CVE-2022-29586 is a high-severity vulnerability found in certain Konica Minolta bizhub Multifunction Printer (MFP) devices that were shipped before April 14, 2022. This flaw allows an attacker to escape the device’s secure sandbox/kiosk mode—just by using a regular USB keyboard and pressing a single key. In this long-read post, we’ll break down what this vulnerability is, step-by-step details on how the exploit works, important code snippets and official references, and offer exclusive insight into its implications for office security.

Understanding The Vulnerability

Many modern MFP devices from Konica Minolta provide a kiosk mode. This mode limits what users can do—a necessity for public-facing or shared printers. The security model assumes users only interact with the touchscreen interface, with no direct way to break out of the locked "sandbox".

However, researchers discovered that the underlying system listened for certain keyboard events even in restricted mode. Specifically, by plugging in a generic USB keyboard and pressing the F12 key, an attacker could exit the kiosk environment and access broader device or even system-level functions!

Why Is This Dangerous?

- Bypassing Vending/Payment Features: Users could print or copy without payment or authentication.

Access to Configurations: Settings that are meant to be protected could be altered.

- Network Privilege Escalation: If the device is integrated with the local network, it could become an entrypoint for wider attacks.

Exploit Details: Step-by-Step Walkthrough

The exploit is shockingly simple and requires no software skills—just a USB keyboard and physical access to the device. Here’s how it works:

Approach the MFP and locate a free USB-A port (commonly on the side or beneath the touchscreen).

2. Plug in any standard USB keyboard. Most office MFPs don’t disable USB input, for ease of maintenance.

Press the F12 key on the keyboard.

5. The kiosk/sandbox restrictions are lifted. You now have access beyond what the device owner intended!

How It Works (under the hood)

The device’s software is built on top of a standard Linux/embedded OS. Keyboard events are read from /dev/input/event* and forwarded to a handler. While the UI is restricted in kiosk mode, it did not filter or ignore special keys such as F12. Pressing F12 was mapped to an "exit" or "developer menu" action that immediately bypasses the lock.

Code & Configuration Snippet (Illustrative)

While device firmware is proprietary, the problem can be shown by looking at how many embedded systems are set up:

# Pseudocode based on likely firmware structure

def handle_key_event(event):
    if event.key_code == 'F12':
        if kiosk_mode:
            # EXIT KIOSK MODE (VULNERABILITY)
            exit_kiosk()
        else:
            pass # normal handling

# The bug: No authentication or confirmation, just exits on F12

A better approach would be

def handle_key_event(event):
    if event.key_code == 'F12' and kiosk_mode:
        if user_is_admin():
            exit_kiosk()
        else:
            log_attempt()
            show_error("Admin only!")

- NIST NVD Entry for CVE-2022-29586
- Konica Minolta Security Advisory (April 2022)
- Exploit Database Writeup (CVE-2022-29586) (if available)
- Rosesec List Thread - Sandbox Escape Walkthrough

Exclusive Insight: Why Physical Attacks Still Matter

Even as cybersecurity focus shifts to remote and network-based threats, physical attacks remain powerful and often overlooked. This vulnerability is a classic example of how a simple hardware action can undo all software protections. In busy office environments, it’s easy for someone to quickly plug in a keyboard and perform the escape in seconds flat—and most users or IT staff wouldn’t even notice.

If you use Konica Minolta bizhub printers manufactured before April 14, 2022

- Upgrade Firmware Immediately: Konica Minolta released a patched firmware that blocks F12 and similar keys in kiosk mode.

Conclusion

CVE-2022-29586 is a reminder: even secure hardware can be undone by overlooked input methods. Always patch, monitor, and physically secure your critical office hardware. If you manage public or high-security MFPs, block unused USB ports and keep firmware up-to-date.

Stay safe!

*For more security news, follow US-CERT and the Konica Minolta support page. If you suspect exploitation of this CVE, contact your security team now!*

Timeline

Published on: 05/16/2022 06:15:00 UTC
Last modified on: 05/26/2022 14:46:00 UTC