CVE-2019-20215 in DIR-859
Summary
by MITRE
D-Link DIR-859 1.05 and 1.06B01 Beta01 devices allow remote attackers to execute arbitrary OS commands via a urn: to the M-SEARCH method in ssdpcgi() in /htdocs/cgibin, because HTTP_ST is mishandled. The value of the urn: service/device is checked with the strstr function, which allows an attacker to concatenate arbitrary commands separated by shell metacharacters.
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Analysis
by VulDB Data Team • 01/02/2025
The vulnerability CVE-2019-20215 affects D-Link DIR-859 routers running firmware versions 1.05 and 1.06B01 Beta01, presenting a critical remote command execution flaw that enables attackers to gain unauthorized control over affected devices. This vulnerability resides within the ssdpcgi() function in the /htdocs/cgibin directory of the affected router firmware, specifically targeting the M-SEARCH method implementation. The flaw stems from improper handling of the HTTP_ST parameter during the processing of Simple Service Discovery Protocol (SSDP) requests, creating a pathway for malicious actors to inject and execute arbitrary operating system commands on the device.
The technical exploitation of this vulnerability relies on the insecure use of the strstr function to validate the urn: service/device parameter in the M-SEARCH method. This validation mechanism fails to properly sanitize input, allowing attackers to append malicious commands using shell metacharacters such as semicolons, ampersands, or pipes. When the device processes these malformed requests, the system interprets the concatenated commands as legitimate instructions, executing them with the privileges of the web server process. This represents a classic command injection vulnerability that falls under CWE-77, which specifically addresses improper neutralization of special elements used in commands.
The operational impact of this vulnerability extends beyond simple unauthorized access, as it provides attackers with complete control over the affected router's functionality. An attacker could potentially modify network configurations, redirect traffic, establish backdoors, or use the device as a pivot point for further attacks within the network. The remote nature of the exploitation means that attackers do not require physical access to the device, making this vulnerability particularly dangerous in both home and enterprise environments where such devices are commonly deployed. This aligns with ATT&CK technique T1059.001 for command and scripting interpreter, specifically focusing on the execution of system commands through legitimate interfaces.
The vulnerability demonstrates a fundamental flaw in input validation and sanitization practices within the router's web interface implementation. The failure to properly validate and escape user-supplied input before incorporating it into system commands creates an attack surface that can be leveraged for privilege escalation and persistent access. Network administrators should consider implementing network segmentation and monitoring to detect anomalous traffic patterns that might indicate exploitation attempts, while also ensuring that affected devices are promptly updated with patched firmware releases from D-Link. The vulnerability highlights the importance of secure coding practices and input validation in embedded systems, particularly those handling network protocols and user interactions through web interfaces.