CVE-2019-17224 in Broadband CH7465LG Modem
Summary
by MITRE
The web interface of the Compal Broadband CH7465LG modem (version CH7465LG-NCIP-6.12.18.25-2p6-NOSH) is vulnerable to a /%2f/ path traversal attack, which can be exploited in order to test for the existence of a file pathname outside of the web root directory. If a file exists but is not part of the product, there is a 404 error. If a file does not exist, there is a 302 redirect to index.html.
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Analysis
by VulDB Data Team • 01/29/2024
The CVE-2019-17224 vulnerability represents a critical path traversal flaw in the web interface of Compal Broadband CH7465LG modems, specifically affecting firmware version CH7465LG-NCIP-6.12.18.25-2p6-NOSH. This vulnerability stems from inadequate input validation within the web application's file handling mechanisms, allowing remote attackers to manipulate URI paths through encoded forward slashes represented as %2f. The flaw enables attackers to probe the underlying filesystem by constructing malicious requests that bypass normal directory restrictions and attempt to access files outside the designated web root directory. The vulnerability specifically leverages the improper handling of URL-encoded path separators, which should normally be rejected or properly normalized by the web server before file access operations are initiated.
The technical implementation of this vulnerability operates through the exploitation of the web application's insufficient sanitization of user-supplied input in URI parameters. When a request containing encoded path traversal sequences is submitted to the modem's web interface, the application fails to properly validate or normalize the input before performing file system operations. This allows attackers to craft requests that effectively navigate to arbitrary locations within the device's file system hierarchy. The vulnerability is particularly concerning because it provides a testing mechanism that reveals file system structure information through different HTTP response codes - a 404 error indicates the existence of a file outside the web root, while a 302 redirect to index.html suggests the file does not exist. This differential response behavior creates a reconnaissance opportunity for attackers to map the device's internal file structure without requiring authentication.
The operational impact of CVE-2019-17224 extends beyond simple information disclosure, as it provides attackers with a foundation for further exploitation attempts. The vulnerability can be categorized under CWE-22 Path Traversal and aligns with attack patterns described in the MITRE ATT&CK framework under T1213 Data from Information Repositories. The ability to test for file existence outside the web root directory enables attackers to identify sensitive files such as configuration files, credentials, or system binaries that might be accessible through the compromised web interface. This reconnaissance capability can lead to more sophisticated attacks including privilege escalation, system compromise, or the discovery of additional vulnerabilities within the device's software stack. The vulnerability affects not only the immediate device but also represents a potential gateway for network-wide attacks if the modem serves as a network gateway or router.
Security mitigations for CVE-2019-17224 should focus on implementing proper input validation and sanitization mechanisms within the web application layer. Organizations should immediately apply firmware updates from Compal Broadband if available, as this vulnerability typically requires vendor-provided patches to address the underlying code flaws. Network segmentation and access control measures should be implemented to restrict access to the modem's web interface to authorized personnel only, while disabling unnecessary web services. The implementation of web application firewalls and intrusion detection systems can help detect and prevent exploitation attempts by monitoring for suspicious URI patterns containing encoded path traversal sequences. Additionally, regular security assessments should include testing for similar path traversal vulnerabilities in other network devices and applications, as this type of flaw commonly affects embedded web interfaces in networking equipment and IoT devices. The vulnerability highlights the importance of proper input validation and secure coding practices in embedded systems, particularly those handling user input through web interfaces.