CVE-2025-70457 is a critical Remote Code Execution (RCE) vulnerability identified in the Sourcecodester Modern Image Gallery App version 1.0, specifically within the gallery/upload.php file handling image uploads. The vulnerability arises because the application fails to properly validate the contents of uploaded files, relying instead on user-supplied MIME types and preserving the original file extensions without verification. This flaw allows an unauthenticated attacker to craft a malicious file containing PHP code, spoof its MIME type as an image, and upload it to the server. Since the application saves the file with the attacker-controlled extension and does not sanitize or restrict executable code, the attacker can then execute arbitrary PHP code on the server. This leads to full system compromise, including the ability to read, modify, or delete data, install backdoors, or pivot within the network. The vulnerability is classified under CWE-434 (Unrestricted Upload of File with Dangerous Type) and has a CVSS v3.1 base score of 9.8, reflecting its critical severity. The attack vector is network-based, requires no authentication or user interaction, and affects the confidentiality, integrity, and availability of the affected system. Although no known exploits have been reported in the wild yet, the straightforward exploitation method and severe impact make it a significant threat. No official patches have been released at the time of publication, increasing the urgency for organizations to implement mitigations.

For European organizations, this vulnerability poses a significant risk, especially for those deploying the Sourcecodester Modern Image Gallery App or similar vulnerable web applications. Successful exploitation can lead to complete system takeover, data breaches, defacement of websites, disruption of services, and potential lateral movement within corporate networks. Organizations handling sensitive personal data, intellectual property, or critical infrastructure could suffer severe confidentiality and integrity losses, as well as operational downtime. The lack of authentication and user interaction requirements means attackers can remotely exploit this vulnerability at scale, increasing the likelihood of widespread attacks. Additionally, compromised servers could be used as launchpads for further attacks, including ransomware or supply chain compromises, impacting broader European digital ecosystems. The reputational damage and regulatory consequences under GDPR for data breaches further amplify the impact on affected entities.

To mitigate this vulnerability, organizations should immediately disable file upload functionality in the affected application if not essential. If uploads are required, implement strict server-side validation of uploaded files, including verifying file contents using magic numbers or file signature checks rather than relying on MIME types or extensions. Enforce a whitelist of allowed file types and rename uploaded files to safe extensions that cannot be executed by the server (e.g., .txt or .dat). Configure the web server to prevent execution of uploaded files by isolating upload directories outside the web root or disabling script execution permissions in those directories. Employ web application firewalls (WAFs) with custom rules to detect and block suspicious upload attempts. Monitor logs for unusual upload activity or access patterns. Regularly update and patch the application once a vendor fix is available. Conduct security audits and penetration testing focused on file upload mechanisms. Educate developers on secure coding practices related to file handling to prevent similar vulnerabilities in future deployments.