The official Android 4.4.2 KitKat XXUCNG1 firmware for Galaxy S4 Mini I9190 can gain root access by performing these steps using ChainFire Auto-Root and ODIN flash tool.

Prerequisites:

1. Create a manual backup of all data files and personal settings stored on Galaxy S4 Mini I9190.

2. Battery level must be at least 50 per cent to avoid power interruption during the installation.

3. Enable USB debugging mode on the Galaxy S4 Mini smartphone.

4. Download and install the necessary USB drivers for the handset on the computer.

5. Download ChainFire's Auto-Root tool for Android 4.4.2 KitKat to the computer.

6. Download the ODIN flash tool to the computer.

Warning: We are not responsible for any errors which may occur on the Galaxy S4 Mini. Read and follow the instructions carefully to avoid damaging the device. Root access will also trip the Samsung Knox and remove any active warranty. Do this at your own risk.

Gaining Root Access:

1. Extract the ODIN flash tool executable file and ChainFire's Auto-Root to an easy access location on the computer.

2. Turn off the Galaxy S4 Mini then reboot it into Download Mode. Press and hole the volume down, home and power keys at the same time till the Android logo appears.

3. Launch the ODIN flash tool executable file on the computer.

4. Connect the smartphone using a USB cable. The ID:COM should flash yellow if the device has been detected. Otherwise, install the necessary USB drivers as mentioned above.

5. On the ODIN flash tool, click on PDA then select the file "CF-Auto-Root-serrano3g-serrano3gub-gti9190.tar.md5".

6. Check the AUTO REBOOT and F.RESET TIME on the ODIN flash tool.

7. Hit the START button to begin the rooting process.

8. During the rooting process, the smartphone will reboot automatically into Recovery Mode to install the necessary files.

9. Once the installation process has been completed, it should reboot automatically which may take up to five minutes before reaching the home screen.

10. After the device has reached the home screen, it can now be disconnected from the computer.

11. Check the root access status of the device by downloading the Root Checked app at the Google Play Store.

Troubleshooting:

In some cases, the device won't reboot automatically into Recovery Mode which prevents the root installation process.

- Remove the battery unit then reinsert it back and redo the entire process but leave the AUTO REBOOT option unchecked on the ODIN flash tool this time.

- Manually reboot the device into Recovery Mode. Remove the battery then reinsert it back, press and hold the volume up, home and power keys at the same time to proceed into Recovery Mode.

For bugs and issues, kindly send your feedback to the Team Android official Galaxy S4 Mini rooting page.