CVE-2009-0543 in ProFTPD
Summary
by MITRE
ProFTPD Server 1.3.1, with NLS support enabled, allows remote attackers to bypass SQL injection protection mechanisms via invalid, encoded multibyte characters, which are not properly handled in (1) mod_sql_mysql and (2) mod_sql_postgres.
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Analysis
by VulDB Data Team • 01/13/2025
The vulnerability identified as CVE-2009-0543 affects ProFTPD Server version 1.3.1 when NLS support is enabled, creating a critical security flaw that undermines SQL injection protection mechanisms. This vulnerability specifically targets the mod_sql_mysql and mod_sql_postgres modules, which are responsible for database connectivity and authentication within the FTP server framework. The flaw arises from improper handling of invalid, encoded multibyte characters that are not correctly sanitized or validated during the processing of user input. When these malformed characters are processed through the SQL connection modules, they can bypass the intended security controls designed to prevent malicious SQL code execution, potentially allowing unauthorized access to backend databases and sensitive information.
The technical implementation of this vulnerability stems from the server's inadequate character encoding validation mechanisms within the NLS (Native Language Support) subsystem. When NLS support is enabled, ProFTPD processes multibyte character sequences to support international character sets, but fails to properly validate or sanitize these sequences before they are passed to SQL query construction functions. This creates a pathway where attackers can craft malicious input containing specially encoded multibyte characters that are interpreted differently by the database driver than by the application logic, effectively neutralizing SQL injection prevention measures. The vulnerability specifically impacts the mod_sql_mysql and mod_sql_postgres modules because these components handle database authentication and query execution, making them prime targets for exploitation. The flaw operates at the intersection of character set handling and database security, where the application's expectation of properly formatted input conflicts with the actual processing of malformed multibyte sequences.
The operational impact of this vulnerability extends beyond simple SQL injection attacks, potentially enabling full database compromise and unauthorized access to sensitive user data. Attackers can exploit this weakness to execute arbitrary SQL commands against the backend database, potentially gaining read access to user credentials, personal information, or other sensitive data stored within the system. The vulnerability's remote nature means that attackers do not require local system access to exploit the flaw, making it particularly dangerous for publicly accessible FTP servers. Organizations running ProFTPD with NLS support enabled and database connectivity features are at risk of unauthorized data access, potential data breaches, and possible system compromise. The implications are particularly severe for environments where FTP servers are used for database authentication or where sensitive information is stored in connected databases, as the vulnerability can be leveraged to bypass authentication mechanisms and access critical data repositories.
Mitigation strategies for CVE-2009-0543 should focus on immediate patching of the ProFTPD server to address the character encoding validation issues within the affected modules. System administrators should disable NLS support if it is not essential for their operations, as this removes the attack vector entirely. Additionally, implementing proper input validation at multiple layers of the application stack can help detect and prevent malformed character sequences from reaching the database connection modules. Organizations should also consider implementing database-level security controls such as prepared statements and parameterized queries to minimize the impact of any potential exploitation attempts. Network segmentation and firewall rules should be configured to limit access to FTP services to trusted networks only, reducing the attack surface. This vulnerability aligns with CWE-119, which addresses improper restriction of operations within a limited access scope, and maps to ATT&CK technique T1190, which covers exploit public-facing application, highlighting the importance of proper input validation and secure coding practices in preventing such attacks. Regular security assessments and vulnerability scanning should be conducted to identify similar character encoding issues in other applications and systems that may be vulnerable to analogous attacks.