CVE-2017-20223: Telesquare LTE Router Auth Bypass Flaw

CVE-2017-20223 Overview

CVE-2017-20223 is an Insecure Direct Object Reference (IDOR) vulnerability affecting the Telesquare SKT LTE Router SDT-CS3B1 running firmware version 1.2.0. This vulnerability allows unauthenticated remote attackers to bypass authorization mechanisms and directly access system resources by manipulating user-supplied input parameters. Exploitation enables attackers to retrieve sensitive information and access restricted functionalities without proper access controls.

Critical Impact

Unauthenticated remote attackers can bypass authorization controls to access sensitive router configurations, credentials, and administrative functions through parameter manipulation.

Affected Products

• Telesquare SKT LTE Router SDT-CS3B1 firmware version 1.2.0

Discovery Timeline

• 2026-03-16 - CVE CVE-2017-20223 published to NVD
• 2026-03-16 - Last updated in NVD database

Technical Details for CVE-2017-20223

Vulnerability Analysis

The Telesquare SKT LTE Router SDT-CS3B1 contains an Insecure Direct Object Reference (IDOR) vulnerability classified under CWE-639 (Authorization Bypass Through User-Controlled Key). The router's web interface fails to properly validate whether a user is authorized to access the specific resource they are requesting. Instead of implementing proper authorization checks, the application directly uses user-supplied input to reference internal objects such as configuration files, user accounts, or system resources.

This architectural flaw allows attackers to manipulate parameters in HTTP requests to access objects belonging to other users or administrative functions without authentication. The vulnerability is particularly severe in network infrastructure devices like LTE routers, as successful exploitation can lead to complete device compromise, credential theft, and potential network-wide attacks.

Root Cause

The root cause of this vulnerability lies in the router's failure to implement proper authorization verification when processing user requests. The firmware directly references internal objects based on user-controlled input parameters without validating whether the requesting user has permission to access those resources. This represents a fundamental broken access control design flaw where the application trusts client-supplied identifiers without server-side authorization enforcement.

Attack Vector

The vulnerability is exploitable remotely over the network without requiring any authentication or user interaction. An attacker can craft malicious HTTP requests to the router's web management interface, manipulating object reference parameters such as user IDs, file paths, or configuration identifiers. By systematically enumerating these parameters, attackers can discover and access sensitive resources including configuration backups, stored credentials, and administrative interfaces. The attack requires no special privileges and can be performed by any network-adjacent or internet-facing attacker who can reach the router's management interface.

Technical details and proof-of-concept information are available through the Zero Science Lab advisory (ZSL-2017-5445) and Exploit-DB #43402.

Detection Methods for CVE-2017-20223

Indicators of Compromise

• Unusual HTTP requests to the router's web interface containing manipulated object reference parameters
• Access logs showing sequential or enumerated parameter values indicating brute-force object enumeration
• Unauthorized access to configuration files or sensitive resources from unexpected source IP addresses
• Authentication bypass attempts targeting administrative endpoints without valid session tokens

Detection Strategies

• Monitor web server access logs for requests with sequential or predictable parameter patterns that may indicate IDOR exploitation attempts
• Implement network intrusion detection rules to identify HTTP requests targeting known vulnerable endpoints on Telesquare routers
• Deploy network monitoring to detect anomalous traffic patterns to router management interfaces from untrusted sources
• Review authentication logs for access patterns that bypass normal login workflows

Monitoring Recommendations

• Restrict management interface access to trusted IP addresses and monitor for connections from unauthorized sources
• Enable verbose logging on the router's web interface to capture all access attempts and parameter values
• Implement network segmentation to isolate router management interfaces from general network traffic
• Monitor for firmware version changes or configuration modifications that could indicate post-exploitation activity

How to Mitigate CVE-2017-20223

Immediate Actions Required

• Restrict access to the router's web management interface to trusted IP addresses only using firewall rules
• Disable remote management access if not required for operations
• Segment the management network to prevent unauthorized access from untrusted network zones
• Audit current router configurations for any unauthorized changes or suspicious settings

Patch Information

No official vendor patch information is available in the CVE data. Organizations should contact Telesquare directly for firmware updates or consider replacing vulnerable devices with supported alternatives. Additional technical details can be found in the VulnCheck Advisory and IBM X-Force Vulnerability #136993.

Workarounds

• Implement network-level access controls using firewall rules to restrict management interface access to specific administrator IP addresses
• Deploy a VPN or jump host requirement for accessing router management interfaces
• Place the router's management interface on an isolated management VLAN inaccessible from general user networks
• Consider deploying a web application firewall (WAF) to filter malicious requests targeting the vulnerable interface

# Example firewall rule to restrict management access (iptables)
# Allow management access only from trusted admin subnet
iptables -A INPUT -p tcp --dport 80 -s 10.0.0.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -s 10.0.0.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP
iptables -A INPUT -p tcp --dport 443 -j DROP