Pixel 6 series can’t go back to Android 12 after updating to Android 13 due to security vulnerability [U]

Ben Schoon | Aug 16 2022 - 10:40 am PT

Google released Android 13 today for Pixel devices, and it’s rolling out now to devices. However, for Pixel 6 series owners, Android 13 is essentially a permanent upgrade, as there’s no way to roll back to Android 12.

Android updates are generally reversible, with the ability to install an older version by manually sideloading the update. This always requires resetting your phone and losing your data, but it’s a process that can be done.

With Android 13, however, Pixel 6, Pixel 6 Pro, and Pixel 6a are left unable to downgrade back to Android 12 builds. Google noted on the site where it hosts Factory Images that users will not be able to move back to Android 12 after installing this new version.

Warning: The Android 13 update for Pixel 6, Pixel 6 Pro, and the Pixel 6a contains a bootloader update that increments the anti-roll back version. After flashing an Android 13 build on these devices you will not be able to flash older Android 12 builds.

This is an unusual move on Google’s part, but the reason for the change is a new bootloader update that “increments the anti-roll back version.” Google has implemented this security measure in Android for several years now, generally to prevent exploits from older software versions from being implemented on devices.

Update 8/16: Google has confirmed the reason why Pixel 6, Pro, and Pixel 6a can’t revert back to Android 12. Mentioned within the Android Flash Tool, Google says that the bootloader version used previously had a security vulnerability, as was first spotted by security researcher @flawedworld (and highlighted by Mishaal Rahman).

Google’s warning reads:

WARNING – If this is FLASHED you CANNOT go back to an old Android build
Your device is running a vulnerable version of the bootloader. After flashing this build your device’s anti-roll back counter will be incremented to prevent previous vulnerable versions of the bootloader from being flashed on the device in the future. This will prevent flashing existing Android 12 releases.

This generally won’t be an issue for most users, but it’s interesting nonetheless. Given the devices it affects, it seems reasonable to assume this might have something to do with Google Tensor. In any case, just know that upgrading to Android 13 on a Pixel 6 series device is effectively permanent.