CVE-2002-1599 in DansGuardian
Summary
by MITRE
DansGuardian before 2.4.5-1 allows remote attackers to bypass content filtering rules via hex-encoded URLs.
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Analysis
by VulDB Data Team • 11/18/2024
The vulnerability identified as CVE-2002-1599 affects DansGuardian versions prior to 2.4.5-1, representing a significant security flaw in web content filtering systems that can be exploited by remote attackers to circumvent established filtering policies. This issue specifically targets the URL parsing mechanism within DansGuardian, which is widely deployed in corporate and institutional environments to restrict access to inappropriate or malicious web content. The vulnerability stems from inadequate input validation and encoding handling within the proxy filtering software, creating a pathway for attackers to manipulate URL structures and evade content restrictions.
The technical implementation of this vulnerability involves the exploitation of hex-encoded URLs that are not properly sanitized or decoded before being processed by DansGuardian's filtering engine. When a remote attacker submits a URL containing hexadecimal encoding such as %20 for spaces or other encoded characters, the older versions of DansGuardian fail to properly decode these sequences before applying filtering rules. This processing gap allows malicious users to craft URLs that appear to comply with filtering policies while actually containing content that should be blocked. The flaw operates at the application layer and can be executed without requiring authentication or elevated privileges, making it particularly dangerous in environments where DansGuardian serves as the primary content filtering mechanism.
The operational impact of CVE-2002-1599 extends beyond simple bypass of content restrictions, potentially exposing organizations to various security risks including access to malicious websites, data exfiltration attempts, and unauthorized access to restricted resources. Organizations relying on DansGuardian for network security may unknowingly allow malicious actors to circumvent their established filtering policies, undermining the effectiveness of their cybersecurity posture. This vulnerability particularly affects environments with strict content filtering requirements such as schools, libraries, corporate networks, and government institutions where maintaining controlled access to web resources is critical. The remote nature of the exploit means that attackers can leverage this vulnerability from outside the network perimeter, making it especially concerning for organizations with limited network segmentation.
Mitigation strategies for this vulnerability require immediate deployment of DansGuardian version 2.4.5-1 or later, which includes proper URL decoding and validation mechanisms that address the encoding bypass issue. Organizations should also implement additional monitoring and logging mechanisms to detect unusual URL patterns or attempted bypass attempts. Network administrators should consider implementing supplementary security controls such as deep packet inspection, web application firewalls, or additional proxy filtering solutions to provide defense-in-depth. The vulnerability aligns with CWE-116, which addresses improper encoding or escaping of output, and maps to attack techniques in the ATT&CK framework under T1071.004 for application layer protocol and T1059.007 for command and scripting interpreter. Regular security assessments and vulnerability scanning should be conducted to ensure that all filtering systems remain up to date with the latest security patches and that proper input validation mechanisms are in place to prevent similar encoding-related vulnerabilities from occurring in other components of the network security infrastructure.