CVE-2005-0603 in phpBB
Summary
by MITRE
viewtopic.php in phpBB 2.0.12 and earlier allows remote attackers to obtain sensitive information via a highlight parameter containing invalid regular expression syntax, which reveals the path in a PHP error message.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 07/01/2021
The vulnerability identified as CVE-2005-0603 affects phpBB versions 2.0.12 and earlier, specifically within the viewtopic.php script that handles topic viewing functionality. This issue represents a classic information disclosure vulnerability that occurs when user input is not properly validated or sanitized before being processed by the application's regular expression engine. The flaw manifests when an attacker crafts a malicious highlight parameter containing invalid regular expression syntax, which triggers PHP's error handling mechanism to display sensitive system information including file paths.
The technical exploitation of this vulnerability relies on the application's failure to implement proper input validation and error handling for regular expression processing. When phpBB processes the highlight parameter through its internal regular expression functions, it does not adequately sanitize or validate the input before passing it to PHP's regex engine. This creates an opportunity for attackers to inject malformed regular expression syntax that causes PHP to generate error messages containing the full server path where the application is installed. The vulnerability directly maps to CWE-209, which describes improper handling of error conditions and the exposure of sensitive information through error messages.
The operational impact of this vulnerability extends beyond simple information disclosure as it provides attackers with critical system information that can be leveraged for subsequent attacks. The revealed server paths expose the exact directory structure where phpBB is installed, potentially including database connection details or other sensitive configuration information that might be stored in predictable locations. Attackers can use this information to craft more sophisticated attacks, including directory traversal attempts or exploitation of other vulnerabilities that might exist in the application's file structure. This vulnerability aligns with ATT&CK technique T1083 (File and Directory Discovery) as it enables adversaries to gather system reconnaissance information.
The remediation approach for this vulnerability requires implementing proper input validation and error handling mechanisms within the phpBB application. Developers should sanitize all user-supplied input before processing it through regular expression functions, ensuring that any potentially malicious patterns are neutralized or rejected entirely. Additionally, the application should implement comprehensive error handling that prevents sensitive system information from being exposed to end users. The most effective mitigation involves updating to phpBB version 2.0.13 or later, where this vulnerability has been addressed through improved input validation and error handling procedures. Organizations should also implement proper logging mechanisms to detect and respond to exploitation attempts, while maintaining regular security updates to address similar vulnerabilities in their web applications.