As promised, the iPhone Dev Team released an update to the UltraSn0w unlock for iOS 5 today. This update allows users with unlockable basebands running iOS 5 to unlock their iPhone 3GS, or iPhone 4.

This version of UltraSn0w (1.2.4) doesn’t add any new basebands to the compatibility list, but if you’re running basebands 4.26.08, 05.11.07, 05.12.01, 05.13.04, or 06.15.00 on the iPhone 3GS, or baseband 01.59.00 on the iPhone 4, then you can unlock your device right now…

If you’ve yet to update to iOS 5, but you have one of the aforementioned qualifying basebands, then you can use our RedSn0w tutorial for Mac, or our Sn0wBreeze tutorial for Windows, to update your iPhone to iOS 5 without updating your baseband.

Again, you must use one of the preservation methods listed above in order to keep your baseband unlockable.

Here are the release notes from the Dev Team regarding 3GS owners, and possible baseband downgrades in some special situations:

Note: there’s a special “trick” that iPhone3GS owners with baseband 06.15 need for iOS5. During the new setup screens you see when you start iOS5 for the first time, you’ll be asked about Location Services. Be sure to select “Disable Location Services” when asked! Later on in the setup, you’ll have the chance to turn on Location Services again when asked if you want to use “Find my iPhone”. It’s fine to turn it back on at that point, if that’s your desire (or you can always go in and enable it in Settings.app).

Also, some iPhone3GS users with the 06.15 baseband may have tried to install iOS5 using a stock IPSW (even though you should never ever try to use a stock IPSW if you’re an ultrasn0w unlocker). If you did try this, your baseband is probably in an inconsistent state, and you’ll need to reflash the 06.15 baseband again (using redsn0w). Be very careful if you use redsn0w to reflash the iPad baseband — don’t interrupt the process! And please avoid using stock IPSWs in the future 🙂 Unlockers should never go near stock IPSWs.

How to Unlock Your iPhone 3GS or iPhone 4 Using UltraSn0w 1.2.4:

Step 1: Verify your baseband is compatible by checking above.

Step 2: Update to iOS 5 using our RedSn0w baseband preservation tutorial or Sn0wBreeze baseband preservation tutorial.

Step 3: If you haven’t already,jJailbreak your device (tethered only for all iPhone users except 3GS old bootrom).

Step 4: Download and install UltraSn0w 1.2.4 from Cydia. (Gevey SIM users, see yesterday’s Gevey SIM post)

Step 5: Test out your unlock by attempting to use a SIM differing from your carrier SIM.

As mentioned, this latest release of UltraSn0w does not add any additional basebands to the compatibility list, so if you’re not on one of the basebands listed above, you will not be able to unlock with UltraSn0w.

If you do happen to qualify, however, head over to Cydia; your package awaits you.

Have you preserved your baseband for unlock? If so, please chime in below…