CVE-2001-1471 in phpBB
Summary
by MITRE
prefs.php in phpBB 1.4.0 and earlier allows remote authenticated users to execute arbitrary PHP code via an invalid language value, which prevents the variables (1) $l_statsblock in prefs.php or (2) $l_privnotify in auth.php from being properly initialized, which can be modified by the user and later used in an eval statement.
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Analysis
by VulDB Data Team • 09/25/2025
This vulnerability exists in phpBB version 1.4.0 and earlier where the prefs.php script contains a critical security flaw that allows authenticated remote attackers to execute arbitrary PHP code. The issue stems from improper variable initialization in the language selection mechanism, specifically affecting the $l_statsblock variable in prefs.php and the $l_privnotify variable in auth.php. When users provide invalid language values, the system fails to properly initialize these variables, creating a dangerous condition where user-supplied input can be manipulated and subsequently processed through eval statements.
The technical exploitation occurs through a classic variable injection vulnerability where the lack of proper input validation and sanitization allows attackers to manipulate the language parameter to bypass normal initialization procedures. This flaw operates at the intersection of improper input validation and code execution, with the vulnerability being classified under CWE-94 as "Improper Control of Generation of Code ('Code Injection')" and CWE-20 as "Improper Input Validation." The vulnerability is particularly dangerous because it requires only authenticated access, meaning any registered user can potentially exploit it to execute arbitrary code on the server.
The operational impact of this vulnerability is severe as it provides attackers with the ability to execute arbitrary PHP code with the privileges of the web server, potentially leading to complete system compromise. Attackers can leverage this flaw to gain unauthorized access to sensitive data, install backdoors, modify database contents, or even escalate privileges to system level access. The vulnerability is particularly concerning in environments where phpBB is used for forums with significant user bases, as the authenticated nature of the exploit makes it more difficult to detect and prevent.
Mitigation strategies should focus on immediate patching of the phpBB application to version 1.4.1 or later where this vulnerability has been addressed through proper input validation and variable initialization. Additionally, administrators should implement proper input sanitization measures, including validating and filtering all user-supplied language parameters before they are processed. The principle of least privilege should be enforced by ensuring that web server processes run with minimal required permissions. Network-level protections such as web application firewalls can provide additional detection capabilities for suspicious language parameter values, while regular security monitoring should be implemented to identify potential exploitation attempts. Organizations should also consider implementing proper access controls and audit logging to track user activities that might indicate exploitation attempts.