CVE-2017-20221: Telesquare LTE Router CSRF Vulnerability

CVE-2017-20221 Overview

CVE-2017-20221 is a Cross-Site Request Forgery (CSRF) vulnerability affecting the Telesquare SKT LTE Router SDT-CS3B1 version 1.2.0. This vulnerability allows authenticated attackers to execute arbitrary system commands by exploiting missing request validation in the router's administrative interface. Attackers can craft malicious web pages that perform administrative actions when visited by logged-in users, enabling command execution with router privileges.

Critical Impact

Successful exploitation allows attackers to execute arbitrary system commands on the router with administrative privileges, potentially leading to complete device compromise, network infiltration, and persistent backdoor access.

Affected Products

• Telesquare SKT LTE Router SDT-CS3B1 version 1.2.0

Discovery Timeline

• 2026-03-16 - CVE CVE-2017-20221 published to NVD
• 2026-03-16 - Last updated in NVD database

Technical Details for CVE-2017-20221

Vulnerability Analysis

This vulnerability is classified as CWE-352 (Cross-Site Request Forgery). The Telesquare SKT LTE Router SDT-CS3B1 fails to implement proper CSRF protections on its administrative interfaces. When an authenticated administrator visits a malicious webpage crafted by an attacker, the browser automatically includes session cookies with any requests made to the router. Because the router does not validate the origin of these requests or require anti-CSRF tokens, it processes the malicious requests as legitimate administrative commands.

The vulnerability is particularly concerning because it can be chained with system command execution functionality, allowing attackers to run arbitrary commands on the underlying operating system with the privileges of the router's web service.

Root Cause

The root cause of CVE-2017-20221 is the absence of CSRF protection mechanisms in the router's web administration interface. The router does not implement anti-CSRF tokens, origin header validation, or other standard defenses against forged cross-site requests. Additionally, the administrative interface allows system command execution through HTTP requests without additional authentication challenges or confirmation steps.

Attack Vector

The attack vector is network-based, requiring the victim (an authenticated administrator) to visit a malicious webpage while logged into the router's administrative interface. The attacker hosts a crafted HTML page containing hidden forms or JavaScript that automatically submits requests to the router. When the victim's browser loads this page, it sends the malicious requests along with the victim's valid session cookies, causing the router to execute the attacker's commands.

The exploitation flow involves:

1. Attacker identifies a victim who has administrative access to the vulnerable router
2. Attacker crafts a malicious webpage containing hidden requests to the router's command execution endpoints
3. Attacker delivers the malicious page to the victim via phishing, compromised website, or malvertising
4. Victim visits the malicious page while authenticated to the router
5. Browser sends forged requests to the router with valid session credentials
6. Router executes attacker-specified system commands

Technical details and proof-of-concept information are available through the Exploit-DB #43400 advisory and the Zero Science ZSL-2017-5443 Vulnerability disclosure.

Detection Methods for CVE-2017-20221

Indicators of Compromise

• Unexpected system configuration changes on the router without administrator action
• Presence of unauthorized user accounts or modified credentials
• Suspicious outbound network connections from the router to unknown IP addresses
• Modified DNS settings or routing tables indicating traffic redirection

Detection Strategies

• Monitor web server logs on the router for administrative requests originating from unexpected referrer headers
• Implement network monitoring to detect anomalous command execution patterns on the router
• Review browser history and network logs for connections to suspicious external sites coinciding with router configuration changes
• Deploy network intrusion detection signatures for known CSRF exploitation patterns targeting embedded devices

Monitoring Recommendations

• Enable verbose logging on the router's administrative interface if available
• Monitor for POST requests to system command execution endpoints with external referrer values
• Implement network segmentation to isolate router management interfaces from general user traffic
• Consider deploying a web application firewall or proxy that can detect and block CSRF attacks targeting internal network devices

How to Mitigate CVE-2017-20221

Immediate Actions Required

• Restrict access to the router's administrative interface to trusted IP addresses only
• Use a separate browser profile or session exclusively for router administration
• Avoid browsing external websites while logged into the router's administrative interface
• Implement network segmentation to isolate management interfaces from user networks

Patch Information

No vendor patch information is available in the CVE data. Organizations should contact Telesquare directly to inquire about firmware updates that address this vulnerability. Additional technical details and advisories can be found at CXSecurity Issue WLB-2017120299 and IBM X-Force Vulnerability #136839.

Workarounds

• Configure firewall rules to restrict access to the router's management interface to specific trusted IP addresses
• Log out of the router's administrative interface immediately after completing administrative tasks
• Consider placing the router's management interface on an isolated VLAN accessible only from a dedicated management workstation
• If possible, disable remote administration and require physical or console access for configuration changes

# Example: Restrict management access to specific IP using iptables on an upstream firewall
iptables -A INPUT -p tcp --dport 80 -s 192.168.1.100 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -s 192.168.1.100 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP
iptables -A INPUT -p tcp --dport 443 -j DROP