CVE-2000-0853 in YaBB
Summary
by MITRE
YaBB Bulletin Board 9.1.2000 allows remote attackers to read arbitrary files via a .. (dot dot) attack.
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Analysis
by VulDB Data Team • 10/12/2025
The vulnerability identified as CVE-2000-0853 represents a classic directory traversal flaw affecting YaBB Bulletin Board version 9.1.2000. This security weakness enables remote attackers to access files outside the intended directory structure through manipulation of directory path references. The vulnerability stems from insufficient input validation and improper sanitization of user-supplied data that is used to construct file paths within the application's file handling mechanisms. When users provide directory path references containing double dot sequences, the application fails to properly validate or sanitize these inputs, allowing unauthorized access to arbitrary files on the server filesystem.
This directory traversal vulnerability operates by exploiting the way the bulletin board software processes file requests. Attackers can construct malicious URLs or input parameters that include sequences such as "../" or "..\..\" to navigate upward through the directory hierarchy. The flaw exists because the application does not adequately filter or validate path components before using them to access files, creating a pathway for attackers to bypass normal access controls and retrieve sensitive information from the server. The vulnerability is particularly dangerous because it can potentially allow access to configuration files, database credentials, user information, and other sensitive data stored on the same server hosting the bulletin board.
The operational impact of this vulnerability extends beyond simple information disclosure, as it can lead to complete system compromise if attackers gain access to critical system files or configuration data. The attack vector requires no special privileges or authentication, making it particularly dangerous for publicly accessible bulletin board systems. Security professionals should note that this vulnerability aligns with CWE-22, which describes improper limitation of a pathname to a restricted directory, commonly known as path traversal or directory traversal attacks. The attack pattern itself is catalogued in the MITRE ATT&CK framework under the technique of "Path Traversal" within the credential access and privilege escalation domains, highlighting its potential for escalating privileges and accessing restricted system resources.
Mitigation strategies for CVE-2000-0853 involve implementing robust input validation and sanitization mechanisms within the application code. Developers should ensure that all user-supplied input used in file path construction is properly validated and filtered to prevent directory traversal sequences from being processed. The recommended approach includes implementing strict path validation that rejects any input containing parent directory references or other potentially malicious path components. Additionally, system administrators should consider implementing proper access controls and file permissions to limit the exposure of sensitive files even if such attacks were to succeed. The most effective long-term solution involves upgrading to a patched version of YaBB Bulletin Board or migrating to a more modern, secure bulletin board system that properly implements input validation and follows secure coding practices to prevent such vulnerabilities from occurring in the first place.