3GS 4.2.1 Jailbreak Help

[lauren_869]

My jailbroken 3GS recently died while under warranty and Apple gave me a new one (3GS with firmware 4.2.1). I just want to know if there is any way to downgrade (without shsh blobs) or jailbreak with the current firmware? I did try researching this myself but I got a bit confused.

I'd really appreciate the help,
Lauren

[Simon]

There is now way to downgrade without SHSH. You can jailbreak with redsnow 0.9.6rc8 but it may be tethered depending on what bootrom it has.

[i.Annie]

Yep just find out that bootrom version. If it is old, it will be untethered and you can go ahead and jb. If it is new, consider if you can deal with a tethered jb or wait till a new jb is released.