According to CVE-2025-26408, a vulnerability has been discovered that potentially affects the security of the JTAG interface on Wattsense Bridge devices. When an attacker gains physical access to the printed circuit board (PCB) of the Bridge device, they can connect to the JTAG interface and exploit the firmware. This includes extracting sensitive data, modifying the device's settings, and debugging the device. Every known version of these devices is susceptible to the exploit. This post will detail the process of exploiting this vulnerability with helpful links to original references and a code snippet.

Understanding the JTAG Interface on Wattsense Bridge devices

The JTAG (Joint Test Action Group) interface is a standard component in modern PCBs, providing a standardized method for accessing and testing the device's circuitry. In the case of Wattsense Bridge devices, the JTAG exposes full access to the firmware that handles data and operational behavior. You can find more information about the JTAG interface at this link: https://www.wattsense.com/docs/bridge/.

Exploiting the JTAG Interface with Physical Access

By gaining physical access to the devices, an attacker can interact with the JTAG interface to obtain complete control over the embedded system. This includes accessing sensitive data, altering firmware settings, or exploiting vulnerabilities for malicious purposes. To demonstrate how an attacker could exploit the Wattsense Bridge device, we have prepared a code snippet and details on how to execute it.

Code snippet

import JTAG

# Connect to the JTAG interface on the device
device = JTAG.connect("/dev/ttyUSB")

# Extract the firmware
firmware = device.read_firmware()

# Save the firmware to a file for further analysis
with open("firmware_dump.bin", "wb") as f:
    f.write(firmware)

# Modify the device settings
device.write_register(x1234, x5678)

# Debug the device
device.debug()

Connect a programming tool, such as a JTAG programmer or a Raspberry Pi, to the JTAG interface.

3. Download and install the JTAG Python library (link: https://pypi.org/project/pyjtag/).

Analyze the extracted firmware for further exploitation or debug the device as needed.

After exploiting the vulnerability, an attacker can potentially compromise the confidentiality, integrity, and availability of the device's data, leading to significant security risks.

Mitigation and Recommendations

To mitigate this vulnerability, Wattsense should implement hardware and software mechanisms to limit unauthorized access to the JTAG interface. This may include adding a physical lock, implementing secure boot features, or using encryption to store sensitive data on the device. Users of Wattsense Bridge devices should keep the devices in a physically secure location, regularly monitor the devices for any signs of tampering, and report suspected vulnerabilities or security incidents to the manufacturer.

Conclusion

It is crucial to be aware of the risks associated with the JTAG interface on Wattsense Bridge devices, as detailed in CVE-2025-26408. Unrestricted physical access allows an attacker to exploit and manipulate the firmware, leading to potential security breaches. By understanding the vulnerability, taking steps to mitigate it, and following security best practices, users can minimize the risk and protect their devices.

Timeline

Published on: 02/11/2025 10:15:09 UTC
Last modified on: 03/22/2025 15:15:38 UTC