Is there an Ultrasn0w unlock for iPhone 4 Baseband 4.11.08 or 4.12.01?
Unfortunately, there hasn’t been any ultrasn0w unlock for iPhone 4 since baseband 1.59.00 which was the first baseband versionreleased for iPhone 4.
However, baseband 2.10.04, 3.10.01 and 4.10.01 can be unlocked using SIM interposer device such as Gevey SIM.
Sherif_Hashim, a prominent baseband hacker, admitted that there was a huge roadblock when he attempted to unlock it early this year. What’s this “roadblock”? No one knows for sure.
The new baseband 4.12.01 that comes with iOS 5.1 is probably has less vulnerabilities and may be even more difficult to unlock.