CVE-2006-4161 in XennoBB
Summary
by MITRE
Directory traversal vulnerability in the avatar_gallery action in profile.php in XennoBB 2.1.0 and earlier allows remote attackers to read arbitrary files via a .. (dot dot) in the category parameter.
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Analysis
by VulDB Data Team • 08/02/2018
The vulnerability identified as CVE-2006-4161 represents a critical directory traversal flaw within the XennoBB 2.1.0 bulletin board software, specifically affecting the avatar_gallery functionality within profile.php. This security weakness stems from inadequate input validation mechanisms that fail to properly sanitize user-supplied data before processing. The vulnerability manifests when the category parameter receives a .. (dot dot) sequence, which allows attackers to navigate outside the intended directory structure and access arbitrary files on the server filesystem. Such directory traversal vulnerabilities fall under the common weakness enumeration CWE-22, which categorizes improper limitation of a pathname to a restricted directory, also known as path traversal or directory traversal.
The technical implementation of this vulnerability exploits the lack of proper input sanitization in the profile.php script where the avatar_gallery action processes user input without adequate validation or filtering. When an attacker submits a malicious category parameter containing directory traversal sequences, the application fails to properly validate or sanitize this input before using it in file operations. This allows the attacker to craft requests that can traverse directories beyond the intended scope, potentially accessing sensitive files such as configuration files, database credentials, or other system files that should remain protected from unauthorized access. The attack vector is particularly dangerous because it requires no authentication and can be executed remotely, making it a significant threat to web application security.
The operational impact of this vulnerability extends beyond simple file disclosure, as it can provide attackers with substantial information gathering capabilities and potentially lead to complete system compromise. An attacker can leverage this vulnerability to access critical system files, configuration data, and potentially sensitive user information stored within the application's directory structure. The vulnerability affects all versions of XennoBB up to and including 2.1.0, representing a widespread issue within the software ecosystem. According to ATT&CK framework, this vulnerability maps to T1083 (File and Directory Discovery) and T1566 (Phishing with Malicious Attachments) as attackers can use the discovered files to further their attack objectives. The vulnerability's remote exploitability means that attackers can target the application from outside the network perimeter without requiring local system access or credentials.
Mitigation strategies for CVE-2006-4161 should focus on immediate input validation and sanitization measures within the profile.php script. The most effective approach involves implementing strict input validation that filters out or rejects any sequences containing .. or similar directory traversal patterns before processing user input. Additionally, developers should implement proper access controls that restrict file access to only intended directories and employ secure coding practices such as using allowlists for valid directory paths rather than relying on user input for file operations. The vulnerability demonstrates the critical importance of input validation and the principle of least privilege in web application security. Organizations using affected versions of XennoBB should upgrade to patched versions immediately, as the vulnerability has been known since 2006 and represents a fundamental security flaw that can be exploited for complete system compromise. Security monitoring should include detection of suspicious directory traversal attempts in web application logs, and network intrusion detection systems should be configured to alert on patterns consistent with this type of attack.