CVE-2025-6905 is a critical SQL Injection vulnerability identified in version 1.0 of the code-projects Car Rental System, specifically affecting the /signup.php endpoint. The vulnerability arises from improper sanitization or validation of the 'fname' parameter, which is used in SQL queries without adequate protection against injection attacks. An attacker can remotely exploit this flaw by crafting malicious input for the 'fname' parameter, allowing unauthorized execution of arbitrary SQL commands on the backend database. This can lead to unauthorized data access, data modification, or even complete compromise of the database server. The vulnerability does not require authentication or user interaction, increasing its risk profile. Although the CVSS v4.0 base score is 6.9 (medium severity), the exploitability is high due to network accessibility and lack of required privileges. The vulnerability impacts confidentiality, integrity, and availability of the system's data, as attackers could extract sensitive customer information, alter records, or disrupt service availability. No official patches or mitigations have been published yet, and no known exploits are reported in the wild, but public disclosure of the exploit code increases the likelihood of active exploitation attempts.

For European organizations using the code-projects Car Rental System 1.0, this vulnerability poses significant risks. Car rental companies often handle sensitive personal data such as customer names, contact details, payment information, and driving license data, which are protected under GDPR regulations. Exploitation could lead to data breaches with severe legal and financial consequences, including fines and reputational damage. Additionally, attackers could manipulate booking records or disrupt rental operations, impacting business continuity. The remote, unauthenticated nature of the vulnerability means attackers can exploit it without insider access, increasing the threat surface. Organizations relying on this software must consider the potential for cross-border data exposure and the need for rapid incident response to comply with European data protection laws.

Given the absence of official patches, European organizations should immediately implement compensating controls. These include deploying Web Application Firewalls (WAFs) with custom rules to detect and block SQL injection patterns targeting the 'fname' parameter on /signup.php. Input validation and sanitization should be enforced at the application layer, ideally by updating or rewriting the vulnerable component to use parameterized queries or prepared statements. Network segmentation can limit database exposure, and monitoring database logs for suspicious queries can help detect exploitation attempts early. Organizations should also conduct thorough code reviews and penetration testing to identify similar injection points. If feasible, migrating to a newer, patched version of the software or alternative solutions is recommended. Finally, organizations must prepare incident response plans aligned with GDPR breach notification requirements.