*June 2024 | By AI Secure Tech Blog*

Introduction

In the age of smart and connected vehicles, secure communications aren't just about Wi-Fi or Bluetooth — even the wires between your truck and trailer can be a target. A recently disclosed vulnerability, CVE-2022-26131, highlights a little-known but critical weakness in a product many truck operators depend on: the Power Line Communications PLC4TRUCKS J2497 Trailer Receiver.

This device, designed to save wiring and simplify communications by sending signals over standard trailer cables, turns out to be susceptible to a surprisingly simple attack: remote radio frequency (RF) injection.

This post will break down the bug, demonstrate the workings with code snippets, and walk you through an example exploit scenario, all in plain and simple language.

What Is PLC4TRUCKS J2497?

First, let's quickly explain what this device does. The J2497 Power Line Carrier (PLC) standard allows trucks and trailers to share digital signals — like ABS status, brake commands, or diagnostics — using the physical wiring that's already there (normally, the stop lamp circuit).

PLC4TRUCKS is a commercial implementation of this. Their J2497 trailer receiver "listens" to digital signals modulated on top of existing power lines, and acts on them (e.g. lighting up warning lamps or adjusting systems in the trailer).

According to the official CVE entry

> _"PLC4TRUCKS J2497 trailer receivers are susceptible to remote RF induced signals, allowing unauthorized command injection or disruption of communications over power line interfaces."_

Put simply: A hacker with the right radio gear could sit outside your truck and inject fake signals without ever touching your vehicle.

How? It turns out the J2497 receiver, when designed without proper shielding and filtering, can "hear" in-band radio interference — even from short distances. A crafty attacker can use a radio transmitter, tune it to the right frequency, and make your trailer system believe it's receiving legitimate commands.

Let's walk through the steps an attacker might take

1. Sniff the Protocol: The attacker needs to know the digital format J2497 uses (a public standard, see here).
2. Build a Signal Generator: The attacker creates a digital-to-analog modulation circuit that produces the correct J2497 waveform.
3. RF Inject: Using a strong amplifier and antenna next to the trailer harness, they transmit the crafted signal, inducing voltage in the trailer's wiring.
4. Receiver Confusion: The poorly shielded or filtered receiver can't tell it's not coming from the tractor, so it parses and acts on those messages.

Real-World Example

An attacker in a parked vehicle near a truck stop could send "ABS Fault" or "Diagnostic Request" commands — causing warning lights, system resets, or even hampering legitimate troubleshooting.

Code Snippet: Generating the J2497 Modulation

The J2497 encodes bits using Frequency Shift Keying (FSK) at 115.2 kbps, with 5V swing on the stop lamp wire.

Here's sample Python code using PySDR (with a suitable SDR-RF frontend like HackRF or PlutoSDR) to generate a valid J2497-like FSK waveform:


import numpy as np
from scipy import signal
import matplotlib.pyplot as plt

FS = 2e6  # Sample rate
F_MARK = 133333  # Hz, J2497 Mark frequency
F_SPACE = 116666  # Hz, J2497 Space frequency
DURATION = .01 # seconds
BITS = '101010101111000'  # Example message

def generate_fsk(bits, fs, f_mark, f_space, baud=115200):
    samples = np.array([])
    samples_per_bit = int(fs / baud)
    for b in bits:
        f = f_mark if b == '1' else f_space
        t = np.arange(samples_per_bit) / fs
        samples = np.concatenate([samples, np.sin(2 * np.pi * f * t)])
    return samples

fsk_signal = generate_fsk(BITS, FS, F_MARK, F_SPACE)
plt.plot(fsk_signal[:100])  # Plot a small part
plt.title('J2497 FSK Example')
plt.show()

You could feed this waveform (after amplification) into a simple software-defined radio transmitter, and if your signal is strong enough and close enough, the vulnerable receiver will pick it up.

Exploit Scenario

Goal: Trigger a dashboard warning in the target truck.

Steps

1. Prepare the waveform, encoding a "Diagnostic Trouble Code" or "ABS Fault" message following the J2497 frame format.
2. Transmit the waveform from your SDR at the right frequency and power, antenna placed near the target trailer wiring.
3. The susceptible PLC receiver will pick up the signal and forward it to the in-cab dashboard, potentially confusing the operator.

Warning: This is for educational purposes only! Unlawful interference with vehicle communications is a crime.

References and Further Reading

- NIST NVD: CVE-2022-26131
- SAE J2497 Power Line Communications Standard
- DEF CON 30 Talk: Hacking Trucks with Powerline
- PySDR: Software Defined Radio in Python

Filtering: Upgrade receiver modules with bandpass or common-mode filters to block external RF.

- Firmware Updates: Require message authentication (hard with J2497, but possible with higher-level protocols).

Fleet operators and vehicle OEMs should audit all power line communication components in use — vulnerable setups should be repaired or replaced.

Conclusion

CVE-2022-26131 is a clear reminder that attackers can target the most unlikely parts of your vehicle — including the wires meant for your lights and brakes. Simple RF attacks can disrupt or fake trailer communications if systems are not properly hardened. If you use PLC4TRUCKS J2497 receivers, assess your exposure and upgrade your defenses now.

Stay safe out there on the road!

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Timeline

Published on: 03/10/2022 17:47:00 UTC
Last modified on: 03/23/2022 18:37:00 UTC