CVE-2019-16920 in DIR-655C
Summary
by MITRE
Unauthenticated remote code execution occurs in D-Link products such as DIR-655C, DIR-866L, DIR-652, and DHP-1565. The issue occurs when the attacker sends an arbitrary input to a "PingTest" device common gateway interface that could lead to common injection. An attacker who successfully triggers the command injection could achieve full system compromise. Later, it was independently found that these are also affected: DIR-855L, DAP-1533, DIR-862L, DIR-615, DIR-835, and DIR-825.
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Analysis
by VulDB Data Team • 11/07/2025
The vulnerability identified as CVE-2019-16920 represents a critical command injection flaw affecting multiple D-Link networking devices including DIR-655C, DIR-866L, DIR-652, and DHP-1565 models. This security weakness stems from insufficient input validation within the device's Common Gateway Interface implementation, specifically within the PingTest functionality that allows remote attackers to execute arbitrary commands without authentication. The flaw manifests when malicious input is passed through the PingTest interface, enabling attackers to inject and execute system commands directly on the affected devices. This vulnerability is particularly dangerous because it operates entirely without requiring authentication credentials, making it accessible to any remote attacker who can reach the device's network interface. The affected devices are commonly deployed in residential and small office environments, where they serve as primary network gateways and routers, making them attractive targets for attackers seeking persistent access to network infrastructure. The vulnerability has been classified under CWE-77 and CWE-94, representing command injection and code injection weaknesses respectively, which aligns with the ATT&CK framework's T1059.001 technique for command and scripting interpreter. The impact extends beyond simple command execution to full system compromise, as successful exploitation allows attackers to gain complete control over the device's operating system, potentially enabling them to modify network configurations, install malicious software, or establish backdoors for continued access. The vulnerability affects not only the initially reported devices but also several additional models including DIR-855L, DAP-1533, DIR-862L, DIR-615, DIR-835, and DIR-825, indicating a widespread issue within D-Link's product line that requires immediate attention. The attack vector is particularly concerning as it requires no prior authentication and can be exploited remotely, making it suitable for automated attacks and large-scale exploitation campaigns. Network administrators should be aware that these devices may be silently compromised without any visible signs of intrusion, as the command injection can occur through normal network traffic. The vulnerability's exploitation potential aligns with ATT&CK's T1068 technique for exploit for privilege escalation, where attackers can leverage the command injection to gain elevated privileges and full system control. The affected devices typically run embedded operating systems that may lack proper input sanitization mechanisms, allowing attackers to pass malicious payloads through the PingTest interface. Security researchers have documented that the vulnerability can be exploited to perform actions such as modifying firewall rules, changing network settings, or even installing persistent malware on the devices. The lack of authentication requirements makes this vulnerability particularly dangerous in environments where devices are accessible from untrusted networks or the internet, as attackers can immediately exploit the flaw without needing to bypass initial authentication mechanisms. Organizations should consider implementing network segmentation and access controls to limit exposure to these vulnerable devices, while also monitoring for unusual network traffic patterns that might indicate exploitation attempts. The vulnerability demonstrates the importance of proper input validation in embedded systems and highlights the risks associated with providing remote management capabilities without adequate authentication mechanisms. Given the widespread nature of affected D-Link products, the vulnerability represents a significant risk to network security and requires immediate remediation through firmware updates provided by D-Link. The exploitation of this vulnerability can lead to complete network compromise, as attackers can use the compromised devices as stepping stones to target other systems within the network infrastructure. The technical flaw essentially allows attackers to bypass normal device security controls and execute arbitrary code with the privileges of the device's operating system, making it a critical security concern for all organizations using affected D-Link devices.