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Sdt Cs3b1 CVE-2017-20223

| EUVDEUVD-2017-18939 CRITICAL
Authorization Bypass Through User-Controlled Key (CWE-639)
2026-03-16 VulnCheck
9.3
CVSS 4.0 · NVD
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Vulnerability Assessment

Weakness
CWE
OWASP Top 10:2025
A01:2025 - Broken Access Control
ASVS 5.0
V8 - Authorization Object-level authorization, IDOR prevention
Impact

This vulnerability presents a critical real-world risk. The CVSS 3.1 vector (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H) indicates it's remotely exploitable over the network with low attack complexity, requires no privileges or user interaction, and impacts confidentiality, integrity, and availability at the highest level. The existence of multiple public exploits (Exploit-DB, PacketStorm Security) significantly increases the risk. While no EPSS score or KEV listing is mentioned, the combination of a weaponized exploit, network accessibility, and complete system compromise capability makes this a priority vulnerability for any organization using affected routers.

Exploit ScenarioDerived

An attacker can remotely exploit this vulnerability without any credentials or user interaction. By manipulating URL parameters or form inputs sent to the router's web interface, the attacker can directly reference and access sensitive objects such as configuration files, user credentials, or administrative functions. Given the public availability of working exploits on Exploit-DB (#43402) and PacketStorm Security, even low-skilled attackers can compromise these routers to gain full control, potentially accessing the internal network, intercepting traffic, or using the device as a pivot point for further attacks.

Act Now Prioritize within 24-48h. Why: CRITICAL severity + public POC available.
No patch listed yet 0.1% exploitation probability (EPSS)

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AnalysisAIv1 – Mar 16, 2026

An insecure direct object reference vulnerability in Telesquare SKT LTE Router SDT-CS3B1 firmware version 1.2.0 allows remote attackers to bypass authentication and directly access sensitive resources by manipulating input parameters. With a publicly available proof-of-concept exploit and a critical CVSS score of 9.8, attackers can gain unauthorized access to sensitive information and system functionalities without any authentication or user interaction required.

RemediationAI

No specific patch information is provided in the available references. Organizations should immediately contact Telesquare for an updated firmware version beyond 1.2.0. As an interim mitigation, affected routers should be placed behind additional security controls, access should be restricted to trusted IP addresses only, and network segmentation should be implemented to limit potential impact. Monitor router logs for suspicious access attempts and consider replacing the device if no patch is available.

Affected VersionsENISA

SDT-CS3B1 1.2.0

Affected Packages

euvd sdt_cs3b1 no fix

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 1 package in euvd

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

The vulnerability affects the Telesquare SDT-CS3B1 LTE router, specifically firmware version 1.2.0 (CPE: cpe:2.3:a:telesquare:sdt-cs3b1:*:*:*:*:*:*:*:*). This is an insecure direct object reference (IDOR) vulnerability classified as CWE-639, which occurs when an application exposes direct references to internal objects like database keys or filenames in URLs or form parameters. Attackers can manipulate these references to access unauthorized data or functionality, effectively bypassing the router's authentication mechanisms.

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Severity by source

NVD PRIMARY 9.3 CRITICAL
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

Attack Vector
Network
Attack Complexity
Low
Attack Requirements
None
Privileges Required
None
User Interaction
None
Vulnerable system: Confidentiality
High
Vulnerable system: Integrity
High
Vulnerable system: Availability
High
Subsequent system: Confidentiality
None
Subsequent system: Integrity
None
Subsequent system: Availability
None

Lifecycle Timeline

3
CVSS changed
Apr 14, 2026 - 17:07 NVD
9.8 (CRITICAL) 9.3 (CRITICAL)
PoC Detected
Mar 16, 2026 - 14:53 vuln.today
Public exploit code
CVE Published
Mar 16, 2026 - 01:28 nvd
CRITICAL 9.8

DescriptionCVE.org

Telesquare SKT LTE Router SDT-CS3B1 firmware version 1.2.0 contains an insecure direct object reference vulnerability that allows attackers to bypass authorization and access resources by manipulating user-supplied input parameters. Attackers can directly reference objects in the system to retrieve sensitive information and access functionalities without proper access controls.

Executive ViewAI

Why It Matters

A critical authentication bypass vulnerability (CVE-2017-20223) in Telesquare SKT LTE Router SDT-CS3B1 firmware allows remote attackers to access sensitive system resources without credentials. With a publicly available exploit and no patch available, any organization using this router model faces immediate risk of unauthorized access to network infrastructure, configuration data, and potentially lateral movement into connected systems.

Business Impact: Severe
Compensating Controls

Implement network segmentation to restrict direct access to affected routers; disable all remote management interfaces (SSH, HTTP, HTTPS); place routers behind an authenticated WAF or proxy with strict access controls; restrict router management to dedicated administrative VLANs only; implement intrusion detection rules to monitor for CVE-2017-20223 exploitation attempts; consider complete hardware replacement as this device is unsupported and no patch will be available.

Threat Intelligence Overview

EPSS Score
0.1%
Top 84% exploitable
Exploit
POC
Public exploit code exists
Data Quality
5 sources
Confidence: Medium

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity CRITICAL
CISA KEV No
Public POC Yes
EPSS 0.1%
Patch available No
Active threat No
Deciding rule
CRITICAL severity + public POC available
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived
Out-of-Cycle
Exploitation· derived
Poc
System Exposure· derived
Open
Automatable· derived
Yes
Human Impact
Very High

Priority Score

66
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +46
PoC: +20
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Authentication bypass attacks exploit flaws in the verification mechanisms that control access to systems and applications.

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