CVE-2020-21016 in DIR-846
Summary
by MITRE • 10/31/2022
D-Link DIR-846 devices with firmware 100A35 allow remote attackers to execute arbitrary code as root via HNAP1/control/SetGuestWLanSettings.php.
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Analysis
by VulDB Data Team • 11/26/2022
The D-Link DIR-846 router series represents a popular consumer-grade networking device that has been found to contain a critical remote code execution vulnerability in its firmware version 100A35. This vulnerability specifically affects the HNAP1 protocol implementation within the device's web interface, which is used for remote management and configuration of network settings. The vulnerability exists within the SetGuestWLanSettings.php endpoint, which is part of the Home Network Administration Protocol version 1 implementation that allows external systems to manage router settings programmatically.
The technical flaw stems from inadequate input validation and sanitization within the guest wireless network settings configuration handler. When remote attackers send specially crafted HTTP requests to the vulnerable endpoint, the device fails to properly validate or sanitize user-supplied parameters before processing them. This allows malicious actors to inject arbitrary commands that are subsequently executed with root privileges on the underlying operating system. The vulnerability is particularly dangerous because it does not require authentication, making it accessible to anyone who can reach the device's network interface.
The operational impact of this vulnerability extends beyond simple unauthorized access to encompass complete system compromise and potential network infiltration. Attackers who exploit this vulnerability can gain root access to the router, enabling them to modify network configurations, install malicious software, redirect traffic, or establish persistent backdoors. The compromised device can then serve as a pivot point for attacking other systems within the local network, potentially leading to broader security breaches. This vulnerability particularly affects enterprise and home users who may not regularly update their firmware, leaving them exposed to automated exploitation attempts.
Mitigation strategies should focus on immediate firmware updates from D-Link to address the identified vulnerability, as well as network-level security controls such as firewall rules that restrict access to the affected web interface. Organizations should implement network segmentation to limit the potential impact of a compromised device and deploy intrusion detection systems to monitor for suspicious activity. The vulnerability aligns with CWE-77 and CWE-78 categories related to command injection and improper input sanitization, and maps to ATT&CK techniques including T1059 for command and script injection and T1021 for remote services. Regular security assessments and network monitoring are essential to identify and remediate similar vulnerabilities in networking infrastructure components.