If your Samsung Galaxy S26 Ultra is stuck on "Custom Binary Blocked by FRP Lock" or shows a DRK (Device Root Key) error, your phone has detected unofficial firmware or a modified boot image. This guide explains why this happens and how to fix it using Odin.
What Causes This Error?
The error appears when two conditions are met: 1) A non-stock binary is detected (TWRP, Magisk-patched AP, custom ROM). 2) FRP is active (Google account was synced before the flash).
The DRK error is Samsung's server-side verification that checks whether security certificates are intact. When Knox is tripped and DRK cannot verify, you get "DRK dm-verity verification failed."
Common triggers: Flashing Magisk AP with Google account synced, installing TWRP without removing Google account, flashing wrong model firmware, interrupted Odin flash, re-locking bootloader with modified partitions.
How to Fix — Flash Stock Firmware via Odin
What You Need
Windows PC, Samsung USB drivers, Odin 3.14.4+, original USB cable, stock firmware for your exact model and CSC.
Step 1: Download Correct Stock Firmware
Check model number on the blocked screen or retail box. Download matching firmware using Frija or SamFW. Extract the ZIP to get BL, AP, CP, CSC files.
Step 2: Boot into Download Mode
Hold Power + Volume Down for 10 seconds to force reboot. Immediately hold Volume Down + Volume Up and plug in USB cable. Press Volume Up to enter Download Mode.
Step 3: Flash with Odin
Open Odin. Verify device detected (blue/green ID:COM box). Load files:
- BL → BL_*.tar.md5
- AP → AP_*.tar.md5 (original, NOT Magisk-patched)
- CP → CP_*.tar.md5
- CSC → CSC_*.tar.md5 (NOT HOME_CSC — full reset required to clear FRP)
Options: check Auto Reboot and F. Reset Time. Do NOT check Re-Partition. Click Start. Wait for PASS! in green.
Step 4: Complete Setup
After reboot, complete initial setup. Since CSC was used (full reset), no FRP prompt should appear. The Custom Binary Blocked error is gone.
Fixing DRK Error
Follow the same stock firmware flash process. Note: Knox counter remains at 0x1 permanently. Samsung Knox features (Pay, Secure Folder, Pass) will not work even after restoring stock.
If DRK error persists on stock firmware, the EFS partition may be corrupted. EFS contains IMEI and security certificates. Repair requires a previously saved EFS backup or professional box tools (Z3X, Chimera, Medusa Pro).
Prevention
Before rooting/flashing: Remove Google account first (Settings → Accounts → Remove). Do a factory reset from Settings. Then proceed with custom flashing.
Always verify firmware: Match exact model number and CSC before flashing.
Back up EFS: Before bootloader unlock, save EFS partition using ADB root or recovery tools.
Troubleshooting
Odin does not detect: Reinstall USB drivers, try USB 2.0 port, different cable.
Odin shows FAIL: Re-download firmware, verify correct model.
FRP screen still appears: You used HOME_CSC instead of CSC. Reflash with CSC.
IMEI shows null: EFS corrupted. Requires professional box tool repair.
Guide by XDA Unlocker Team. Last updated: July 2026.