CVE-2009-0542 in ProFTPD
Summary
by MITRE
SQL injection vulnerability in ProFTPD Server 1.3.1 through 1.3.2rc2 allows remote attackers to execute arbitrary SQL commands via a "%" (percent) character in the username, which introduces a " " (single quote) character during variable substitution by mod_sql.
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Analysis
by VulDB Data Team • 11/23/2024
The vulnerability identified as CVE-2009-0542 represents a critical sql injection flaw within the ProFTPD server software affecting versions 1.3.1 through 1.3.2rc2. This weakness stems from inadequate input validation mechanisms within the mod_sql module which handles database connections for ftp authentication. The vulnerability specifically manifests when a remote attacker submits a username containing a percent character followed by certain sequences that trigger variable substitution processes within the sql query construction. During this substitution process, the percent character is interpreted as a format specifier which inadvertently introduces single quote characters into the sql query string, effectively breaking out of the intended sql parameter context.
The technical exploitation of this vulnerability occurs through careful crafting of username inputs that leverage the variable substitution mechanism within the mod_sql module. When the ftp server processes authentication requests, it constructs sql queries to validate user credentials against backend databases. The presence of the percent character in the username triggers the substitution logic which converts the percent symbol into a single quote during query formation, thereby allowing attackers to inject malicious sql commands directly into the authentication flow. This creates a scenario where legitimate sql queries are disrupted and replaced with attacker-controlled sql statements that can execute arbitrary database operations with the privileges of the database user account used by ProFTPD.
The operational impact of this vulnerability extends beyond simple authentication bypasses to encompass full database compromise capabilities. An attacker who successfully exploits this vulnerability can execute arbitrary sql commands against the backend database, potentially gaining access to sensitive user credentials, personal information, and other database content. The remote nature of the attack means that adversaries can exploit this weakness without requiring physical access to the server or prior authentication. This vulnerability directly maps to CWE-89 which categorizes sql injection flaws, and aligns with attack patterns described in the mitre ATT&CK framework under technique T1190 for exploit public-facing application, specifically targeting database applications through authentication mechanisms.
Mitigation strategies for this vulnerability require immediate implementation of software updates to versions 1.3.2rc3 and later where the input validation issues have been addressed. System administrators should also implement proper input sanitization measures including character filtering and parameterized queries to prevent similar vulnerabilities from manifesting in other applications. Network segmentation and access controls should be enhanced to limit exposure of ftp services to trusted networks only, while monitoring systems should be configured to detect unusual authentication patterns that might indicate exploitation attempts. Additionally, database access privileges should be strictly limited to the minimum required for ProFTPD operations, and regular security audits should verify that all authentication mechanisms properly validate and sanitize user inputs before processing. The vulnerability demonstrates the critical importance of proper input validation in database-connected applications and serves as a reminder of the potential for authentication bypasses to escalate into full system compromises when proper security measures are not implemented.