CVE-2018-17068 in DIR-816 A2
Summary
by MITRE
An issue was discovered on D-Link DIR-816 A2 1.10 B05 devices. An HTTP request parameter is used in command string construction in the handler function of the /goform/Diagnosis route. This could lead to command injection via shell metacharacters in the sendNum parameter.
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Analysis
by VulDB Data Team • 03/24/2020
The vulnerability identified as CVE-2018-17068 affects D-Link DIR-816 A2 1.10 B05 wireless routers, representing a critical command injection flaw that enables remote attackers to execute arbitrary system commands. This issue stems from insufficient input validation within the web interface handler for the /goform/Diagnosis route, where user-supplied parameters are directly incorporated into system command strings without proper sanitization. The specific parameter vulnerable to exploitation is sendNum, which when manipulated with shell metacharacters can trigger unauthorized command execution on the affected device. The vulnerability demonstrates a classic lack of proper input validation and output encoding, which falls under the CWE-77 principle of command injection through improper input handling. This weakness allows attackers to bypass authentication mechanisms and gain unauthorized access to the router's underlying operating system, potentially enabling full system compromise and unauthorized network access.
The technical implementation of this vulnerability occurs within the web application's backend processing logic where the sendNum parameter from HTTP requests is directly concatenated into shell command strings without proper sanitization or escaping. Attackers can exploit this by crafting malicious HTTP requests containing shell metacharacters such as semicolons, pipes, or other command delimiters within the sendNum parameter value. When the router processes these requests through the /goform/Diagnosis endpoint, the malformed input gets executed as system commands, potentially allowing attackers to execute arbitrary code with the privileges of the web server process. This type of vulnerability aligns with ATT&CK technique T1059.001 for command and scripting interpreter and represents a significant security risk given that the affected routers are commonly deployed in residential and small office environments where they may serve as entry points for broader network attacks. The vulnerability is particularly concerning because it operates at the system level, potentially allowing attackers to modify router configurations, install malware, or establish persistent backdoors.
The operational impact of CVE-2018-17068 extends beyond simple command execution, as it can enable attackers to completely compromise the affected routers and use them as launching points for further network infiltration. Once exploited, attackers can potentially gain access to the local network, monitor traffic, redirect DNS requests, or even establish reverse shells for continued access. The vulnerability affects a widely deployed device model, increasing the potential attack surface and making it particularly attractive to automated exploitation tools. Organizations and individuals using these routers face significant risks including data breaches, network monitoring, and potential use as botnet nodes for distributed denial-of-service attacks. The vulnerability's remote exploitability means that attackers do not require physical access to the device, making it a particularly dangerous flaw in the context of internet-facing network devices. Security professionals should consider this vulnerability as part of broader network security assessments, particularly when evaluating the security posture of legacy network infrastructure components that may be running unpatched firmware versions.
Mitigation strategies for CVE-2018-17068 should prioritize immediate firmware updates from D-Link to address the root cause of the vulnerability. Network administrators should implement network segmentation to isolate affected devices from critical network segments and consider disabling unnecessary web management interfaces. Access controls should be strengthened through the use of strong authentication mechanisms and regular credential rotation to minimize the impact of potential exploitation. Monitoring network traffic for suspicious patterns and implementing intrusion detection systems can help identify exploitation attempts. Additionally, organizations should conduct comprehensive vulnerability assessments of their network infrastructure to identify other potentially affected devices and ensure proper patch management processes are in place. The vulnerability underscores the importance of input validation and proper security coding practices in web application development, particularly for network device manufacturers who must consider the security implications of their code at every level of the application stack.