CVE-2019-19229 in Solar Inverter
Summary
by MITRE
admincgi-bin/service.fcgi on Fronius Solar Inverter devices before 3.14.1 (HM 1.12.1) allows action=download&filename= Directory Traversal.
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Analysis
by VulDB Data Team • 03/07/2024
The vulnerability identified as CVE-2019-19229 affects Fronius Solar Inverter devices running firmware versions prior to 3.14.1, specifically impacting the admincgi-bin/service.fcgi component. This represents a critical directory traversal flaw that enables unauthorized access to sensitive system files through a carefully crafted web request. The vulnerability exists within the web interface of these solar energy monitoring devices, which are widely deployed in residential and commercial solar installations, making them attractive targets for cybercriminals seeking to compromise renewable energy infrastructure.
The technical implementation of this vulnerability stems from inadequate input validation within the service.fcgi script which processes administrative requests. When the application receives a request containing action=download&filename= parameters, it fails to properly sanitize the filename input before using it in file system operations. This allows attackers to manipulate the filename parameter to traverse directories and access files outside the intended web root directory. The flaw specifically enables access to system files, configuration data, and potentially sensitive operational information that should remain restricted to authorized administrative users. The vulnerability operates at the application layer and can be exploited through standard web browser interactions without requiring specialized tools or deep system knowledge.
The operational impact of this vulnerability extends beyond simple information disclosure, as it provides attackers with the ability to potentially extract system configuration details, user credentials, and operational parameters that could be used for further attacks. Solar inverter systems contain critical operational data including power generation metrics, device identifiers, and network configuration information that could be valuable for attackers planning more sophisticated attacks against the broader energy infrastructure. The vulnerability affects devices that are typically deployed in remote locations and may have limited network monitoring, making detection and response more challenging. According to CWE-22, this vulnerability maps directly to directory traversal issues where insufficient input validation allows attackers to access files outside the intended directory structure, a well-documented weakness in web application security.
Security professionals should note that this vulnerability aligns with several ATT&CK framework techniques including T1083 (File and Directory Discovery) and T1566 (Phishing for Information) as attackers could use the discovered information to plan more targeted attacks against the broader network infrastructure. The affected devices typically operate in environments with limited security monitoring and may be managed through web interfaces that lack robust authentication mechanisms, amplifying the risk. Organizations should implement immediate mitigations including firmware updates to version 3.14.1 or later, network segmentation to isolate these devices from critical systems, and enhanced monitoring of web traffic to these components. The vulnerability demonstrates the importance of securing industrial control systems and IoT devices that are often deployed with minimal security considerations, highlighting the need for comprehensive security assessments of operational technology infrastructure.