PS4/PS5 Mast1c0re exploit: PS4 10.50 confirmed, USB Elf loader released

Security research McCaulay Hudson has released updates to his implementation of the Mast1c0re exploit, slowly building a reasonable homebrew environment. People can run the exploit on the latest PS4 10.50 and PS5 6.50 (pending updates, it is likely PS5 7.00 will be compatible as well). Today’s release includes a ELF loader from USB.

What is the Mast1c0re exploit for PS4/PS5?

Mast1c0re is an unpatched vulnerability on PS4 and PS5, running through their PS2 emulation layer. The vulnerability was disclosed, and described with great detail, by PlayStation hacker CTurt in September last year, and a public reimplementation was released by McCaulay Hudson early 2023.

Some specific PS2 games for PS4/PS5 are vulnerable to buffer overflows, which allows us to run unsigned code on the PS4 and PS5. The currently only known exploitable game through this vulnerability is Okage: Shadow King, a PS2 game available for PS4 and PS5 on Sony’s PSN. By loading specifically crafted save files into this game, it is possible to trigger an exploit chain on PS4/PS5 running the most recent firmwares, to then enable some (limited) homebrew capability.

So far the most “user friendly” use cases for this vulnerability have been emulators, and PS2 Game ISOs.

PS4 10.50 Support for Mast1c0re confirmed

Mast1c0re works with the latest PS4 Firmware 10.50, as confirmed by McCaulay’s recent update of the repository. PS5 7.00 on the other hand, still seems to be pending confirmation.

Mast1c0re PS2 USB Game Loader

Until now it’s been possible to load PS2 Games from within the exploit, by sending them via a TCP connection. Although doable, it’s not necessarily the easiest way, and today McCaulay offers us a different way to load the games, via a USB stick. The USB stick needs to be formatted in exFAT, and have specific folders for the loader to work (see below).

Download and Install PS2 USB Game Loader

The PS2 USB Game Loader only works for PS4 at the moment. Specifically:

• PS4
  • 5.05
  • 6.72
  • 9.00
  • 10.01
  • 10.50

Notes:

• we have a basic explanation on how to setup and run the hack here. Be sure to replace the hello world file with the mast1c0re-ps2-network-elf-loader.
• Once the elf Loader is ready, send the USB Elf Loader to it. It should then be ready to load games from USB

From the Readme:

• Requires the mast1c0re-ps2-network-elf-loader game save to load the ELF file.
• The USB drive must be formatted with exFAT and MBR.
• The USB root directory should contain a folder named “Games” which contains a single folder for each game, containing a file ending in a “.iso” file extension, and optionally a “.conf” file.

Michael Crump has a video showcasing the USB Loader in action, although that’s for an earlier version that used FAT32 instead of ExFAT: