CVE-2001-0123 in BPS Forum
Summary
by MITRE
Directory traversal vulnerability in eXtropia bbs_forum.cgi 1.0 allows remote attackers to read arbitrary files via a .. (dot dot) attack on the file parameter.
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Analysis
by VulDB Data Team • 10/08/2025
The vulnerability identified as CVE-2001-0123 represents a classic directory traversal flaw within the eXtropia bbs_forum.cgi version 1.0 web application. This security weakness resides in the improper validation of user-supplied input parameters, specifically the file parameter that governs file operations within the bulletin board system. The vulnerability stems from the application's failure to adequately sanitize or filter input data before processing file system operations, creating an exploitable condition that allows malicious actors to navigate beyond the intended directory structure.
This directory traversal vulnerability operates through the manipulation of directory path references using the double dot sequence .. which is a standard method for accessing parent directories in Unix-like and Windows file systems. When the bbs_forum.cgi script processes the file parameter without proper input validation, attackers can append sequences of .. characters to access files outside the designated web root or application directory boundaries. The flaw essentially permits arbitrary file reading capabilities, enabling attackers to retrieve sensitive information from the server's file system including configuration files, user data, and potentially system files that should remain protected.
The operational impact of this vulnerability extends beyond simple information disclosure, as it provides attackers with the ability to access critical system resources that could lead to further compromise. An attacker could potentially read sensitive files such as password databases, configuration files containing database credentials, or application source code that might reveal additional vulnerabilities. The vulnerability's remote exploitability means that an attacker does not need physical access to the system or local network privileges to leverage this flaw, making it particularly dangerous in internet-facing applications. This weakness aligns with CWE-22, which specifically addresses improper limitation of a pathname to a restricted directory, commonly known as path traversal or directory traversal vulnerabilities.
From a threat modeling perspective, this vulnerability fits within the attack pattern category of file system manipulation and information disclosure, typically categorized under the MITRE ATT&CK framework's T1005 (Data from Local System) and T1083 (File and Directory Discovery) techniques. The vulnerability's exploitation requires minimal technical skill and can be automated, making it attractive to both automated scanners and less sophisticated attackers. The impact is particularly severe in environments where the web application runs with elevated privileges or where sensitive data is stored in accessible locations within the file system hierarchy.
The recommended mitigations for this vulnerability involve implementing proper input validation and sanitization mechanisms that filter or reject potentially dangerous sequences such as .. or similar path traversal patterns. Applications should employ a whitelist approach for file operations, explicitly defining which files or directories are accessible and rejecting any input that attempts to reference paths outside of these defined boundaries. Additionally, the application should run with minimal required privileges and implement proper access controls to ensure that even if traversal occurs, the attacker cannot access sensitive system resources. The fix should also include implementing proper directory traversal prevention techniques such as canonicalizing file paths and ensuring that all file operations occur within a designated safe directory structure. Organizations should also consider implementing web application firewalls and input validation rules to detect and prevent such attacks at the network perimeter.