CVE-2003-0156 in LXR
Summary
by MITRE
Directory traversal vulnerability in Cross-Referencing Linux (LXR) allows remote attackers to read arbitrary files via .. (dot dot) sequences in the v parameter.
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Analysis
by VulDB Data Team • 08/24/2025
The CVE-2003-0156 vulnerability represents a classic directory traversal flaw within the Cross-Referencing Linux (LXR) system, a web-based tool designed to provide interactive browsing of source code repositories. This vulnerability specifically affects the parameter handling mechanism within LXR's web interface, where user input is not properly sanitized before being used to construct file paths. The flaw manifests when the v parameter, which typically specifies the file or directory to be displayed, accepts directory traversal sequences such as .. (dot dot) that allow attackers to navigate outside the intended directory structure and access arbitrary files on the server filesystem.
The technical implementation of this vulnerability stems from inadequate input validation and path construction logic within the LXR application. When a user requests a specific file or directory through the web interface, the application constructs a file path by directly incorporating user-supplied parameters into the filesystem access operations. This practice violates fundamental security principles and creates an opportunity for attackers to manipulate the path resolution process. The .. sequences enable attackers to move up directory levels, potentially accessing sensitive system files, configuration data, or source code that should remain restricted. This type of vulnerability falls under the CWE-22 category of Improper Limiting of a Pathname to a Restricted Directory, which is classified as a path traversal attack vector.
The operational impact of this vulnerability extends beyond simple information disclosure, as it provides attackers with the capability to access critical system resources that may contain sensitive data such as passwords, configuration files, or source code that could reveal additional attack vectors. An attacker could leverage this vulnerability to access system files like /etc/passwd, /etc/shadow, or other sensitive configuration data that might contain credentials or system information useful for further exploitation. The vulnerability is particularly concerning in environments where LXR is used to index and display source code repositories that may contain proprietary information or sensitive implementation details. This weakness enables attackers to potentially gain unauthorized access to source code that could reveal implementation flaws, security configurations, or other sensitive information that could be exploited in subsequent attacks.
Mitigation strategies for CVE-2003-0156 should focus on implementing proper input validation and sanitization mechanisms within the LXR application. The most effective approach involves implementing strict parameter validation that rejects or removes directory traversal sequences before they are used in file path construction operations. This can be achieved through the implementation of a whitelist-based validation approach that only allows specific, safe characters and patterns in user input. Additionally, the application should employ proper path normalization and validation techniques that ensure all file access operations occur within the intended directory boundaries. Organizations should also consider implementing web application firewalls that can detect and block suspicious path traversal patterns, as well as conducting regular security audits of web applications to identify and remediate similar vulnerabilities. The remediation efforts should align with the principles outlined in the OWASP Top Ten and the ATT&CK framework's T1083 (File and Directory Discovery) technique, which emphasizes the importance of preventing unauthorized file access through proper input validation and access control mechanisms.