CVE-2006-2219 in phpBB
Summary
by MITRE
phpBB 2.0.20 does not verify user-specified input variable types before being passed to type-dependent functions, which allows remote attackers to obtain sensitive information, as demonstrated by the (1) mode parameter to memberlist.php and the (2) highlight parameter to viewtopic.php that are used as an argument to the htmlspecialchars or urlencode functions, which displays the installation path in the resulting error message.
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Analysis
by VulDB Data Team • 08/19/2018
The vulnerability identified as CVE-2006-2219 affects phpBB version 2.0.20 and represents a critical input validation flaw that enables remote attackers to extract sensitive system information through improper handling of user-supplied parameters. This issue stems from the application's failure to validate data types before processing user input, creating a pathway for information disclosure attacks that can reveal critical system details including installation paths.
The technical implementation of this vulnerability occurs within two specific script files where user parameters are processed without adequate type checking. The mode parameter in memberlist.php and the highlight parameter in viewtopic.php are particularly susceptible because they are directly passed to functions like htmlspecialchars and urlencode without proper validation of their data types. When these functions encounter unexpected input types, they generate error messages that inadvertently expose the server's file system structure including the complete installation path where phpBB is deployed.
This vulnerability directly maps to CWE-20, which describes improper input validation, and specifically relates to CWE-200, which covers information exposure. The operational impact of this flaw extends beyond simple information disclosure as it provides attackers with critical system topology information that can be leveraged for subsequent exploitation attempts. The exposure of installation paths enables attackers to understand the server's directory structure, potentially revealing other vulnerabilities or aiding in the development of more sophisticated attack vectors.
The attack methodology involves sending maliciously crafted parameters to the vulnerable phpBB scripts, which then process these inputs through the affected functions and produce error messages containing the installation path. This represents a classic example of how improper input handling can lead to unintended information disclosure, with the attacker exploiting the application's error reporting mechanisms to gain system knowledge.
Security professionals should note that this vulnerability aligns with ATT&CK technique T1083, which involves discovering system information through reconnaissance activities. The flaw demonstrates how applications that fail to validate input parameters can inadvertently become information repositories for attackers. Organizations should implement comprehensive input validation measures that ensure all user-supplied parameters conform to expected data types before processing, particularly when these parameters are passed to system functions that may generate error messages containing sensitive information.
The recommended mitigations include implementing strict type checking for all user-supplied parameters, sanitizing input data before processing, and configuring error handling to prevent sensitive information exposure in error messages. Additionally, upgrading to patched versions of phpBB 2.0.20 or newer releases that address this vulnerability is essential. Organizations should also consider implementing web application firewalls and input validation rules to prevent exploitation attempts, while conducting regular security assessments to identify similar input validation vulnerabilities in other applications.