After recently releasing their jailbreak for iOS 4.3.1 via PwnageTool and RedSn0w, the Dev Team is now getting ready to unleash their UltraSn0w unlock.

The current 4.3.1-compatible UltraSn0w is currently being tested by a few beta testers, and according to a tweet by Dev Team front man MuscleNerd, if everything goes well, UltraSn0w should be released tonight…

That’s the good news. The bad news is it is not going to work with any baseband. Just like the previous version of UltraSn0w, this one will only work with iPhone 3GS and iPhone 4 on basebands 01.59.00, 04.26.08, 05.11.07, 05.12.01, 05.13.04, and 06.15.00.

So to be clear, if your baseband is different from those above, you will not be able to unlock. If you are currently on one of these basebands but on a previous firmware, update using PwnageTool, which will bring you up to 4.3.1 while preserving the baseband.

We will of course update the blog as the news fall.