CVE-2026-22521 is a Remote File Inclusion (RFI) vulnerability identified in the G5Theme Handmade Framework, a PHP-based web framework used in content management and website development. The root cause is improper control of filenames used in PHP include or require statements, classified under CWE-98. This flaw allows an attacker to manipulate the filename parameter to include remote malicious PHP files, which the server then executes. This can lead to full remote code execution, enabling attackers to compromise the confidentiality, integrity, and availability of the affected web server and its hosted applications. The vulnerability affects Handmade Framework versions up to 3.9, with no specific version exclusions noted. The CVSS v3.1 base score is 7.5, indicating a high severity level. The vector metrics specify network attack vector (AV:N), high attack complexity (AC:H), low privileges required (PR:L), no user interaction (UI:N), unchanged scope (S:U), and high impact on confidentiality, integrity, and availability (C:H/I:H/A:H). Although no exploits have been reported in the wild yet, the vulnerability presents a significant risk due to the potential for remote code execution. The lack of available patches at the time of publication necessitates immediate mitigation efforts by administrators. The vulnerability is particularly dangerous because PHP include/require statements are common in web applications, and improper sanitization of input parameters can easily be exploited if not properly controlled. Attackers can leverage this flaw to upload backdoors, steal sensitive data, or disrupt services.

For European organizations, the impact of CVE-2026-22521 can be severe. Many European businesses rely on PHP-based CMS and frameworks for their web presence, including e-commerce, government portals, and corporate websites. Successful exploitation could lead to unauthorized access to sensitive customer data, intellectual property theft, defacement of websites, and disruption of critical online services. This can result in financial losses, reputational damage, and regulatory penalties under GDPR due to data breaches. The high confidentiality, integrity, and availability impact means attackers could manipulate or destroy data, implant persistent malware, or use compromised servers as pivot points for further attacks. Organizations with limited patch management capabilities or those using outdated versions of the Handmade Framework are particularly vulnerable. The absence of known exploits in the wild provides a window for proactive defense, but also means attackers may develop exploits soon, increasing urgency for mitigation.

1. Monitor official G5Theme channels for patches or updates addressing CVE-2026-22521 and apply them immediately once available. 2. Implement strict input validation and sanitization on all parameters that influence file inclusion paths to prevent injection of remote URLs or unauthorized file paths. 3. Configure PHP settings to disable allow_url_include and allow_url_fopen directives to prevent remote file inclusion. 4. Use web application firewalls (WAFs) with rules targeting RFI attack patterns to detect and block malicious requests. 5. Restrict file inclusion to a whitelist of trusted directories using PHP’s open_basedir directive. 6. Conduct thorough code audits of customizations or plugins that interact with the Handmade Framework to identify and remediate unsafe include/require usage. 7. Employ network segmentation and least privilege principles to limit the impact of a potential compromise. 8. Regularly scan web applications with vulnerability scanners that detect RFI vulnerabilities. 9. Maintain comprehensive logging and monitoring to detect anomalous file inclusion attempts or unexpected remote connections. 10. Educate development and security teams about secure coding practices related to file inclusion in PHP.