm8 exploit. It also uploads iDownload, iStrap, and iStrap Loader.
  • iStrap Loader – this is a small shellcode used to patch iBoot and then load iStrap
  • iStrap – this is a kernel bootstrapper, what shows up on your device when it is booting. This will patch the kernel and, if needed, inject the boot arguments, before injecting the shellcode into the kernel
  • iDownload – a small app installed on your device during boot and launches in place of launchd. It will fork itself, running launchd, with the fork listening on port 1337 and providing a simple interface similar to bash.

What do you think?

Clearly, Fugu isn’t ready for public release right now and is a long way behind the Checkra1n jailbreak. To that end, we wouldn’t recommend you attempt to use it, at least not at the moment. While this could change at any time in the future, right now, we suggest you treat Fugu as a development tool only. If you want to jailbreak your device and is compatible with the Checkm8 exploit, stick to using the Checkra1n jailbreak.

Over to you

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