CVE-2017-20223

Executive Summary

CVE-2017-20223 is an Insecure Direct Object Reference (IDOR) vulnerability in the Telesquare SKT LTE Router SDT-CS3B1 firmware version 1.2.0. This flaw allows unauthenticated or low-privileged attackers to bypass authorization checks by manipulating user-supplied input parameters (e.g., object IDs, file paths, or API parameters). Successful exploitation enables attackers to access sensitive information (configuration files, user credentials, network logs) and invoke privileged functions without proper access controls. The vulnerability is publicly known but remains unpatched, posing a persistent risk to deployed devices.

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 device.

CVSS Breakdown & Threat Level

CVSS Score: 0.0 (No official vector assigned) Threat Level: High (based on impact and ease of exploitation)

Rationale: While no CVSS vector is officially published, the vulnerability allows unauthorized access to sensitive data and functionality. Attackers can exploit this remotely if the device is exposed to the internet or internal network. The lack of a patch increases the risk.

Deep Dive & Mechanics

The vulnerability resides in the web management interface of the Telesquare SKT LTE Router SDT-CS3B1. The application fails to validate whether a user is authorized to access a specific object (e.g., a configuration file, a user account, or a system command). By simply changing a parameter in a URL or POST request (e.g., id=123 to id=456), an attacker can access resources belonging to other users or administrative functions.

Example Attack Vector:

• Normal request: GET /api/getConfig?id=1 (returns own config)
• Malicious request: GET /api/getConfig?id=2 (returns another user's config)

The application does not check if the requesting user owns or is permitted to access object ID 2.

Vulnerable vs. Patched Code

Vulnerable Code (Firmware 1.2.0):

# Pseudocode for vulnerable endpoint
@app.route('/api/getConfig')
def get_config():
    config_id = request.args.get('id')
    # No authorization check
    config = db.query("SELECT * FROM configs WHERE id = ?", config_id)
    return jsonify(config)

Patched Code (Hypothetical):

# Pseudocode for patched endpoint
@app.route('/api/getConfig')
def get_config():
    config_id = request.args.get('id')
    user_id = get_current_user_id()
    # Authorization check: ensure user owns the config
    config = db.query("SELECT * FROM configs WHERE id = ? AND user_id = ?", config_id, user_id)
    if config is None:
        return "Unauthorized", 403
    return jsonify(config)

Exploitation & Lab Setup

Red Team (Attack Simulation)

Lab Environment:

• Telesquare SKT LTE Router SDT-CS3B1 (firmware 1.2.0)
• Attacker machine (Kali Linux)
• Network connectivity to the router's management interface (default IP: 192.168.1.1)

Exploitation Steps:

1. Identify the management interface (e.g., http://192.168.1.1).
2. Enumerate endpoints using a tool like Burp Suite or ffuf.
3. Discover an IDOR-prone endpoint (e.g., /api/getConfig?id=1).
4. Manipulate the id parameter to access other objects:

   curl "http://192.168.1.1/api/getConfig?id=2"
   curl "http://192.168.1.1/api/getConfig?id=3"
   

5. Extract sensitive data (e.g., admin credentials, network keys).

No Exploit-DB code provided.

Blue Team (Defense & Detection)

Detection Steps:

1. Monitor for unusual parameter manipulation in HTTP requests (e.g., sequential IDs, large numbers).
2. Implement logging of all API access attempts.
3. Use a Web Application Firewall (WAF) to block requests with suspicious patterns.
4. Conduct regular vulnerability scans.

Indicators of Compromise (IOCs)

• Network IOCs:
  • HTTP requests with sequential or out-of-range id parameters.
  • Access to /api/getConfig, /api/getUser, or similar endpoints from unknown IPs.
• File IOCs:
  • Unauthorized access to /etc/shadow or /var/log/syslog via web interface.
• Behavioral IOCs:
  • Multiple failed login attempts followed by successful access to admin functions.

Detection Engineering

YARA Rule

rule CVE_2017_20223_IDOR_Detection {
    meta:
        description = "Detects IDOR exploitation attempts on Telesquare SKT LTE Router"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2017-20223"
    strings:
        $s1 = "/api/getConfig" ascii wide nocase
        $s2 = "/api/getUser" ascii wide nocase
        $s3 = "id=" ascii wide nocase
    condition:
        any of ($s*) and #s3 > 5
}

Sigma Rule

title: IDOR Exploitation Attempt on Telesquare Router
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects potential IDOR attacks against Telesquare SKT LTE Router
author: Valters IT
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'GET'
        cs-uri-query|contains: '/api/getConfig?id='
    condition: selection
falsepositives:
    - Legitimate admin access
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2017-20223 IDOR Attempt"; flow:to_server,established; content:"/api/getConfig"; http_uri; content:"id="; http_uri; pcre:"/id=\d{2,}/"; classtype:attempted-recon; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Isolate affected devices: Place the router behind a firewall and restrict management access to trusted IPs only.
2. Disable remote management: If not required, disable the web interface from the WAN side.
3. Apply vendor patch: Contact Telesquare for a firmware update. If unavailable, consider replacing the device.

Long-term Fixes:

• Implement proper authorization checks on all API endpoints.
• Use session-based authentication with role-based access control (RBAC).
• Conduct regular security audits and penetration testing.

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