iOS 4.3.1 Already Jailbroken, Baseband Still Locked
Rising to the occasion, iOS hackers have already managed to jailbreak the updated iOS 4.3.1 which dropped earlier this afternoon.
For now, the best solution is still a tethered jailbreak, but what do you really expect in such a short amount of time? After gathering all the required utilities, you’ll build a custom firmware image, place your phone in DFU mode, and then use iTunes to “restore” your phone with the modified firmware.
Since this is a tethered jailbreak, you’ll still have to put the phone back into DFU mode and run the boot utility from your computer after every time your iPhone resets. Currently the jailbreak is only working on iPhone 4 models, but look for a 3GS version in the near future.
While this process is safe for putting iOS 4.3.1 on an iPhone running older software, if you’ve already installed the update, your baseband has been updated as well, locking the phone against carrier changes. If you want to use your phone off-network, be sure to modify the 4.3.1 firmware for the jailbreak before it touches your phone. For full details on the process, check out the guide at Redmond Pie.
Source: Redmond Pie