CVE-2019-18992 in OpenWrt
Summary
by MITRE
OpenWrt 18.06.4 allows XSS via these Name fields to the cgi-bin/luci/admin/network/firewall/rules URI: "Open ports on router" and "New forward rule" and "New Source NAT" (this can occur, for example, on a TP-Link Archer C7 device).
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Analysis
by VulDB Data Team • 03/05/2024
This vulnerability exists in OpenWrt version 18.06.4 where cross-site scripting attacks can be executed through the Name fields of specific firewall configuration pages. The affected URI path cgi-bin/luci/admin/network/firewall/rules contains three distinct input fields labeled "Open ports on router", "New forward rule", and "New Source NAT" that fail to properly sanitize user input before rendering it back to the browser. This represents a classic reflected cross-site scripting flaw that allows attackers to inject malicious scripts into the web interface, potentially compromising the router's administrative functionality and the network it protects.
The technical implementation of this vulnerability stems from insufficient input validation and output encoding within the LuCI web interface framework that OpenWrt utilizes for its administrative console. When users enter data into these Name fields and submit the firewall configuration forms, the system does not adequately escape special characters or validate the input against known XSS attack patterns. This failure to sanitize user-provided data creates an environment where malicious payloads can be executed within the context of the authenticated user's browser session, potentially enabling attackers to perform actions such as stealing session cookies, modifying firewall rules, or redirecting users to malicious sites.
The operational impact of this vulnerability extends beyond simple script execution as it provides attackers with a foothold within the router's administrative interface. Since the affected device is typically accessible from within the local network, attackers who gain access to the network can exploit this vulnerability to manipulate firewall configurations, potentially opening unauthorized access points or disabling security measures. This is particularly concerning for devices like the TP-Link Archer C7 which are commonly deployed in home and small office environments where network security is paramount. The vulnerability essentially allows an attacker to compromise the router's security posture and potentially gain access to the entire local network.
The vulnerability aligns with CWE-79 which specifically addresses cross-site scripting flaws in web applications. From an adversarial perspective, this vulnerability maps to ATT&CK technique T1059.007 for command and control through web shells and T1566 for initial access via web application attacks. The attack vector requires minimal privileges as the vulnerability is accessible through the standard web interface, making it particularly dangerous for unpatched devices. Organizations should implement immediate mitigations including applying the vendor-provided security patches, implementing network segmentation to limit access to administrative interfaces, and monitoring for suspicious activity in firewall configuration changes.
Security professionals should note that this vulnerability demonstrates the critical importance of input validation and output encoding in web application security. The flaw represents a failure in the principle of least privilege and proper data sanitization within the LuCI framework. Organizations should conduct comprehensive vulnerability assessments of their network infrastructure to identify other potentially affected OpenWrt installations and ensure proper patch management protocols are in place. The vulnerability also underscores the need for security awareness training for network administrators who may inadvertently introduce malicious payloads through web interface interactions.
The remediation approach should include immediate patching of OpenWrt systems to version 18.06.5 or later where this vulnerability has been addressed. Additionally, network administrators should implement additional security controls such as restricting access to the administrative interface to specific IP addresses, enabling two-factor authentication where possible, and regularly auditing firewall rule configurations for unauthorized changes. The vulnerability serves as a reminder that even seemingly benign administrative web interfaces can provide attackers with significant attack surface if proper security measures are not implemented throughout the application development lifecycle.