CVE-2026-1789: Printer Management Information Disclosure

CVE-2026-1789 Overview

A vulnerability exists in the browser-based remote management interface of certain Canon production printers and office/small office multifunction printers. This security flaw allows an authenticated administrator to access sensitive information on the device via crafted requests, potentially exposing confidential configuration data, credentials, or other sensitive information stored on the affected devices.

Critical Impact

Authenticated administrators can leverage crafted requests to the remote management interface to extract sensitive device information that should otherwise be restricted.

Affected Products

• Canon Production Printers
• Canon Office Multifunction Printers
• Canon Small Office Multifunction Printers

Discovery Timeline

• 2026-04-24 - CVE-2026-1789 published to NVD
• 2026-04-24 - Last updated in NVD database

Technical Details for CVE-2026-1789

Vulnerability Analysis

This vulnerability is classified under CWE-807 (Reliance on Untrusted Inputs in a Security Decision). The browser-based remote management interface fails to properly validate or sanitize administrative requests, allowing privileged users to craft specific requests that bypass normal access controls and retrieve sensitive information from the device.

The vulnerability requires network access and high privileges (administrator authentication) to exploit. While this limits the attack surface to authenticated administrators, it presents a significant risk in environments where administrative credentials may be compromised or where insider threats are a concern. The confidentiality impact is high as attackers can access sensitive device information, though integrity and availability remain unaffected.

Root Cause

The root cause stems from the remote management interface's reliance on untrusted inputs when making security decisions. The web interface does not adequately validate administrative requests, allowing crafted inputs to access information beyond the intended scope. This improper input validation in the security decision logic enables information disclosure to authenticated users.

Attack Vector

The attack is conducted over the network through the browser-based remote management interface. An attacker must first authenticate as an administrator to the device's web management portal. Once authenticated, the attacker can craft specific HTTP requests to the management interface that exploit the improper validation logic, causing the device to return sensitive information that should be protected.

The attack does not require user interaction beyond the initial authentication and can be executed with low complexity once administrative access is obtained. Organizations with weak administrative password policies or compromised credentials face elevated risk from this vulnerability.

Detection Methods for CVE-2026-1789

Indicators of Compromise

• Unusual or unexpected HTTP requests to the printer's remote management interface from authenticated administrator sessions
• Anomalous access patterns to device configuration endpoints or sensitive information retrieval operations
• Unexpected data extraction or exfiltration from printer management interfaces
• Administrative access from unexpected IP addresses or during unusual hours

Detection Strategies

• Monitor web server logs on affected Canon printers for unusual request patterns from authenticated administrator sessions
• Implement network-level monitoring to detect abnormal traffic to printer management interfaces
• Deploy intrusion detection signatures targeting crafted requests to Canon printer web interfaces
• Correlate administrative login events with subsequent request patterns to identify potential exploitation attempts

Monitoring Recommendations

• Enable comprehensive logging on all Canon printer remote management interfaces
• Configure SIEM alerts for anomalous administrative access patterns to print devices
• Regularly audit administrative accounts and their access patterns on affected devices
• Monitor for large data transfers from printer management interfaces that may indicate information extraction

How to Mitigate CVE-2026-1789

Immediate Actions Required

• Review and restrict administrative access to affected Canon printers to only essential personnel
• Implement strong authentication policies for printer administrator accounts
• Place printer management interfaces on isolated network segments with restricted access
• Audit current administrative accounts and remove unnecessary privileges

Patch Information

Canon has released security advisories and mitigation guidance for this vulnerability. Organizations should consult the following resources for firmware updates and patching information:

• Canon Vulnerability Response Notice
• Canon PSIRT Advisory CP2026-003
• Canon Europe Product Security Info
• Canon CPA2026-003 Mitigation Guide

Organizations should apply available firmware updates from Canon as soon as possible and follow the vendor's mitigation guidance.

Workarounds

• Restrict network access to printer management interfaces using firewall rules and access control lists
• Implement multi-factor authentication for administrative access where supported
• Place affected printers on isolated VLANs with restricted access from untrusted network segments
• Disable remote management interfaces when not actively required for administration
• Implement strict password policies for all printer administrative accounts

# Network isolation example using firewall rules
# Restrict access to printer management interface (example port 443)
# Allow only from trusted management network

iptables -A INPUT -p tcp --dport 443 -s 10.10.10.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP