CVE-2017-11436 in DIR-615
Summary
by MITRE
D-Link DIR-615 before v20.12PTb04 has a second admin account with a 0x1 BACKDOOR value, which might allow remote attackers to obtain access via a TELNET connection.
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Analysis
by VulDB Data Team • 10/27/2019
The CVE-2017-11436 vulnerability affects D-Link DIR-615 wireless routers running firmware versions prior to v20.12PTb04, presenting a critical backdoor access mechanism that compromises network security. This vulnerability manifests through a hardcoded administrative account that operates with a specific 0x1 BACKDOOR value, creating an unauthorized entry point for remote attackers. The flaw is particularly concerning because it allows adversaries to establish TELNET connections to the device without proper authentication, effectively bypassing all standard security controls. The presence of such a backdoor in network infrastructure devices represents a fundamental breach of security principles and exposes organizations to potential unauthorized access and data compromise.
The technical implementation of this vulnerability involves a hardcoded credential mechanism embedded within the router firmware that operates at the system level. When the router processes incoming TELNET connections, it checks for the specific 0x1 BACKDOOR value as a valid authentication token, allowing any remote attacker who knows this value to gain administrative privileges. This backdoor operates at the network layer and can be exploited without requiring any prior knowledge of legitimate user credentials or passwords. The vulnerability is classified under CWE-259 as a "Use of Hard-coded Password" and represents a significant weakness in the device's authentication architecture. The 0x1 BACKDOOR value essentially acts as a magic number that triggers the bypass mechanism, making it easily recognizable to attackers who may have discovered this pattern through reverse engineering or public research.
The operational impact of CVE-2017-11436 extends far beyond simple unauthorized access, as it provides attackers with complete administrative control over the affected router. Once an attacker gains access through this backdoor, they can modify network configurations, redirect traffic, implement man-in-the-middle attacks, and potentially use the compromised device as a pivot point for accessing other systems within the network. The TELNET protocol used for this backdoor access is inherently insecure and transmits credentials in plaintext, making it susceptible to network sniffing attacks. This vulnerability aligns with ATT&CK technique T1078.004 for Valid Accounts and T1021.001 for Remote Services, as it enables adversaries to establish persistent access through legitimate network services. Organizations running affected D-Link DIR-615 devices face potential data breaches, network disruption, and compliance violations that could result in significant financial and reputational damage.
Mitigation strategies for CVE-2017-11436 require immediate firmware updates to the latest available version that addresses this backdoor vulnerability. Network administrators should implement network segmentation and access controls to limit the potential impact of compromised devices, while also monitoring network traffic for suspicious TELNET connections. The vulnerability demonstrates the critical importance of supply chain security and the need for regular firmware updates, as highlighted in NIST SP 800-128 guidelines for managing software vulnerabilities. Organizations should conduct comprehensive network assessments to identify all affected devices and implement network monitoring solutions that can detect unauthorized TELNET connections. Additionally, the vulnerability underscores the necessity of following secure coding practices and conducting thorough security reviews of embedded systems to prevent the inclusion of hardcoded credentials or backdoor mechanisms in network infrastructure devices, as recommended by the OWASP Top Ten security framework.