An issue was discovered on Brother MFC-J491DW C1806180757 devices. The printers web-interface password hash can be retrieved without authentication, because the response header of any failed login attempt returns an incomplete authorization cookie. The value of the authorization cookie is the MD5 hash of the password in hexadecimal. An attacker can easily derive the true MD5 hash from this, and use offline cracking attacks to obtain administrative access to the device.
Weakness
During installation, installed file permissions are set to allow anyone to modify those files.
Potential Mitigations
- Compartmentalize the system to have “safe” areas where trust boundaries can be unambiguously drawn. Do not allow sensitive data to go outside of the trust boundary and always be careful when interfacing with a compartment outside of the safe area.
- Ensure that appropriate compartmentalization is built into the system design, and the compartmentalization allows for and reinforces privilege separation functionality. Architects and designers should rely on the principle of least privilege to decide the appropriate time to use privileges and the time to drop privileges.
References