In summary, if you are looking at a device with a baseband newer than 3.07.07, the . For those collectors or enthusiasts holding a device still on this version, it remains a "holy grail" of sorts for software-based carrier freedom on legacy Apple hardware.
Apple patched the vulnerabilities in the AT+XAPP command processing and other memory overflow bugs that allowed unauthorized carrier signaling. 3d7e7a9bpnach patched
Most carriers now unlock iPhone 4 devices for free upon request, rendering "unpatched" basebands unnecessary. In summary, if you are looking at a
For most iPhone 4 users, once the baseband was updated to a patched version (like those found in iOS 6 or 7), it became impossible to return to 3.07.07 because the baseband has its own "one-way" fuse-based or SHSH-verified update mechanism. Current Status and Legacy Most carriers now unlock iPhone 4 devices for
Modern iterations of this baseband use stricter cryptographic signing, preventing users from "downgrading" to the vulnerable 3.07.07 version once they have updated to a newer, patched version.
In the early 2010s, iPhone users often sought "software unlocks" to use their devices on different carriers without official authorization. The baseband is the subsystem of the phone that manages cellular functions.