CVE-2018-17786 in DIR-823G
Summary
by MITRE
On D-Link DIR-823G devices, ExportSettings.sh, upload_settings.cgi, GetDownLoadSyslog.sh, and upload_firmware.cgi do not require authentication, which allows remote attackers to execute arbitrary code.
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Analysis
by VulDB Data Team • 03/29/2020
The vulnerability identified as CVE-2018-17786 affects D-Link DIR-823G wireless routers and represents a critical authentication bypass flaw that exposes multiple administrative scripts to unauthenticated remote execution. This vulnerability resides in the device's web interface implementation where several key system scripts lack proper access controls, creating a pathway for malicious actors to gain unauthorized administrative privileges. The affected components include ExportSettings.sh, upload_settings.cgi, GetDownLoadSyslog.sh, and upload_firmware.cgi, all of which are designed to handle sensitive system operations but fail to validate user credentials before execution. The flaw stems from improper input validation and access control mechanisms within the router's firmware, specifically in the web server component that processes HTTP requests for these administrative functions.
The technical exploitation of this vulnerability allows remote attackers to execute arbitrary code on the affected device by directly accessing these unauthenticated endpoints without requiring any prior login credentials. This authentication bypass creates a severe security risk as it enables attackers to perform system-level operations including but not limited to configuration changes, firmware updates, log file retrieval, and system settings exports. The vulnerability maps directly to CWE-287 which describes improper authentication issues in software systems, and aligns with ATT&CK technique T1059.007 for command and scripting interpreter, as attackers can leverage these endpoints to execute shell commands on the target device. The affected scripts typically process user input through CGI interfaces, creating potential injection vectors for command execution attacks.
Operationally, this vulnerability presents significant risks to network security and device integrity as it allows attackers to compromise the entire router without requiring physical access or valid credentials. The impact extends beyond individual device compromise to potentially affect entire network infrastructures, as compromised routers can serve as entry points for lateral movement within local networks. Attackers can use the vulnerability to establish persistent backdoors, modify firewall rules, redirect traffic, or extract sensitive information from system logs. The exposure of firmware upload functionality particularly increases the risk of malicious firmware installation, potentially leading to complete device takeover. Network administrators may remain unaware of the compromise since the attacks can occur without generating obvious alerts, making this vulnerability particularly dangerous for enterprise and home network environments.
Mitigation strategies for CVE-2018-17786 require immediate action including firmware updates from D-Link, which should address the authentication bypass issues in the affected scripts. Network segmentation and firewall rules should be implemented to restrict access to router administrative interfaces from untrusted networks, while also limiting access to only necessary internal systems. Regular security audits should verify that administrative endpoints require proper authentication and that no unnecessary services are exposed to external networks. Device monitoring should include detection of unusual traffic patterns or unauthorized access attempts to router management interfaces, and network administrators should consider implementing intrusion detection systems to identify exploitation attempts. The vulnerability highlights the importance of secure coding practices and proper access control implementation, with recommendations aligning with NIST SP 800-53 security controls for access control and system configuration management.