What’s CardUnlock?

It’s a homebrew utility that requires taiHEN or (thankfully, as you’ll see) HENkaku. This homebrew works by mouting the card used with a higher FW to another mount point and killing off id.dat on it; that way you can use the card on a 3.60 Vita!

That’s great but how are you going to access the card? If you have a Vita Slim or a PSTV, it’s easy; simply remove your existing memory card, run taiHEN without a memory card installed, install the homebrew and viola! You can unlock any card you wish (you don’t have to reboot to do it).
Source

GitHub link (source code + full instructions)

Download link