689 Brother Printer Models Have an Unfixable Security Flaw — Is Yours on the List?

This is the biggest printer security story of 2026 so far, and it affects millions of devices worldwide.

In early February 2026, security researchers at Rapid7 disclosed eight vulnerabilities affecting 689 Brother printer, scanner, and label maker models — plus dozens of models from Fujifilm, Ricoh, Konica Minolta, and Toshiba that share the same underlying platform.

The worst part? Brother says the most critical flaw cannot be fully fixed through firmware updates.

The Core Problem: Your Serial Number IS Your Password

The most critical vulnerability (CVE-2024-51978) is embarrassingly simple:

Brother printers generate the default admin password directly from the device's serial number.

That means anyone who can see or guess your printer's serial number — which is typically printed on a label on the device itself — can calculate the admin password and gain full administrative access to the printer.

Why Can't Brother Fix This?

Because the password generation algorithm is baked into the manufacturing process. Fixing it would require changing how every printer generates its initial credentials — which means new hardware, not just a firmware update.

Brother can (and has) released firmware that mitigates the issue by: - Prompting users to change the default password on first setup - Adding warnings about default credentials

But the underlying flaw — that the default password is derived from the serial number — remains in every affected device.

The Full Vulnerability List

Rapid7 found eight vulnerabilities total, six of which require no authentication:

The unauthenticated firmware update capability (CVE-2024-51981) is particularly terrifying — an attacker could push malicious firmware to your printer without needing any credentials at all.

Are You Affected?

689 Brother models are affected, spanning: - HL series (laser printers) - DCP series (digital copier/printers) - MFC series (multifunction centers) - TD/QL series (label printers) - ADS series (scanners)

Also affected: 46 Fujifilm models, 5 Ricoh models, 6 Konica Minolta models, and 2 Toshiba models that use Brother's engine.

The most popular affected models include many in the Brother HL-L2300/2350 series, MFC-L2700/2750 series, and MFC-9330 series — these are some of the best-selling small office printers in the United States.

What to Do Right Now

Step 1: Change the Admin Password (Do This Today)

Even though the default password generation is flawed, changing it to a strong, unique password eliminates the primary attack vector. Here's how:

1. Open a web browser and type your printer's IP address
2. Log in with the current admin credentials
3. Navigate to Administrator → Login Password
4. Set a strong password (12+ characters, mixed case, numbers, symbols)
5. Write it down and store it securely (not on a sticky note on the printer)

Step 2: Update Firmware

Brother has released patches that address several of the other vulnerabilities. Check for updates at support.brother.com for your specific model.

Step 3: Disable Unnecessary Network Services

Turn off: - SNMP v1/v2 (addresses CVE-2024-51982) - Any remote management you don't actively use - FTP and Telnet services

Step 4: Network Segmentation

Put your Brother printer on an isolated network segment. Even if the printer is compromised, proper segmentation prevents the attacker from reaching your workstations and servers.

Step 5: Cover or Remove the Serial Number Label

This sounds low-tech, but if the serial number is the key to the default password, don't leave it visible. Place a label over the serial number sticker (after you've recorded it for warranty purposes).

The Bigger Lesson

This vulnerability highlights a fundamental problem with printer security: manufacturers treat security as an afterthought.

The decision to derive admin passwords from serial numbers was a convenience feature — it made initial setup easier. But convenience and security are almost always in tension, and when manufacturers choose convenience, it's the customer who pays the price.

This is why we always recommend that businesses treat printer setup as a security configuration exercise, not just a "plug it in and print" task. Every printer that joins your network should go through a security hardening checklist before it prints its first page.

For broader IT security guidance on protecting your business from vulnerabilities like these, Wisetechy Solutions offers comprehensive security assessments that include every device on your network — including the ones most people forget about, like printers.

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Worried about your Brother printer? Valley Printer Pros can check your specific model, update your firmware, change default credentials, and configure proper network segmentation. We've been helping San Fernando Valley businesses secure their printers since day one.

Call us at (818) 574-8240 — don't wait until your printer becomes someone else's access point.

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Sources: Rapid7 Research Disclosure, SecurityWeek, Dark Reading, Tom's Hardware, Security Magazine, Brother Security Advisory