[Research / Guide] Recovering the AX7501-B0 to Official Stock Firmware (UART, CFE, UBIFS Analysis)

yan220

Hi everyone,

I wanted to share a technical case study and research notes on restoring a second-hand Zyxel AX7501-B0 back to official stock Zyxel firmware (V5.17(ABPC.8)C0) after acquiring a unit locked down with custom ISP firmware (V5.17(ABWW.5)C0).

In this specific state, local management interfaces were inaccessible and standard upgrade utilities were unavailable. The write-up documents the full troubleshooting process from a hardware and low-level firmware perspective

The full write-up, technical notes, and details are published on GitHub:
https://github.com/RunVard/Zyxel-ISP-unlock

⚠️ Important Disclaimer: Before attempting any hardware modifications or firmware flashing, verify with your ISP that the device is customer-owned and not rented, loaned, or leased. Modifying ISP property may violate your service terms or incur replacement penalties. Perform all procedures at your own risk.