CVE-2023-0851: Canon MF642Cdw Buffer Overflow Vulnerability

CVE-2023-0851 Overview

CVE-2023-0851 is a critical buffer overflow vulnerability affecting the CPCA (Canon Printing Communication Architecture) Resource Download process in Canon Office and Small Office Multifunction Printers and Laser Printers. This vulnerability allows an attacker positioned on the same network segment to send specially crafted data that overflows internal memory buffers, potentially causing the affected device to become unresponsive or enabling arbitrary code execution on the printer's embedded system.

The vulnerability affects a wide range of Canon printer product lines sold globally, including the Satera, Color imageCLASS, and i-SENSYS series across Japan, United States, and Europe markets. Firmware versions 11.04 and earlier are confirmed vulnerable, representing a significant attack surface in enterprise and small office environments.

Critical Impact

Network-accessible buffer overflow enabling remote code execution without authentication on Canon multifunction printers and laser printers across multiple product lines globally.

Affected Products

• Canon Satera LBP660C Series/LBP620C Series/MF740C Series/MF640C Series (Japan) - Firmware Ver.11.04 and earlier
• Canon Color imageCLASS LBP660C Series/LBP620C Series/X LBP1127C/MF740C Series/MF640C Series/X MF1127C (US) - Firmware Ver.11.04 and earlier
• Canon i-SENSYS LBP660C Series/LBP620C Series/MF740C Series/MF640C Series, C1127P, C1127iF, C1127i (Europe) - Firmware Ver.11.04 and earlier

Discovery Timeline

• 2023-05-11 - CVE-2023-0851 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2023-0851

Vulnerability Analysis

The CPCA Resource Download process is a core component of Canon printer firmware responsible for handling network-based resource transfers and configuration updates. The buffer overflow occurs when the CPCA handler fails to properly validate the size of incoming data before copying it into a fixed-size memory buffer. This allows an attacker to supply data exceeding the expected buffer boundaries, corrupting adjacent memory regions.

This vulnerability is classified under CWE-122 (Heap-based Buffer Overflow) and CWE-787 (Out-of-bounds Write), indicating that the overflow occurs in dynamically allocated memory regions. The heap-based nature of this vulnerability is particularly concerning as it can lead to arbitrary memory corruption, potentially allowing attackers to overwrite function pointers, heap metadata, or other critical data structures used by the printer's embedded operating system.

The attack can be launched remotely from any system on the same network segment without requiring authentication or user interaction. Successful exploitation could grant attackers complete control over the printer device, enabling them to intercept print jobs containing sensitive information, use the compromised printer as a pivot point for lateral movement within the network, or render the device permanently inoperable.

Root Cause

The root cause of this vulnerability is improper input validation in the CPCA Resource Download process. The firmware fails to verify that incoming data lengths do not exceed the allocated buffer sizes before performing memory copy operations. This classic buffer overflow pattern results from missing bounds checking, allowing attackers to write data beyond the intended memory boundaries and corrupt heap memory structures.

Attack Vector

The attack vector is network-based, requiring the attacker to have access to the same network segment as the vulnerable printer. The attacker crafts malicious network packets targeting the CPCA Resource Download service and sends them to the printer's network interface. Since no authentication is required and no user interaction is needed, the attack can be executed entirely remotely by any device that can reach the printer on the network. The exploitation complexity is considered low, making this vulnerability accessible to attackers with moderate technical skills.

The attack flow involves identifying vulnerable Canon printers on the network, crafting oversized payloads targeting the CPCA Resource Download process, and transmitting the malicious data to trigger the buffer overflow condition. Depending on the attacker's payload construction, this can result in denial of service through device crash or arbitrary code execution through memory corruption techniques such as heap spraying or return-oriented programming.

Detection Methods for CVE-2023-0851

Indicators of Compromise

• Unexpected printer reboots or unresponsive states without apparent cause
• Anomalous network traffic patterns to Canon printers, particularly unusual data volumes to CPCA-related services
• Print job failures or corruption coinciding with network anomalies
• Unexpected firmware modifications or configuration changes on affected devices

Detection Strategies

• Implement network traffic analysis to detect oversized or malformed packets destined for Canon printer network services
• Deploy intrusion detection system (IDS) rules to monitor for buffer overflow exploitation patterns targeting printer protocols
• Enable logging on network infrastructure to capture connection attempts to vulnerable printer models
• Conduct regular firmware version audits across all Canon printer assets to identify devices running vulnerable firmware versions

Monitoring Recommendations

• Monitor printer device health through SNMP or vendor management tools for unexpected state changes
• Establish baseline network traffic patterns for printers and alert on deviations
• Implement network segmentation monitoring to detect lateral movement attempts originating from printer subnets
• Review printer access logs and configuration change records for unauthorized modifications

How to Mitigate CVE-2023-0851

Immediate Actions Required

• Identify all Canon printer models and firmware versions in your environment against the affected product list
• Apply network segmentation to isolate printers from general user networks where possible
• Restrict network access to printer management interfaces using firewall rules or access control lists
• Prioritize firmware updates for printers exposed to untrusted network segments

Patch Information

Canon has released firmware updates to address this vulnerability. Organizations should consult the official Canon security advisories for their specific regions:

• Canon Japan Vulnerability Response
• Canon PSIRT Advisory CP2023-001
• Canon Europe Security News
• Canon USA Service Notice

Firmware updates beyond version 11.04 should remediate this vulnerability. Organizations should download the appropriate firmware from Canon's official support channels and follow the documented update procedures for each printer model.

Workarounds

• Implement strict network segmentation to place printers on isolated VLANs with controlled access
• Configure firewall rules to restrict printer access to only authorized management workstations and print servers
• Disable unused network services and protocols on affected printers if configuration options permit
• Consider temporarily disconnecting vulnerable printers from the network until firmware updates can be applied in high-risk environments

# Example firewall rule to restrict printer access (adjust IPs and ports as needed)
# Allow print traffic only from authorized print server
iptables -A FORWARD -d 192.168.10.0/24 -s 192.168.1.100 -p tcp --dport 9100 -j ACCEPT
iptables -A FORWARD -d 192.168.10.0/24 -s 192.168.1.100 -p tcp --dport 631 -j ACCEPT
# Block all other traffic to printer subnet
iptables -A FORWARD -d 192.168.10.0/24 -j DROP