If the software is completely corrupted, you will need the full installer. Here is how to acquire it legally and safely: 1. EFI Sales Portal / Download Center

Navigate to: Utilities → Reset Module → Full Factory Reset . Confirm the warning message. The process takes 2–5 minutes.

The Canon EOS Utility is the official way to manage settings and download images from a PC, but it generally does not include service-level "EFI" reset functions.

Complete Guide to EOS EFI Software: Reset, Download, and Installation