CVE-2005-4155 in ATutor
Summary
by MITRE
registration.PHP in ATutor 1.5.1 pl2 allows remote attackers to execute arbitrary SQL commands via an e-mail address that ends in a NULL character, which bypasses the PHP regular expression check. NOTE: it is possible that this is actually a bug in PHP code, in which case this should not be treated as a vulnerability in ATutor.
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Analysis
by VulDB Data Team • 03/23/2025
The vulnerability described in CVE-2005-4155 targets ATutor 1.5.1 pl2's registration.php script, representing a critical SQL injection flaw that could enable remote attackers to execute arbitrary database commands. This vulnerability specifically exploits how the application handles email address validation, creating a pathway for malicious input to bypass security controls. The flaw occurs when an email address ends with a NULL character, which allows the input to slip through PHP's regular expression validation checks that are designed to prevent malicious SQL code execution.
The technical implementation of this vulnerability leverages the behavior of PHP's string handling mechanisms, particularly how NULL characters are processed within regular expression matching functions. When a user submits an email address ending in a NULL character, the PHP regular expression functions fail to properly validate the input due to the NULL character's special handling in string comparisons. This creates a bypass condition where the validation logic incorrectly accepts potentially malicious input that would normally be rejected. The vulnerability falls under CWE-89, which specifically addresses SQL injection flaws, and represents a classic case of input validation bypass that can lead to complete database compromise.
The operational impact of this vulnerability is severe, as it provides attackers with the ability to execute arbitrary SQL commands against the ATutor database without authentication. This means unauthorized individuals could potentially extract sensitive user data, modify database contents, or even escalate privileges within the application. The attack vector is particularly concerning because it requires minimal user interaction beyond registration, making it an attractive target for automated exploitation. Attackers could use this vulnerability to gain persistent access to user accounts, modify course materials, or destroy educational content. The vulnerability also aligns with ATT&CK technique T1190, which covers exploiting vulnerabilities in web applications, and T1071.004, covering application layer protocol manipulation.
The remediation approach for this vulnerability requires multiple layers of defense to ensure proper input handling and validation. Organizations should immediately implement proper input sanitization techniques that explicitly handle NULL characters and other special characters in user input. The recommended solution involves strengthening the email validation logic to properly escape or reject NULL characters before they reach the database layer. Additionally, implementing proper parameterized queries and prepared statements would provide defense-in-depth against SQL injection attempts. The vulnerability highlights the importance of robust input validation and the need to consider edge cases in security implementations, particularly when dealing with language-specific behaviors like PHP's string handling. Organizations should also review their entire codebase for similar patterns and implement comprehensive testing procedures that include edge case scenarios involving special characters and null terminators.