CVE-2019-20457
📋 TL;DR
This vulnerability allows unauthenticated attackers to retrieve the MD5 hash of the printer's web interface password through failed login attempts. Attackers can then crack this hash offline to gain administrative access to affected Brother printers. All Brother MFC-J491DW devices with firmware version C1806180757 are affected.
💻 Affected Systems
- Brother MFC-J491DW
⚠️ Manual Verification Required
This CVE does not have specific version information in our database, so automatic vulnerability detection cannot determine if your system is affected.
Why? The CVE database entry doesn't specify which versions are vulnerable (no version ranges provided by the vendor/NVD).
🔒 Custom verification scripts are available for registered users. Sign up free to download automated test scripts.
- Review the CVE details at NVD
- Check vendor security advisories for your specific version
- Test if the vulnerability is exploitable in your environment
- Consider updating to the latest version as a precaution
⚠️ Risk & Real-World Impact
Worst Case
Full administrative compromise of the printer, allowing attackers to intercept print jobs, modify device settings, install malicious firmware, or use the device as a network pivot point.
Likely Case
Unauthorized administrative access to the printer's web interface, enabling attackers to view print history, change network settings, or disable security features.
If Mitigated
Limited impact if printers are isolated on internal networks with strict firewall rules and strong administrative passwords that resist MD5 cracking.
🎯 Exploit Status
Exploitation requires only HTTP requests to the printer's web interface. Attackers can retrieve the password hash from failed login response headers and then crack it offline using rainbow tables or brute force.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check Brother support for latest firmware
Vendor Advisory: https://support.brother.com/g/s/security/en/index.html
Restart Required: Yes
Instructions:
1. Visit Brother support website. 2. Download latest firmware for MFC-J491DW. 3. Upload firmware via printer web interface. 4. Reboot printer after installation.
🔧 Temporary Workarounds
Disable web interface
allTurn off the printer's web interface if not needed
Access printer settings > Network > Web Services > Disable
Network segmentation
allIsolate printers on separate VLAN with strict firewall rules
🧯 If You Can't Patch
- Change administrative password to a strong, complex password that resists MD5 rainbow table attacks
- Implement network access controls to restrict access to printer management interface to authorized IPs only
🔍 How to Verify
Check if Vulnerable:
Send a failed login request to the printer's web interface and check if the response contains an Authorization cookie with MD5 hash value.Check Version:
Access printer web interface > Settings > Device Information > Firmware VersionVerify Fix Applied:
After patching, verify that failed login attempts no longer return password hash in response headers.📡 Detection & Monitoring
Log Indicators:
- Multiple failed login attempts from single IP
- Successful admin login from unusual IP after failed attempts
Network Indicators:
- HTTP requests to printer web interface from external IPs
- Unusual traffic patterns to printer management port
SIEM Query:
source_ip=* AND dest_port=80 AND uri_path="/admin/login" AND http_status=401