CVE-2008-2167 in ZyWALL 100
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in ZyXEL ZyWALL 100 allows remote attackers to inject arbitrary web script or HTML via the Referer header, which is not properly handled in a 404 Error page.
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Analysis
by VulDB Data Team • 02/13/2025
The vulnerability identified as CVE-2008-2167 represents a critical cross-site scripting flaw in ZyXEL ZyWALL 100 firewalls that exposes organizations to significant web-based attack vectors. This vulnerability specifically targets the device's handling of HTTP Referer headers during 404 error responses, creating an exploitable condition where malicious actors can inject arbitrary web scripts or HTML content. The issue stems from inadequate input validation and sanitization mechanisms within the firewall's error page generation process, which fails to properly escape or filter user-supplied data before rendering it in the browser context. The ZyWALL 100 series represents a popular line of network security appliances that many organizations rely upon for perimeter protection, making this vulnerability particularly concerning from a risk management perspective.
The technical exploitation of this vulnerability occurs when an attacker crafts a malicious Referer header value that contains embedded script code, then navigates to a non-existent URL on the firewall's web interface. When the device generates a 404 error page, it incorporates the unfiltered Referer header content directly into the HTML response without proper sanitization, allowing the injected script to execute in the context of a victim's browser session. This particular flaw maps directly to CWE-79, which defines Cross-Site Scripting vulnerabilities as weaknesses that occur when an application includes untrusted data in a new web page without proper validation or escaping, or without a security context that prevents the browser from interpreting the data as executable code. The vulnerability exists at the application layer and leverages the web interface's failure to implement proper output encoding for dynamic content.
The operational impact of this vulnerability extends beyond simple script injection, as it can enable attackers to perform session hijacking, steal administrative credentials, redirect users to malicious sites, or execute arbitrary commands within the browser context of authenticated users. Attackers can potentially leverage this vulnerability to establish persistent access to the firewall's administrative interface, compromising the entire network security infrastructure. The attack vector is particularly insidious because it requires no authentication to exploit and can be delivered through simple web navigation or email links, making it highly suitable for social engineering campaigns. From an attacker's perspective, this vulnerability aligns with ATT&CK technique T1059.007 for Command and Scripting Interpreter: JavaScript, and T1566 for Phishing, as it enables the delivery of malicious JavaScript payloads that can persist across user sessions and potentially escalate privileges within the network environment.
Organizations affected by this vulnerability should implement immediate mitigations including disabling unnecessary web interface access, implementing network segmentation to limit exposure, and applying vendor-provided patches or firmware updates when available. The firewall's web interface should be configured to use secure headers and implement Content Security Policy directives to prevent script execution from untrusted sources. Network administrators should also consider implementing web application firewalls or intrusion detection systems that can identify and block malicious Referer header patterns. Regular security assessments should include testing for similar input validation flaws in other network infrastructure components, as this vulnerability demonstrates a systemic issue with how legacy network appliances handle user-supplied data in error conditions. The vulnerability also highlights the importance of proper input sanitization and output encoding practices in network security devices, as these systems often serve as trusted gateways that require robust protection against web-based attacks that could compromise the entire network infrastructure.