CVE-2006-2406 in Unclassified NewsBoard
Summary
by MITRE
Directory traversal vulnerability in bb_lib/abbc.css.php in Unclassified NewsBoard (UNB) 1.5.3-d and possibly earlier versions, when register_globals is enabled, allows remote attackers to include arbitrary files via .. (dot dot) sequences and a trailing null byte (%00) in the design_path parameter. NOTE: this is closely related, but a different vulnerability than the ABBC[Config][smileset] parameter.
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Analysis
by VulDB Data Team • 08/21/2017
The vulnerability described in CVE-2006-2406 represents a critical directory traversal flaw within the Unclassified NewsBoard (UNB) 1.5.3-d software and potentially earlier versions. This security weakness specifically affects the bb_lib/abbc.css.php component and manifests when the PHP configuration parameter register_globals is enabled. The vulnerability enables remote attackers to execute arbitrary file inclusion attacks by manipulating the design_path parameter through carefully crafted dot-dot-slash sequences combined with a trailing null byte encoding. This particular exploit technique leverages the dangerous combination of directory traversal and null byte injection to bypass security controls that might otherwise prevent unauthorized file access.
The technical implementation of this vulnerability stems from improper input validation within the abbc.css.php script. When register_globals is enabled, the application directly incorporates user-supplied input from the design_path parameter into file inclusion operations without adequate sanitization or validation. Attackers can construct malicious URLs that include .. sequences to navigate up directory trees and append %00 null bytes to terminate strings, effectively bypassing path restrictions. This flaw operates under CWE-22, which categorizes directory traversal vulnerabilities, and demonstrates how insecure input handling can lead to arbitrary code execution or information disclosure. The vulnerability is particularly dangerous because it combines multiple attack vectors into a single exploit payload that can be executed remotely without authentication.
The operational impact of CVE-2006-2406 extends beyond simple file access violations to potentially enable complete system compromise. An attacker who successfully exploits this vulnerability can include arbitrary files from the server filesystem, potentially leading to remote code execution, data theft, or system takeover. The attack surface is significant because the vulnerability affects versions of UNB that may have been widely deployed in web environments where register_globals remains enabled, which was common in older PHP configurations. This flaw directly relates to ATT&CK technique T1505.003, which covers server-side include attacks, and demonstrates how legacy PHP configurations can create persistent security risks. The vulnerability also connects to T1083, which covers file and directory discovery, as attackers can use this weakness to explore the server filesystem structure.
Mitigation strategies for this vulnerability must address both the immediate software flaw and underlying configuration issues. The primary recommendation involves disabling the register_globals PHP directive in all affected installations, as this configuration parameter fundamentally enables the attack vector. Additionally, administrators should upgrade to patched versions of UNB if available, or implement proper input validation and sanitization within the affected script. The solution should include implementing proper parameter validation that rejects or escapes directory traversal sequences, and employing a whitelist approach for acceptable design_path values. Security measures should also include restricting file inclusion operations to predefined directories and implementing proper access controls to prevent unauthorized file access. Organizations should conduct comprehensive audits of their PHP configurations to ensure register_globals is disabled and implement input validation at multiple layers to prevent similar vulnerabilities from being exploited in other applications.