CVE-2018-20057 in DIR-605L
Summary
by MITRE
An issue was discovered in /bin/boa on D-Link DIR-619L Rev.B 2.06B1 and DIR-605L Rev.B 2.12B1 devices. goform/formSysCmd allows remote authenticated users to execute arbitrary OS commands via the sysCmd POST parameter.
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Analysis
by VulDB Data Team • 04/19/2020
The vulnerability identified as CVE-2018-20057 represents a critical command injection flaw in the web interface of D-Link wireless routers, specifically affecting models DIR-619L and DIR-605L with particular firmware versions. This security weakness exists within the /bin/boa binary component that serves as the web server for these devices, creating an avenue for attackers to execute malicious operating system commands remotely. The vulnerability stems from inadequate input validation and sanitization within the goform/formSysCmd endpoint, which processes system commands submitted through the sysCmd POST parameter.
The technical implementation of this flaw involves a classic command injection vulnerability where user-supplied input directly influences system command execution without proper sanitization. When an authenticated user submits a crafted sysCmd parameter through the POST request, the application fails to properly escape or validate the input before incorporating it into system calls. This creates a scenario where malicious payloads can be executed with the privileges of the web server process, typically running with elevated system permissions. The vulnerability is classified as CWE-77 according to the CWE standard, which specifically addresses command injection flaws where untrusted data is incorporated into system commands without proper validation or escaping mechanisms.
The operational impact of this vulnerability extends beyond simple command execution, as it provides attackers with potential access to sensitive system information and the ability to manipulate network configurations. An attacker who gains authenticated access to the device can leverage this flaw to execute arbitrary commands that may include system reconnaissance, data exfiltration, network scanning, or even payload delivery for further exploitation. The vulnerability affects devices running firmware versions 2.06B1 and 2.12B1 respectively, indicating that this was a persistent issue across multiple revisions of the affected product lines. The remote authenticated nature of the attack means that an attacker does not need physical access to the device but only requires valid credentials to the router's web interface.
From a cybersecurity perspective, this vulnerability aligns with ATT&CK technique T1059.001 for command and scripting interpreter, specifically targeting the execution of system commands through web interfaces. The flaw essentially provides a backdoor execution path that bypasses normal authentication and authorization mechanisms, allowing for privilege escalation and persistent access to network infrastructure. Organizations with these vulnerable devices face significant risks including potential network compromise, unauthorized access to connected systems, and exposure of sensitive network information. The attack surface is particularly concerning given that many users may not regularly update their router firmware, leaving these devices perpetually vulnerable to exploitation.
Mitigation strategies for this vulnerability require immediate firmware updates from D-Link, which should include proper input validation and sanitization of all user-supplied parameters. Network administrators should also implement network segmentation to limit access to these devices, enforce strong authentication mechanisms, and monitor for suspicious network activity that may indicate exploitation attempts. Additionally, implementing web application firewalls and intrusion detection systems can help identify and block malicious command injection attempts. The vulnerability demonstrates the critical importance of input validation in web applications and highlights the need for regular security assessments of network infrastructure components that may be exposed to remote access.