CVE-2019-10040 in DIR-816 A2
Summary
by MITRE
The D-Link DIR-816 A2 1.11 router only checks the random token when authorizing a goform request. An attacker can get this token from dir_login.asp and use a hidden API URL /goform/SystemCommand to execute a system command without authentication.
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Analysis
by VulDB Data Team • 08/07/2023
The vulnerability identified as CVE-2019-10040 affects the D-Link DIR-816 A2 1.11 router firmware, representing a critical authentication bypass flaw that undermines the device's security model. This issue stems from insufficient authorization mechanisms within the router's web interface implementation, specifically in how the system validates user credentials during form submissions. The vulnerability exists because the router's authentication process relies solely on a random token validation without proper session management or user authentication verification, creating a fundamental weakness in the access control architecture.
The technical exploitation of this vulnerability occurs through a specific attack vector involving the extraction and reuse of authentication tokens. Attackers can obtain the random token by accessing the dir_login.asp page, which serves as an entry point for retrieving session identifiers used by the router's web interface. Once obtained, this token can be leveraged to construct malicious requests to the hidden API endpoint at /goform/SystemCommand, which executes system commands without requiring proper authentication. This represents a classic case of broken authentication where the system fails to implement proper session validation, allowing unauthorized command execution through token reuse.
The operational impact of this vulnerability extends beyond simple unauthorized access to encompass complete system compromise. An attacker with network access can execute arbitrary system commands with the privileges of the web server process, potentially leading to full device control, data exfiltration, or use as a pivot point for attacking other devices on the network. The presence of a hidden API endpoint without proper access controls creates an attack surface that violates standard security practices and represents a failure in the principle of least privilege. This vulnerability enables attackers to perform actions such as modifying router configurations, accessing network traffic, or installing malicious firmware, making it particularly dangerous in enterprise or home network environments.
This vulnerability maps directly to CWE-305 Authentication Bypass and CWE-306 Missing Authentication for Critical Function, both of which are categorized under the OWASP Top Ten 2017 as critical security weaknesses. From an ATT&CK framework perspective, this vulnerability enables multiple techniques including T1059 Command and Scripting Interpreter for executing system commands, T1071 Application Layer Protocol for web-based communication, and T1082 System Information Discovery for gathering device information. The attack chain follows T1190 Exploitation of Remote Services through the exploitation of a web interface vulnerability, ultimately leading to T1068 Exploitation for Privilege Escalation by leveraging the elevated privileges of the web server process.
Mitigation strategies for this vulnerability require immediate firmware updates from D-Link, as the issue stems from the router's implementation rather than configuration. Network administrators should implement network segmentation to limit access to affected devices, deploy intrusion detection systems to monitor for suspicious API requests, and consider disabling unnecessary web interfaces or API endpoints when not required. The recommended approach includes implementing proper authentication mechanisms with strong session management, using CSRF tokens in conjunction with proper session validation, and ensuring all API endpoints require proper authorization before executing privileged operations. Additionally, organizations should conduct regular vulnerability assessments of network devices and implement network access controls to prevent lateral movement if exploitation occurs. The vulnerability highlights the importance of proper security testing during development and the necessity of implementing defense-in-depth strategies to protect network infrastructure from such critical flaws.