CVE-2006-0891 in NOCC
Summary
by MITRE
Multiple directory traversal vulnerabilities in NOCC Webmail 1.0 allow remote attackers to include arbitrary files via .. (dot dot) sequences and a trailing NULL (%00) byte in (1) the _SESSION['nocc_theme'] parameter in (a) html/footer.php; and (2) the lang and (3) theme parameters and the (4) Accept-Language HTTP header field, when force_default_lang is disabled, in (b) index.php, as demonstrated by injecting PHP code into a profile and accessing it using the lang parameter in index.php.
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Analysis
by VulDB Data Team • 05/14/2025
The CVE-2006-0891 vulnerability represents a critical directory traversal flaw in NOCC Webmail 1.0 that exposes the application to remote code execution through manipulated file inclusion parameters. This vulnerability stems from insufficient input validation and sanitization mechanisms within the web application's core components, specifically affecting the session management and language/theme configuration handling systems. The flaw allows attackers to manipulate file paths through directory traversal sequences combined with null byte injection, creating a pathway for arbitrary file inclusion attacks that can ultimately lead to complete system compromise.
The technical implementation of this vulnerability occurs through multiple attack vectors within the webmail application's codebase. In the html/footer.php component, the _SESSION['nocc_theme'] parameter accepts user-supplied input without proper validation, allowing attackers to inject .. sequences that traverse up the directory tree to access files outside the intended web root. Additionally, the index.php file contains three distinct vulnerable parameters including lang, theme, and Accept-Language HTTP header fields that all accept unvalidated user input when force_default_lang is disabled. The combination of these vulnerabilities creates a multi-layered attack surface where an attacker can manipulate the application's file inclusion logic through crafted null byte sequences, effectively bypassing normal file access controls and potentially executing malicious PHP code.
The operational impact of this vulnerability extends far beyond simple information disclosure, as it provides attackers with complete control over the affected web server through remote code execution capabilities. An attacker can inject malicious PHP code into user profiles and then access this code through the vulnerable lang parameter in index.php, effectively turning the webmail application into a backdoor for persistent access to the underlying system. This vulnerability directly maps to CWE-22 (Improper Limitation of a Pathname to a Restricted Directory) and CWE-77 (Improper Neutralization of Special Elements used in a Command) categories, establishing it as a fundamental flaw in input validation and file access control mechanisms. The attack chain typically involves initial exploitation through directory traversal, followed by code injection into user profiles, and finally execution through the vulnerable parameter handling.
The threat landscape for this vulnerability aligns with ATT&CK techniques including T1190 (Exploit Public-Facing Application) and T1059.007 (Command and Scripting Interpreter: PHP) where attackers leverage web application flaws to establish persistent access and execute malicious code. Organizations running NOCC Webmail 1.0 are particularly vulnerable as this represents a classic example of insecure file handling in web applications. The vulnerability's exploitation requires minimal privileges and can be automated through existing penetration testing frameworks, making it attractive to both automated attacks and targeted intrusions. System administrators should implement immediate mitigations including input validation, proper parameter sanitization, and disabling unnecessary file inclusion features while also considering the broader implications of similar vulnerabilities in other web applications that may share similar architectural patterns.
The remediation strategy for this vulnerability requires comprehensive application-level fixes including strict input validation for all user-supplied parameters, implementation of proper file access controls, and removal of dangerous file inclusion patterns. Organizations should also implement web application firewalls to detect and block directory traversal attempts, conduct thorough security code reviews to identify similar vulnerabilities in other applications, and establish proper input sanitization routines that prevent null byte injection attacks. Additionally, the application should be configured to disable automatic language and theme switching when default settings are not properly enforced, ensuring that user input cannot override system security controls. This vulnerability serves as a critical reminder of the importance of proper input validation and the potential consequences of inadequate security controls in web applications.