CVE-2008-4918 in SonicOS
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in SonicWALL SonicOS Enhanced before 4.0.1.1, as used in SonicWALL Pro 2040 and TZ 180 and 190, allows remote attackers to inject arbitrary web script or HTML into arbitrary web sites via a URL to a site that is blocked based on content filtering, which is not properly handled in the CFS block page, aka "universal website hijacking."
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Analysis
by VulDB Data Team • 12/11/2024
This cross-site scripting vulnerability exists in SonicWALL SonicOS Enhanced versions prior to 4.0.1.1 affecting models including the Pro 2040 and TZ 180 and 190 firewalls. The flaw occurs when content filtering blocks access to certain websites and displays a CFS (Content Filtering Service) block page to users. The vulnerability stems from improper handling of user input within the block page generation process, allowing malicious actors to inject arbitrary web scripts or HTML content. This represents a critical security flaw that enables attackers to perform universal website hijacking by exploiting the content filtering mechanism. The vulnerability falls under CWE-79 which specifically addresses cross-site scripting flaws where untrusted data is improperly incorporated into web pages without proper validation or encoding. From an operational perspective, this vulnerability creates a significant risk as it allows remote attackers to execute malicious code within the context of a user's browser session, potentially leading to session hijacking, credential theft, or redirection to malicious sites.
The technical implementation of this vulnerability exploits the way the firewall handles URLs that are blocked by content filtering policies. When a user attempts to access a blocked website, the firewall generates a block page that should display information about the blocked content. However, the CFS block page fails to properly sanitize or encode user-provided input, creating an XSS vector. Attackers can craft malicious URLs that, when processed by the firewall's content filtering system, get reflected back to users in the block page without proper security measures. This creates a persistent vector where any user who attempts to access the malicious URL will encounter the injected script during the block page rendering process. The attack can be executed without requiring authentication or specific privileges, making it particularly dangerous in enterprise environments where users frequently access the internet through content-filtering firewalls. This vulnerability aligns with ATT&CK technique T1566 which covers social engineering tactics involving malicious content delivery, and specifically T1566.001 for spearphishing with malicious attachments or links.
The operational impact of CVE-2008-4918 extends beyond simple script injection, as it enables sophisticated attack chains that can compromise entire user sessions. An attacker could inject a script that steals browser cookies, redirects users to phishing sites, or even delivers malware payloads through drive-by downloads. The universal nature of the vulnerability means that any website that is blocked by the firewall's content filtering could become a vector for attack, creating a broad attack surface that affects all users within the network. Organizations using affected SonicWALL models face significant risk of credential theft, data exfiltration, and unauthorized access to internal resources. The vulnerability also undermines the trust model of the firewall's content filtering system, as users may unknowingly interact with malicious content while attempting to access legitimate websites. This type of vulnerability demonstrates the critical importance of input validation in web applications, particularly in security appliances where the system's integrity directly impacts network security. The flaw represents a fundamental failure in secure coding practices where output encoding and input sanitization were not properly implemented in the firewall's web interface components.
Mitigation strategies for this vulnerability require immediate patching of affected SonicWALL appliances to version 4.0.1.1 or later, which contains the necessary security fixes for the XSS flaw in the CFS block page handling. Network administrators should also implement additional monitoring to detect suspicious content filtering activities and verify that all firewall models in the environment are updated to supported versions. Organizations should consider implementing network segmentation to limit the impact of potential exploitation and ensure that content filtering policies are regularly reviewed and tested. The vulnerability highlights the importance of maintaining up-to-date security appliances and demonstrates how even minor security flaws in network infrastructure can create significant attack vectors. Security teams should also conduct regular vulnerability assessments of their network security equipment and establish processes for rapid patch deployment. The incident underscores the need for comprehensive security testing of web interfaces in network appliances and proper implementation of secure coding practices that prevent XSS vulnerabilities in all user-facing components. Regular security audits should include assessment of content filtering and web interface components to identify similar vulnerabilities that could be exploited in a similar manner.