CVE-2024-51978: Authentication Bypass Vulnerability

CVE-2024-51978 Overview

CVE-2024-51978 is a critical authentication bypass vulnerability affecting Brother printers and related OEM devices from Konica Minolta and Toshiba Tec. An unauthenticated attacker who knows the target device's serial number can generate the default administrator password for the device. This vulnerability can be chained with CVE-2024-51977 to first discover the target device's serial number via HTTP/HTTPS/IPP, PJL requests, or SNMP queries, enabling complete unauthenticated administrative access to affected printers.

Critical Impact

Attackers can gain full administrative control over vulnerable printers by deriving default credentials from easily obtainable serial numbers, potentially compromising enterprise print infrastructure and enabling lateral movement within networks.

Affected Products

• Brother Printers (689+ models reported affected)
• Konica Minolta OEM devices (see Konica Minolta Security Advisory KM-2025-0001)
• Toshiba Tec OEM devices (see Toshiba Tec Security Information)

Discovery Timeline

• 2025-06-25 - CVE-2024-51978 published to NVD
• 2025-07-25 - Last updated in NVD database

Technical Details for CVE-2024-51978

Vulnerability Analysis

This vulnerability stems from the use of a weak default credential mechanism (CWE-1391: Use of Weak Credentials) in Brother printer firmware. The default administrator password for affected devices is algorithmically derived from the device's serial number, which creates a predictable authentication mechanism. Since serial numbers can be obtained without authentication through multiple network protocols (HTTP/HTTPS/IPP, PJL, or SNMP), this effectively transforms a supposedly secure default password into a trivially bypassable authentication control.

The attack chain typically involves first exploiting CVE-2024-51977 to retrieve the target device's serial number, then using that serial number to compute the default administrator password. Once authenticated, attackers gain complete control over the printer's configuration and capabilities.

Root Cause

The vulnerability exists due to improper default credential generation in Brother printer firmware. Rather than implementing truly random or device-specific credentials that cannot be derived from public information, the firmware uses the device serial number as input to a deterministic algorithm that generates the default administrator password. This design flaw means that any attacker who can obtain the serial number—which is exposed through multiple unauthenticated interfaces—can compute the administrative credentials.

Attack Vector

The attack is network-based and requires no authentication or user interaction. An attacker on the same network segment (or with network access to the printer) can:

1. Query the target printer's serial number using HTTP/HTTPS requests to the web interface, IPP (Internet Printing Protocol), PJL (Printer Job Language) commands, or SNMP queries
2. Apply the known algorithm to derive the default administrator password from the serial number
3. Authenticate to the printer's administrative interface with full privileges

The exploitation process has been documented in public research, with a Nuclei template available for automated detection and a Metasploit module under development. See the Rapid7 Blog on Brother Vulnerabilities and the Brother Vulnerabilities Repository for technical details on the exploitation mechanism.

Detection Methods for CVE-2024-51978

Indicators of Compromise

• Unexpected administrative login attempts to printer web interfaces, particularly from non-administrative workstations
• SNMP queries targeting printer OID values associated with serial number retrieval
• PJL commands requesting device information including @PJL INFO ID or similar device identification queries
• IPP requests querying printer attributes related to device identification
• Web interface requests to pages that expose serial number information

Detection Strategies

• Monitor network traffic for serial number enumeration patterns across multiple printers in rapid succession
• Alert on administrative authentication to printers from previously unknown IP addresses
• Implement network segmentation monitoring to detect unauthorized access to printer VLANs
• Deploy honeypot printers configured to alert on any administrative login attempts
• Scan the Nuclei Template for CVE-2024-51978 against your environment to identify vulnerable devices

Monitoring Recommendations

• Enable and centralize printer audit logs where supported by firmware
• Monitor for configuration changes on network printers, especially to network settings, authentication policies, and firmware update configurations
• Implement SNMP community string rotation and monitoring for unauthorized SNMP access
• Consider network-based anomaly detection for unusual printer communication patterns

How to Mitigate CVE-2024-51978

Immediate Actions Required

• Change the default administrator password on all Brother, Konica Minolta, and Toshiba Tec printers immediately to a strong, unique password not derived from the serial number
• Restrict network access to printer administrative interfaces using firewall rules or network segmentation
• Disable unnecessary protocols (SNMP, PJL over network) where not required for operations
• Implement printer access controls limiting which hosts can communicate with printers
• Audit printer configurations for unauthorized changes

Patch Information

Brother, Konica Minolta, and Toshiba Tec have released security advisories addressing this vulnerability. Organizations should consult the following vendor resources for device-specific firmware updates and mitigation guidance:

• Brother Support FAQ #00100846
• Brother Support FAQ #00100848
• Brother Support FAQ #00100620
• Konica Minolta Security Advisory KM-2025-0001
• Toshiba Tec Security Information

Note: Some reports indicate certain older models may not receive firmware patches. For these devices, implementing the workarounds below is critical.

Workarounds

• Immediately change all default administrator passwords to strong, unique credentials
• Place all printers on isolated VLANs with restricted access from the corporate network
• Block direct internet access to printers and restrict management access to designated administrative workstations
• Disable SNMP v1/v2c and use SNMPv3 with authentication where SNMP is required
• Disable unused network services including IPP, PJL over network, and web interfaces where possible

# Network segmentation example - restrict printer access via firewall
# Allow only print traffic (TCP 9100, IPP 631) from authorized subnets
# Block all management traffic (HTTP/HTTPS 80/443) except from admin VLAN

# Example iptables rules for a printer gateway
iptables -A FORWARD -d 10.10.50.0/24 -p tcp --dport 9100 -s 10.10.0.0/16 -j ACCEPT
iptables -A FORWARD -d 10.10.50.0/24 -p tcp --dport 631 -s 10.10.0.0/16 -j ACCEPT
iptables -A FORWARD -d 10.10.50.0/24 -p tcp --dport 443 -s 10.10.100.0/24 -j ACCEPT
iptables -A FORWARD -d 10.10.50.0/24 -j DROP