Just a minute ago, @iH8Sn0w released an updated version of Sn0wbreeze 2.4 Beta 1,
which not only supports iOS 4.3.1 Jailbreak, it also support Ultrasn0w for the following basebands only (01.59.00 / 04.26.08 / 05.11.07 / 05.12.01 / 05.13.04 / 06.15.00). Keep in mind this is not a Untethered Jailbreak. The Dev Team’s are working on untethered jailbreak for iOS 4.3 / iOS 4.3.1 and is expected to be released soon. For those who can’t wait, you use Sn0wbreeze 2.4b1 (Tethered Jailbreak), which can jailbreak all iOS device (iPhone 4, iPhone 3GS, iPodTouch 4G, iPodTouch 3G, iPad) running iOS 4.3.
Sn0wbreeze 2.4b1 – Details
Step 1: Download the required files – Links posted at the bottom of the postHow To Jailbreak & Unlock iPhone 4 & iPhone 3GS Running iOS 4.3 Using Sn0wbreeze 2.4b1
Step 2: Launch Sn0wbreeze 2.4 BETA 1 and Click Ok on the disclaimer.
Step 3: Click Next – Blue Arrow in the bottom right corner
Step 4: Click on Browse, Navigate to the Original iOS 4.3.1 Firmware and Click Open
Step 5: Let it verify the IPSW file. Once Verified Click Next
Step 6: Now, click on Expert Mode (Selecting Baseband Prservation Mode will only preserve your iPhone baseband. It will not Jailbreak your iPhone)
Step 7: Now, Click on General and then click on Next
Step 8: Check mark, Activate The iPhone to hacktivate your iPhone (Do this if you don’t have your SIM) , Check mark Install SSH and then Click Next.
Step 9: Now, If you want to add any custom packages add them here. If not, just click Next
Step 10: Now, Click on Build IPSW and Click Next to cook custom firmware.
Note: By now, Snowbreeze should create custom cooked IPSW file for your device. And you will also notice a iBooty Folder for iOS 4.3. You need this to tethered boot into your iOS device.
Step 11: Once the custom firmware is cooked, Connect your iOS device and turn it OFF.
Step 12: Now, follow the on screen instructions to put your iOS device in PWNED DFU mode.
Step 13: Once your iOS device in PWNED DFU mode, Launch iTunes
Step 14: Hold down SHIFT KEY and Click on Restore on iTunes, Navigate to the custom cooked IPSW file, which should be saved on your desktop, and click on Open.
Step 15: Now, just sit and relax, iTunes will take care of the rest.