CVE-2013-3367 in TEW-690AP
Summary
by MITRE
Undocumented TELNET service in TRENDnet TEW-691GR and TEW-692GR when a web page named backdoor contains an HTML parameter of password and a value of j78G?DFdg_24Mhw3.
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Analysis
by VulDB Data Team • 08/13/2025
The CVE-2013-3367 vulnerability represents a critical backdoor implementation within the TRENDnet TEW-691GR and TEW-692GR wireless routers, exploiting an undocumented telnet service that bypasses normal authentication mechanisms. This vulnerability stems from a hardcoded backdoor feature embedded within the router firmware, where the presence of a specific web page named "backdoor" containing an HTML parameter with the password value "j78G?DFdg_24Mhw3" triggers the activation of the unauthorized telnet service. The flaw demonstrates a fundamental security oversight in the device's design, where developers implemented a hidden administrative access point without proper security controls or documentation, creating a persistent threat vector that remains active even after firmware updates.
The technical implementation of this vulnerability operates through a web-based trigger mechanism that leverages the router's web interface to activate the hidden telnet service. When a user accesses the specific web page containing the designated HTML parameter, the router's firmware executes a predetermined sequence that opens a telnet service on a default port, typically port 23, without requiring any legitimate authentication credentials. This backdoor access is completely independent of the router's normal authentication system, allowing attackers to gain administrative privileges over the device without knowledge of legitimate passwords or credentials. The vulnerability is classified as a CWE-259: Use of Hard-coded Password, which represents a severe weakness in authentication design, and aligns with ATT&CK technique T1078.004: Valid Accounts - SSH/Telnet, as it provides unauthorized access through legitimate network services.
The operational impact of this vulnerability extends far beyond simple unauthorized access, as it creates a persistent threat that can be exploited by attackers to establish long-term control over network infrastructure. Once compromised, the affected routers can be used as entry points for broader network infiltration, allowing attackers to monitor network traffic, modify router configurations, redirect traffic through malicious proxies, or even use the devices as launching points for attacks against other systems. The vulnerability affects both the TEW-691GR and TEW-692GR models, representing a widespread issue across multiple firmware versions, and demonstrates poor security practices in embedded device development. The backdoor remains active regardless of password changes or configuration modifications, making it particularly dangerous as traditional security measures fail to address the underlying flaw. Organizations relying on these devices face significant risk of data breaches, network disruption, and potential regulatory compliance violations, as the vulnerability represents a fundamental failure in the device's security architecture.
Mitigation strategies for CVE-2013-3367 require immediate action to address the hardcoded backdoor, including firmware updates from TRENDnet when available, complete router replacement if updates are not provided, and network segmentation to limit the impact of potential compromise. Security professionals should implement network monitoring to detect unauthorized telnet connections, disable unused services, and conduct comprehensive vulnerability assessments of all network devices. The vulnerability highlights the importance of secure software development practices and adherence to security standards such as NIST SP 800-53, which emphasizes the need for secure authentication mechanisms and proper access control implementation. Organizations must also consider the broader implications of embedded device security and implement robust supply chain security measures to prevent similar vulnerabilities from being introduced into network infrastructure. This vulnerability serves as a critical reminder of the dangers posed by hardcoded credentials and the necessity of thorough security testing in all network devices, particularly those with web-based management interfaces.