Sony is relatively open towards the third-party Android development community and ships all its devices with an unlockable bootloader. However, in the United States, the company had to give in to the wishes of T-Mobile and Verizon and release the Xperia Z3 with a locked down bootloader.
A locked bootloader makes it significantly tougher for developers and advanced users to gain root access on the handset. Since the bootloader cannot be unlocked, developers must find an exploit that allows them to gain root privileges.
A few months after the release of T-Mobile’s Xperia Z3 and Verizon’s Xperia Z3V, developer zxz0O0 has found an exploit in the latest firmware on both handsets. Using the tool created by the developer, Xperia Z3/Z3v owners can achieve proper root access on their handset.
Gaining root access will allow owners of these handset to remove all the bloat that was pre-loaded by Verizon and T-Mobile on the handset. In addition, they can install and use Xposed framework along with its modules to enjoy all the customisation benefits offered by a custom ROM without actually flashing any ROM on it.
Since root access is gained via an exploit, it is likely that T-Mobile and Verizon will patch it with a future firmware update. So, Xperia Z3 and Z3v owners are recommended not to accept any software updates from their carrier until it is confirmed that they can gain root access on it as well.
The download link of the tool and the rooting steps can be found here.