CVE-2025-70457 is a critical remote code execution vulnerability identified in the Sourcecodester Modern Image Gallery App version 1.0. The flaw exists in the gallery/upload.php script, which handles file uploads but fails to properly validate the actual content of uploaded files. Instead, it relies on the MIME type provided by the user and preserves the user-supplied file extension when saving files. This design flaw allows an unauthenticated attacker to upload malicious PHP scripts disguised as image files by spoofing the MIME type. Once uploaded, the attacker can execute arbitrary code on the server, leading to full system compromise. The vulnerability does not require any authentication or user interaction, making it highly exploitable. The absence of a CVSS score indicates that this is a newly published vulnerability with no official severity rating yet, but the technical details clearly indicate a severe risk. No patches or known exploits are currently reported, but the vulnerability's nature suggests it could be weaponized quickly. The vulnerability highlights the critical importance of validating file contents on the server side, not relying solely on MIME types or file extensions, and implementing strict controls on file uploads to prevent execution of unauthorized code.

For European organizations, the impact of this vulnerability can be severe. Exploitation could lead to full system compromise, allowing attackers to execute arbitrary code, access sensitive data, pivot within networks, and deploy further malware or ransomware. Organizations running the affected application on public-facing web servers are particularly vulnerable, as the flaw allows unauthenticated remote exploitation. This can disrupt business operations, lead to data breaches, and damage organizational reputation. The vulnerability also increases the risk of lateral movement within networks, potentially affecting critical infrastructure or sensitive government and enterprise systems. Given the ease of exploitation and the potential for complete control over affected systems, the threat is significant for sectors such as finance, healthcare, government, and critical infrastructure in Europe. The lack of authentication and user interaction requirements further exacerbates the risk, making automated exploitation feasible.

To mitigate this vulnerability, organizations should immediately implement strict server-side validation of uploaded files, verifying actual file content rather than relying on MIME types or extensions. Employ allowlists for acceptable file types and reject any files that do not strictly conform to expected image formats. Disable execution permissions on directories used for file uploads to prevent execution of uploaded scripts. Monitor web server logs for suspicious upload attempts and anomalous file executions. If possible, isolate the upload functionality in a sandboxed environment to limit potential damage. Organizations should also track vendor advisories for patches or updates addressing this vulnerability and apply them promptly once available. Additionally, consider implementing web application firewalls (WAFs) with rules to detect and block malicious upload attempts targeting this vulnerability. Regular security audits and penetration testing focusing on file upload mechanisms can help identify similar weaknesses.