With the release of iOS 5.1 last week, Apple not only effectively broke exploits that were used in Redsn0w (for A4 Devices), Corona (A4 Devices) and Absinthe (for iPad 2 and iPhone 4S) jailbreak tools, but also wiped out the software unlock for the iPhone 3GS and the iPhone 4, known as Ultrasn0w.
Although it may not be a big deal for some people, for those users who use their iPhone on multiple networks, the firmware update does bring some inconvenience. Upgrading to iOS 5.1 would also update the device's baseband, taking out the effectiveness of the Ultrasn0w unlock tool.
In a recent update, the iPhone Dev Team warned users not to update blindly to iOS 5.1. The team advised users to use a custom IPSW to get to 5.1, if they require an Ultrasn0w unlock on their device.
In the same blog post, the iPhone Dev Team also announced that Ultrasn0w itself would be updated to 5.1 in the next few days. The promised update will definitely be a great relief for unlockers, but it won't bring any added baseband support.
According to Redmond Pie, the update will allow unlocking only on devices and basebands which are currently offered by the 1.2.5 version of the tool. The currently supported baseband models include 01.59.00, 04.26.08, 05.11.07, 05.13.01, 05.12.01 and 06.15.00. Users can check this by going to Settings > General > About > Modem Firmware.
However, for those users who can wait until the Dev Team gets the latest release out for the public, a developer known as zmaster has something to offer.
The developer has released a temporary fix on his own repository that goes by the name Ultrasn0w Fixer. The package is an interim fix for Ultrasn0w. The owners of devices running iOS 5.1 can install the package and then install the current version of Ultrasn0w to get the required unlock as long as the device and baseband are supported.
Users must note that the device has to be jailbroken on iOS 5.1 using custom firmware with the old baseband preserved. For more information on how to jailbreak iOS 5.1 (tethered) using Redsn0w, click here.
How to Use Ultrasn0w Fixer
Step 1: Since Ultrasn0w Fixer is not in a default repo, users need to add it. To do this, launch Cydia, select Manage from the tool bar at the bottom and then select Source from the ensuing list.
Step 2: Tap on Edit and then Add.
Step 3: Now enter the repository URL - http://repo.iparelhos.com and hit Add Source.
Step 4: After the repo is done loading, search Cydia for Ultrasn0w Fixer. Locate it and install it like a usual package.
Step 5: Once the Fixer package is complete, install the latest version of Ultrasn0w (1.2.5). Since it is in a default repo, you need to search for it in Cydia.