CVE-2016-5791 in JTC-200
Summary
by MITRE
An Improper Authentication issue was discovered in JanTek JTC-200, all versions. The improper authentication could provide an undocumented BusyBox Linux shell accessible over the TELNET service without any authentication.
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Analysis
by VulDB Data Team • 11/24/2019
The vulnerability identified as CVE-2016-5791 represents a critical authentication flaw in JanTek JTC-200 network devices across all software versions. This issue stems from a fundamental misconfiguration in the device's security architecture that allows unauthorized access to a hidden command shell through the TELNET service. The vulnerability exposes a backdoor mechanism that bypasses normal authentication procedures, creating a significant security risk for organizations deploying these devices in production environments.
The technical implementation of this flaw involves the device's TELNET daemon failing to properly validate user credentials before granting shell access. This improper authentication mechanism creates an undocumented entry point that operates outside the normal security controls. The vulnerability specifically affects the BusyBox Linux shell implementation within the device's firmware, which remains accessible without any form of authentication or authorization checks. This type of flaw typically falls under CWE-287, which addresses improper authentication issues in software systems.
From an operational perspective, this vulnerability presents a severe threat to network security infrastructure. Attackers can exploit this weakness to gain root-level access to the device without requiring legitimate credentials, potentially enabling them to modify device configurations, install malicious software, or use the device as a pivot point for attacking other systems within the network. The TELNET service, being a standard protocol for remote device management, becomes a vector for unauthorized access when proper authentication is not enforced. This vulnerability directly aligns with ATT&CK technique T1021.001, which covers remote services such as telnet, and T1059.004, which involves command and scripting interpreters.
The impact extends beyond immediate device compromise to include potential lateral movement within network environments. Once an attacker gains access through this backdoor, they can leverage the device's network connectivity to probe internal systems, potentially accessing sensitive data or critical infrastructure components. Organizations using JanTek JTC-200 devices face the risk of complete network infiltration, as the compromised device can serve as a persistent access point for attackers. The vulnerability's persistence across all versions indicates a fundamental flaw in the device's design rather than a simple software bug that could be patched.
Mitigation strategies for this vulnerability require immediate action to address the unauthorized access point. Organizations should disable the TELNET service on affected devices when possible, or implement strict network segmentation to isolate these devices from critical network segments. Network administrators should also conduct thorough vulnerability assessments to identify any other devices that might be running vulnerable firmware versions. The implementation of network access controls, including firewall rules that restrict TELNET access to authorized management systems, provides an additional layer of protection. Regular firmware updates and security audits become essential practices to prevent similar issues in the future, as this vulnerability demonstrates the importance of proper authentication mechanisms in embedded network devices.