Firmware version and downgrade protection

Hi there,

I'm currently working on the firmware versioning and the downgrade protection for an nRF5340 with NCS 2.6.0.

The firmware consists of:

App Core
|-- build
|-- McuBoot
|-- TFM
--- B0

Net Core
--- B0n

I currently have a specific prj.conf file for the main application, the McuBoot and the HCI_IPC.

The version number is set in the "Version" file according to Zephyr.

The main prj.conf file has the following enabled:

# Downgrade Protection

I far as I understand from here, these are the only settings I have to take, in order that the downgrade prevention is active and they should be passed on to the sub-images like B0 and McuBoot.

However, I can up- and downgrade with the application "Device Manager" and "nRF Connect" for Android as much as I want without any protection.

Is there something else to consider?

Kind regards,


  • Hi Patrick,

    Did you test with different firmware versions by setting the application frirmware version as desribed here and the MCUBoot veersion by adjusting CONFIG_MCUBOOT_HW_DOWNGRADE_PREVENTION_COUNTER_VALUE? And if you do, is it MCUboot downgrade protection that does not seem to work or application downgrade prevention? Can you elaborate on how you test?

  • Dear Einar,

    I defined the application firmware version with the VERSION file to lets say 9.8.7. Built the firmware and flashed it to the nRF5340.

    I then reduced the number of the version to lets say 8.8.7 as well as a change in a blinky timer (for visual testing) and built the firmware. Loaded the app_update.bin to the smartphone and performed a DFU with either the "Device Manager" or "nRF Connect" application.

    The same test was performed with setting the CONFIG_MCUBOOT_IMGTOOL_SIGN_VERSION to similar values as described above.

    Other settings in the prj.conf were not changed.

    Loading the new application with a lower version number and booting from it was possible, without any issue. Same as loading and booting the higher version again.

    In regards to the CONFIG_MCUBOOT_HW_DOWNGRADE_PREVENTION_COUNTER_VALUE, do I understand that correctly, that the value defines the version number of the McuBoot?

    Kind regards,


  • Hi Patrick.

    I don't see any issues in this description, but the feature should work and I have not seen any other reports of problems with downgrade protection. Can you upload a project you use to test along with exact instructions for each step you take so that I can attempt to reproudce on my end?