CVE-2019-7579 in WRT1900ACS
Summary
by MITRE
An issue was discovered on Linksys WRT1900ACS 1.0.3.187766 devices. An ability exists for an unauthenticated user to browse a confidential ui/1.0.99.187766/dynamic/js/setup.js.localized file on the router's webserver, allowing for an attacker to identify possible passwords that the system uses to set the default guest network password. An attacker can use this list of 30 words along with a random 2 digit number to brute force their access onto a router's guest network.
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Analysis
by VulDB Data Team • 10/06/2023
The vulnerability identified in CVE-2019-7579 affects Linksys WRT1900ACS routers running firmware version 1.0.3.187766 and represents a critical information disclosure flaw that exposes sensitive configuration data through an improperly secured web interface. This vulnerability falls under the CWE-200 category of Information Exposure, where sensitive information is accessible to unauthorized parties without authentication. The flaw exists within the router's web server implementation, specifically in the handling of dynamic JavaScript files that contain default credential information. The exposed file ui/1.0.99.187766/dynamic/js/setup.js.localized contains a hardcoded list of 30 potential passwords that the system uses to generate default guest network credentials. This represents a fundamental failure in secure credential management practices and demonstrates poor separation of concerns in the router's web application architecture. The vulnerability is particularly concerning because it provides attackers with a targeted attack surface that significantly reduces the complexity of brute force attempts against guest network access.
The technical exploitation of this vulnerability occurs through a simple web request that bypasses authentication mechanisms entirely, allowing any remote attacker to access the sensitive JavaScript file without requiring valid credentials or network access privileges. This unauthenticated access pattern aligns with ATT&CK technique T1212, which involves accessing data through unauthorized access to system components. The exposed file contains a predetermined list of 30 words that, when combined with a random two-digit number, creates a predictable credential generation scheme for guest network passwords. This approach to credential generation violates security best practices and creates a known attack vector that can be systematically exploited. The vulnerability demonstrates a lack of proper input validation and output encoding in the web server's response handling, allowing for direct file system access to configuration files that should remain protected within the router's secure zones.
The operational impact of this vulnerability extends beyond simple credential theft, as it enables unauthorized network access and potentially provides attackers with additional attack vectors for further compromise. An attacker who successfully brute forces access to the guest network can establish a foothold within the network infrastructure, potentially leading to lateral movement and access to other network resources. This vulnerability creates a persistent threat that remains active until the firmware is updated, as the exposed file contains default credentials that are commonly used across multiple devices in the same product line. The attack surface is particularly dangerous because guest networks are often configured with less stringent security controls than primary network segments, making them attractive targets for initial access. This vulnerability also demonstrates the importance of secure configuration management and the risks associated with including hard-coded credentials in firmware releases, as it directly impacts network security posture and compliance with industry standards such as NIST SP 800-53.
The recommended mitigations for this vulnerability include immediate firmware updates from Linksys to address the exposed file access issue, along with network segmentation practices that limit access to guest networks and implement proper access controls. Organizations should also conduct vulnerability assessments to identify similar information disclosure vulnerabilities in other network devices and implement web application firewalls to prevent direct access to sensitive configuration files. The remediation process should include disabling guest network functionality if not required, implementing strong authentication mechanisms, and conducting regular security audits of network infrastructure components. Additionally, security teams should monitor for similar vulnerabilities in other router models and firmware versions, as this type of information disclosure often indicates broader architectural weaknesses in embedded web applications. The vulnerability highlights the critical need for secure development practices and proper security testing of network devices before deployment, particularly in environments where network access control is paramount for maintaining security boundaries and protecting sensitive data assets.