CVE-2009-4733 in SimpleLoginSys
Summary
by MITRE
SQL injection vulnerability in checkuser.php in SimpleLoginSys 0.5, when magic_quotes_gpc is disabled, allows remote attackers to execute arbitrary SQL commands via the username parameter. NOTE: some of these details are obtained from third party information.
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Analysis
by VulDB Data Team • 05/02/2026
The vulnerability identified as CVE-2009-4733 represents a critical sql injection flaw within the SimpleLoginSys 0.5 authentication system. This vulnerability specifically targets the checkuser.php script which processes user authentication requests. The flaw manifests when the php configuration parameter magic_quotes_gpc is disabled, creating an environment where user input is not automatically escaped, thereby exposing the application to malicious sql command injection attacks. The vulnerability is particularly dangerous because it allows remote attackers to execute arbitrary sql commands directly against the backend database without proper authentication or authorization.
The technical exploitation of this vulnerability occurs through the username parameter in the checkuser.php script. When magic_quotes_gpc is disabled, the application fails to properly sanitize user input before incorporating it into sql queries. This creates a direct pathway for attackers to inject malicious sql payloads that can manipulate database operations, potentially leading to data extraction, modification, or deletion. The vulnerability aligns with CWE-89 which categorizes sql injection as a fundamental weakness in software design where untrusted data is directly included in sql commands without proper validation or escaping mechanisms. The attack vector leverages the principle that when input validation is insufficient, attackers can manipulate the intended flow of sql execution by injecting additional sql syntax into parameter values.
The operational impact of this vulnerability extends beyond simple data theft, as it can enable complete database compromise and potential system infiltration. Attackers can leverage this flaw to extract sensitive user credentials, personal information, and other confidential data stored within the application's database. The vulnerability also provides potential for privilege escalation attacks, where attackers might gain elevated access rights within the system. This represents a significant concern for organizations using SimpleLoginSys 0.5, as the vulnerability can be exploited remotely without requiring any prior authentication or system access. The attack surface is particularly broad since the vulnerability affects the core authentication functionality, potentially compromising the entire user management system.
Mitigation strategies for CVE-2009-4733 should focus on immediate remediation and long-term security hardening. The most direct solution involves implementing proper input validation and sanitization mechanisms within the checkuser.php script to prevent malicious sql injection attempts. This includes using parameterized queries or prepared statements which separate sql command structure from data values, thereby preventing the execution of injected sql code. Organizations should also consider enabling magic_quotes_gpc as a temporary workaround, though this approach is not recommended for modern applications due to its limitations and potential conflicts with newer php versions. Additionally, implementing web application firewalls and input filtering mechanisms can provide additional layers of protection against similar vulnerabilities. The remediation efforts should align with established security frameworks such as those recommended by the center for cybersecurity best practices and should incorporate regular security testing including sql injection vulnerability assessments to prevent similar issues from emerging in the future.