A major security investigation has uncovered eight critical vulnerabilities affecting hundreds of printer models from leading manufacturers, with the most severe flaw allowing attackers to remotely generate administrator passwords.

## Scope of the Problem

Rapid7 researchers discovered that 689 Brother printer models, along with 53 additional models from Fujifilm, Toshiba, and Konica Minolta, contain a fundamental security weakness that cannot be fixed through firmware updates alone.

## The Critical Vulnerability (CVE-2024-51978)

The most dangerous flaw involves predictable password generation. During manufacturing, these printers create default administrator passwords using a flawed algorithm based on the device’s serial number. The process follows these steps:

– Takes the first 16 characters of the serial number
– Adds 8 bytes from a static “salt” table
– Creates a SHA256 hash
– Converts to Base64 encoding
– Uses the first eight characters with some letter substitutions

Attackers can easily reverse this process. They can obtain a printer’s serial number through various methods, then use the algorithm to generate the admin password and gain full control of the device.

## Additional Security Flaws

The research uncovered seven other vulnerabilities ranging from medium to high severity:

– **Information leakage** – Attackers can access sensitive data without authentication
– **Buffer overflow** – Authenticated attackers can trigger system crashes
– **Forced connections** – Devices can be manipulated to open unauthorized network connections
– **Remote crashes** – Printers can be disabled remotely
– **Credential theft** – Admin access allows harvesting of stored passwords

## Impact and Risk

These vulnerabilities can be combined to:
– Take complete control of affected printers
– Execute malicious code remotely
– Access stored documents and address books
– Use compromised devices to attack other network systems
– Steal credentials for external services

## The Fix Challenge

While manufacturers have released firmware updates addressing most issues, CVE-2024-51978 presents a unique problem. Since the flaw exists in the manufacturing process itself, any printer made before the discovery will remain vulnerable unless users manually change the default password.

Brother has confirmed this vulnerability “cannot be fully remediated in firmware” and requires changes to their manufacturing process for new devices.

## Immediate Actions Required

Users with affected printers should:

1. **Change default admin passwords immediately**
2. **Apply all available firmware updates**
3. **Restrict admin interface access over unsecured networks**
4. **Limit external network exposure**

## Manufacturer Response

All affected manufacturers – Brother, Konica Minolta, Fujifilm, Ricoh, and Toshiba – have published security bulletins with specific instructions for their customers. The disclosure process began in May 2024, with coordination assistance from JPCERT/CC.

This discovery highlights the critical importance of secure manufacturing processes and the challenges of fixing hardware-level security flaws in deployed devices.