CVE-2025-3078: Printer Passback Information Disclosure

CVE-2025-3078 Overview

CVE-2025-3078 is a passback vulnerability affecting Canon production printers, office multifunction printers, small office multifunction printers, and laser printers. The flaw allows an authenticated attacker with administrative privileges to reconfigure external authentication service endpoints (such as LDAP or SMTP servers) to a host they control. Once a legitimate user or service authenticates through the printer, the stored credentials are sent to the attacker-controlled destination in cleartext or reversible form. Canon disclosed the issue in advisory CP2025-004 and classified it under CWE-522 (Insufficiently Protected Credentials).

Critical Impact
An administrator-level attacker can harvest LDAP, SMTP, or Active Directory credentials stored on affected Canon printers, enabling lateral movement into directory and email infrastructure.

Affected Products

Canon production printers covered by advisory CP2025-004
Canon office and small office multifunction printers (MFPs)
Canon laser printers identified in the Canon PSIRT Advisory CP2025-004

Discovery Timeline

2025-05-20 - CVE-2025-3078 published to the National Vulnerability Database
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-3078

Vulnerability Analysis

The issue is a credential passback (also called credential relay or LDAP passback) weakness in the device administration interface. Canon multifunction printers integrate with enterprise services such as LDAP, SMB, FTP, Kerberos, and SMTP, and they store the credentials used to bind to those services. The administrative interface allows changing the target server address for these integrations without re-prompting for the stored secret. An attacker with administrator access can repoint the server field to an attacker-controlled host, trigger an authentication test, and receive the cleartext credentials. Because printers commonly bind to directory services with privileged service accounts, harvested credentials often provide direct access to Active Directory, mail relays, or file shares.

Root Cause

The root cause aligns with CWE-522: credentials stored for outbound service authentication are not bound to the originally configured destination. The device replays the stored secret whenever the server endpoint is modified, instead of requiring credential re-entry or validating the destination against a fixed identifier.

Attack Vector

Exploitation requires network access to the printer's management interface and valid administrator credentials. The attacker performs the following sequence: log in to the device web interface, identify a configured integration (for example, LDAP authentication or SMTP relay), change the server hostname or IP to a system they control, and initiate a connection test. The printer transmits the stored credentials to the attacker's host, which records them. The technique is well documented for multifunction printers and does not rely on a memory corruption primitive or custom payload, which is why no public proof-of-concept code is required to abuse it.

Detection Methods for CVE-2025-3078

Indicators of Compromise

Unexpected modifications to LDAP, SMB, FTP, or SMTP server fields in the printer configuration audit log.
Outbound LDAP (TCP/389, 636), SMB (TCP/445), or SMTP (TCP/25, 587) connections from a printer to a host outside the enterprise directory or mail infrastructure.
Administrator logins to the printer web interface from non-administrative subnets or outside maintenance windows.
Authentication failures in Active Directory originating from printer service accounts shortly after configuration changes.

Detection Strategies

Baseline the destination IP addresses each printer connects to for LDAP, SMB, and SMTP, and alert on deviations.
Forward printer syslog and configuration-change events to a centralized log platform for correlation with directory authentication events.
Monitor for the printer service account authenticating from unexpected source IPs, which can indicate that harvested credentials are being reused.

Monitoring Recommendations

Place Canon MFPs on a segmented VLAN and log all egress flows at the firewall.
Enable Canon device audit logging per the Canon Hardening Guidelines and ingest logs into a SIEM.
Review administrator account activity on each device weekly and alert on changes to integration endpoints.

How to Mitigate CVE-2025-3078

Immediate Actions Required

Apply the firmware updates referenced in Canon PSIRT Advisory CP2025-004 for each affected model.
Rotate any LDAP, SMB, FTP, Kerberos, and SMTP service-account passwords currently stored on affected Canon printers.
Restrict access to the printer administration interface to a dedicated management network and remove default or shared administrator passwords.
Audit configured integration endpoints on every device and confirm they point to authorized internal servers.

Patch Information

Canon has released firmware updates for affected production printers, office and small office multifunction printers, and laser printers. Refer to Canon CP2025-004 Mitigation Guidance and the Canon Vulnerability Response Info page for the model-specific firmware versions and download links. European customers can obtain firmware through Canon Europe Product Security Support.

Workarounds

Use a dedicated, least-privilege service account for LDAP binds from printers, scoped to read-only directory queries.
Disable unused integration features (LDAP, SMB, FTP, SMTP) on printers that do not require them.
Enforce network access control lists so printers can only reach the specific LDAP, SMB, and SMTP servers they are configured to use.
Require administrators to re-enter credentials whenever an integration endpoint is modified, where the device supports that policy.

bash

# Example firewall policy restricting a printer to known integration servers
# Replace addresses with values appropriate for your environment
iptables -A FORWARD -s 10.20.30.40/32 -d 10.10.10.5/32 -p tcp --dport 389 -j ACCEPT   # LDAP
iptables -A FORWARD -s 10.20.30.40/32 -d 10.10.10.6/32 -p tcp --dport 25  -j ACCEPT   # SMTP
iptables -A FORWARD -s 10.20.30.40/32 -j DROP                                          # default deny