Fugu15 is a semi-untethered per assigned jailbreak for iOS 15.
It contains a code-signing bypass, kernel exploit, kernel PAC bypass, and PPL bypass.
Additionally, it can be installed via Safari, i.e. a computer is not required, except for a Web Server that hosts Fugu15.
Please note that Fugu15 does not support tweaks (no tweak injection library).

Tested Devices and iOS Versions

• iPhone Xs Max: iOS 15.4.1
• iPhone 11 (SRD): iOS 15.4.1
• iPhone 12 (SRD): iOS 15.4.1
• iPhone 12 Pro Max: iOS 15.4.1
• iPhone 13: iOS 15.1 (offline edition – see bugs below [WiFi bug])

Other devices are probably supported as well.
Non-arm64e devices are not supported.

Recommend Reading:

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Building

Prerequisites:

1. Make sure you have Xcode 13/14 14.1 installed
2. Import the fast path arm certificate (Exploits/fast path/arm.pfx) into your Keychain (double-click on the file). The password is “password” (without quotes)
3. You need a validly signed copy of Apple’s Developer App from the AppStore (with DRM!). Copy the IPA to Server/Orig.ipa. Note that if you would like to use a different AppStore App you will need to get its Team ID and add TEAMID=<the App's Team ID> to all make commands

Now you can simply run make to build Fugu15 (internet connection required to download dependencies).
Please note that you will be asked to grant “fastPathSign” access to the Keychain item “privateKey” (the private key of the fast path certificate). Enter your password and select “Always allow”.

Building Tools

Building Fugu15 requires multiple Tools which can be found in the Tools directory. Building them is entirely optional because I’ve already compiled them.
If you want to build them yourself, simply run make in the Tools directory.

Installing

There are two ways to install Fugu15 on your device: Via Safari or via USB

Installing via Safari

To install Fugu15 via Safari, do the following (requires you to own a domain):

1. Make sure your device is connected to the same network as your computer
2. Change the DNS A record for a domain you own to the local IP Address of your computer
3. Obtain a certificate for your domain (e.g. via Let’s Encrypt) and copy it to Server/serverCert/fullchain.cer (the certificate itself) and Server/serverCert/server.key (private key)
4. Make sure you have Flask installed (pip3 install Flask)
5. Change serverUrl in Server/server.py to your domain
6. Run python3 server.py in the Server directory
7. Visit https://<your domain> on your iPhone and follow the instructions

Recommend Reading:

#> How to Jailbreak iOS 15.5

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#> How to open the HEIC file – iPhone /iPad

#> TrollTools IPA for TrollStore with iOS 15 theming tools

Installing via USB

1. Install Fugu15_Developer.ipa, e.g. via ideviceinstaller -i Fugu15_Developer.ipa
2. Open the newly installed “Developer” App (or whatever AppStore App you used) on your iPhone

iDownload

Like all Fugu jailbreaks, Fugu15 ships with iDownload. The iDownload shell can be accessed on port 1337 (run iproxy 1337 1337 & and then nc 127.1 1337 to connect to iDownload).
Type help to see a list of supported commands.
The following commands are especially useful:

• r64/r32/r16/r8 <address>: Read a 64/32/16/8 bit integer at the given kernel address. Add the @S suffix to slide the given address or @P to read from a physical address.
• w64/w32/w16/w8 <address> <value>: Write the given 64/32/16/8 bit integer to the given kernel address. Also supports the suffixes described above and additionally @PPL to write to a PPL-protected address (see krwhelp).
• kcall <address> <up to 8 arguments>: Call the kernel function at the given address, passing up to 8 64-Bit integer arguments.
• tcload <path to TrustCache>: Load the given TrustCache into the kernel

Procursus Bootstrap and Sileo

Fugu15 also ships with the procursus bootstrap and Sileo. Run the bootstrap command in iDownload to install both. Afterwards, you might have to respring to force Sileo to show up on the Home Screen (uicache -r).

Procursus is installed into the /private/preboot/jb directory and /var/jb is a symlink to it.

Known Issues/Bugs

1. If oobPCI (the process exploiting the kernel) exits, the system might be left in an inconsistent state and panic at some point. This usually occurs about 5 seconds after running the exit_full command in iDownload.
   Workaround: Don’t quit oobPCI or make sure to do it as fast as possible to reduce the chance of a kernel panic. The reason for this panic is currently unknown.
2. When not connected to power, entering deep sleep will cause a kernel panic due to a bug in DriverKit (also happened with Fugu14). Unfortunately, the fix from Fugu14 does not work on iOS 15.
   Workaround: This bug will not occur when quitting oobPCI. However, the bug described above may occur when oobPCI exits.
3. Some iOS versions (at least iOS 15.1 and below, maybe 15.2 and 15.3 too) have a DriverKit bug that causes bus mastering to be disabled for the WiFi chip when running oobPCI, causing a kernel panic when WiFi is used. This bug can be fixed but a fix is not included in Fugu15 at the moment.
   Workaround: Disable WiFi.

FAQ

Q: I’m an end user. Is Fugu15 useful to me?
A: No.

Q: My iOS version/device is not supported by Fugu15, will you add support for it?
A: No. (I’m done with iOS 15)

Q: Will you ever add support for tweak injection?
A: No.

Q: Do you provide official support for Fugu15? Are any updates planned?
A: No.

Q: I installed/updated something through Sileo but it won’t launch. How can I fix that?
A: Fugu15 uses TrustCache injection to bypass code signing. Therefore, if you install or update something, it’s code signature must be in a TrustCache. You can load additional TrustCaches from the iDownload shell via the tcload command.

Q: Wen eta Fugu16??????
A: …