CVE-2019-17508 in DIR-850
Summary
by MITRE
On D-Link DIR-859 A3-1.06 and DIR-850 A1.13 devices, /etc/services/DEVICE.TIME.php allows command injection via the $SERVER variable.
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Analysis
by VulDB Data Team • 01/08/2024
The vulnerability identified as CVE-2019-17508 affects D-Link DIR-859 A3-1.06 and DIR-850 A1.13 wireless routers, representing a critical command injection flaw within the device's web interface scripting components. This vulnerability resides in the /etc/services/DEVICE.TIME.php file where the $SERVER variable is improperly handled, creating an avenue for malicious actors to execute arbitrary commands on the affected devices. The flaw demonstrates characteristics consistent with CWE-77 command injection, where user-supplied input is directly incorporated into system commands without adequate sanitization or validation. The affected devices operate on embedded web servers that process HTTP requests and generate responses through server-side scripts, making the web interface a prime target for exploitation. Attackers can leverage this vulnerability by crafting malicious requests that manipulate the $SERVER variable, potentially gaining unauthorized access to the router's underlying operating system and executing commands with the privileges of the web server process.
The operational impact of this vulnerability extends beyond simple unauthorized access, as it enables full system compromise of the affected routers. An attacker who successfully exploits this command injection vulnerability can execute arbitrary code on the device, potentially leading to complete network takeover, data exfiltration, or the establishment of persistent backdoors. The vulnerability affects devices running specific firmware versions where the $SERVER variable is used in command construction without proper input validation or sanitization. This flaw particularly impacts enterprise and home networks that rely on these routers for internet connectivity, as compromised devices can serve as launching points for broader network attacks or be used to conduct man-in-the-middle operations against connected devices. The vulnerability's exploitation requires minimal privileges since the web interface typically operates with elevated permissions necessary for router management functions.
Security professionals should implement immediate mitigation strategies including firmware updates from D-Link, network segmentation to isolate affected devices, and monitoring for suspicious network traffic patterns that may indicate exploitation attempts. The vulnerability aligns with ATT&CK technique T1059.001 command and scripting interpreter, specifically targeting the execution of system commands through web interfaces. Organizations should also consider implementing web application firewalls to detect and block malicious requests targeting the vulnerable script path. The flaw demonstrates poor input validation practices that should be addressed through comprehensive security testing of embedded web applications, particularly focusing on how user inputs are processed in server-side scripts. Network administrators should also verify that default credentials are changed and that remote management features are disabled when not required, as these configurations can compound the risk associated with command injection vulnerabilities. The affected devices represent a common class of embedded systems where web interfaces provide direct access to underlying system functionality, making proper input validation and sanitization critical for preventing such vulnerabilities.