CVE-2026-21014 – CAN Bus Frame Replay Attack on Automotive ECU

Program Code (Python SocketCAN sim)

# can_replay_sim.py - Simulates CAN bus replay
import time

can_messages = []

def send_can(msg_id, data):
    print(f"CAN {msg_id:#x}: {data.hex()}")
    can_messages.append((msg_id, data))

def receive_can():
    return can_messages[-1] if can_messages else None

# Simulate car sending "door unlock" command
send_can(0x100, b'\x01\x00\x00\x00')  # unlock

# Attacker replays captured frame
time.sleep(1)
captured = receive_can()
if captured:
    print("Replaying captured frame...")
    send_can(captured[0], captured[1])

CVE-2026-21014 – CAN Bus Frame Replay Attack on Automotive ECU

Overview

An automotive Controller Area Network (CAN) does not implement message authentication or freshness checks. An attacker with physical access to the OBD‑II port can capture a legitimate frame (e.g., unlock door) and replay it later to perform unauthorized actions.

Vulnerability Details

• Type: Replay Attack
• Impact: Unauthorized vehicle control.
• Root Cause: CAN protocol lacks inherent security; messages have no timestamps, counters, or MACs.

Exploit Demonstration

Run the simulation:

python can_replay_sim.py

The script prints the capture and replay of an unlock command.