CVE-2004-2282 in DansGuardian
Summary
by MITRE
DansGuardian before 2.7.7-2 allows remote attackers to bypass URL filters via a ".." in the request.
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Analysis
by VulDB Data Team • 06/25/2018
The vulnerability identified as CVE-2004-2282 affects DansGuardian versions prior to 2.7.7-2, representing a significant security flaw in web content filtering systems that can be exploited by remote attackers to circumvent URL filtering mechanisms. This issue stems from inadequate input validation and path traversal handling within the application's processing of HTTP requests. The specific exploitation vector involves inserting double dots ".." into URL requests, which can manipulate the filtering system's interpretation of file paths and potentially allow access to restricted content. The vulnerability is classified as a path traversal attack, where attackers can manipulate directory paths to access resources outside the intended scope of the filtering system. This type of vulnerability is particularly dangerous in enterprise environments where DansGuardian is deployed to enforce web usage policies and prevent access to malicious or inappropriate content. The flaw demonstrates a critical weakness in the application's security architecture, specifically in how it handles URL parsing and validation before applying filter rules.
The technical implementation of this vulnerability exploits the way DansGuardian processes HTTP requests containing directory traversal sequences. When a request includes ".." characters, the filtering system fails to properly sanitize or validate these sequences, allowing them to be interpreted as parent directory references in file path resolution. This misconfiguration enables attackers to craft URLs that bypass the intended filtering logic by navigating through directory structures that should be restricted. The vulnerability operates at the application layer and requires no special privileges to exploit, making it particularly dangerous as it can be leveraged by anyone with network access to the filtering system. The flaw represents a failure in proper input sanitization and validation, which are fundamental security practices that should be implemented at all levels of application processing. This vulnerability type falls under the CWE-22 category for Path Traversal and aligns with ATT&CK technique T1071.004 for Application Layer Protocol: DNS, as it exploits weaknesses in application-level protocols and filtering mechanisms.
The operational impact of this vulnerability extends beyond simple bypass of content filters, potentially exposing organizations to significant security risks including access to malicious websites, data leakage, and violation of corporate policies. Organizations relying on DansGuardian for web content filtering may unknowingly allow users to access restricted resources, including phishing sites, malware distribution points, or inappropriate content that violates acceptable use policies. The vulnerability undermines the core security function of the filtering system, creating a false sense of security for administrators who may believe their content filtering is working correctly. Attackers can leverage this weakness to access restricted corporate resources or bypass monitoring systems that depend on the filtering appliance to maintain security posture. The exploitation of this vulnerability can lead to compliance violations in regulated environments where content filtering is mandated by industry standards and government regulations. Additionally, the vulnerability can be combined with other attack vectors to create more sophisticated attacks that exploit the bypassed filtering mechanisms. Organizations should consider this vulnerability as a critical issue requiring immediate remediation, as it fundamentally compromises the security controls provided by the filtering system.
The recommended mitigation strategy involves upgrading to DansGuardian version 2.7.7-2 or later, which includes proper input validation and sanitization to prevent directory traversal sequences from bypassing URL filtering. Organizations should also implement additional monitoring and logging to detect unusual URL patterns that may indicate exploitation attempts. Network segmentation and firewall rules should be configured to limit access to the filtering system to authorized administrators only, reducing the attack surface. Regular security assessments should be conducted to identify similar vulnerabilities in other filtering systems and web applications. Implementing web application firewalls and additional input validation mechanisms can provide defense in depth against similar path traversal attacks. Security teams should also establish incident response procedures for detecting and responding to exploitation attempts of this nature, including monitoring for suspicious URL patterns and conducting regular vulnerability assessments of content filtering infrastructure. The vulnerability serves as a reminder of the critical importance of proper input validation and the need for regular security updates in all network security appliances and applications.