CVE-2017-14429 in DIR-850L
Summary
by MITRE
The DHCP client on D-Link DIR-850L REV. A (with firmware through FW114WWb07_h2ab_beta1) and REV. B (with firmware through FW208WWb02) devices allows unauthenticated remote code execution as root because /etc/services/INET/inet_ipv4.php mishandles shell metacharacters, affecting generated files such as WAN-1-udhcpc.sh.
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Analysis
by VulDB Data Team • 05/06/2025
The vulnerability CVE-2017-14429 represents a critical remote code execution flaw in D-Link DIR-850L routers across multiple firmware revisions. This vulnerability exists within the DHCP client implementation and specifically targets the handling of shell metacharacters in the inet_ipv4.php script located in the /etc/services/INET/ directory. The flaw allows attackers to execute arbitrary code with root privileges without requiring authentication, making it particularly dangerous for network infrastructure devices. The vulnerability affects both revision A and B models of the DIR-850L router, with impacted firmware versions extending through FW114WWb07_h2ab_beta1 for revision A and FW208WWb02 for revision B, highlighting the widespread nature of this security weakness across multiple firmware iterations.
The technical root cause of this vulnerability lies in improper input validation and shell command construction within the DHCP client service. The inet_ipv4.php script fails to properly sanitize user-supplied data from DHCP responses before incorporating it into shell commands. When the DHCP client processes network configuration parameters, it passes these values directly to shell commands without adequate escaping or validation, creating a classic shell injection vulnerability. This vulnerability maps to CWE-77 which specifically addresses "Improper Neutralization of Special Elements used in a Command ('Command Injection')". The compromised file WAN-1-udhcpc.sh serves as the execution vector where maliciously crafted DHCP responses can inject shell commands that execute with root privileges due to the router's privileged execution context.
The operational impact of this vulnerability extends far beyond simple remote code execution, as it provides attackers with complete system control over affected routers. An attacker can leverage this vulnerability to establish persistent backdoors, modify network configurations, redirect traffic, or even use the compromised device as a pivot point for attacking other systems within the local network. The lack of authentication requirements means that any remote attacker can exploit this vulnerability, making it particularly attractive for automated attacks. This vulnerability directly aligns with ATT&CK technique T1059.007 for "Command and Scripting Interpreter: Unix Shell" and represents a critical compromise of network infrastructure devices that can affect entire network segments. The vulnerability's impact is amplified by the fact that routers often serve as central network points, making them ideal targets for network infiltration and lateral movement attacks.
Mitigation strategies for CVE-2017-14429 should focus on immediate firmware updates from D-Link, as the vendor has released patches addressing this specific vulnerability. Organizations should also implement network segmentation and access controls to limit the potential impact of exploitation. Additional protective measures include monitoring for unusual DHCP activity, implementing network intrusion detection systems to identify malicious DHCP responses, and disabling unnecessary DHCP client functionality when not required. The vulnerability demonstrates the importance of proper input validation and shell command construction in embedded systems, emphasizing the need for secure coding practices and regular security assessments of network infrastructure devices. Security teams should also consider implementing network monitoring solutions that can detect anomalous behavior patterns consistent with exploitation attempts, particularly focusing on DHCP-related traffic and shell command execution patterns within the network infrastructure.