CVE-2026-14946 in FDS
Summary
by MITRE • 08/20/2026
A high privileged remote attacker can upload a .php file and then request it directly from /uploads/<filename>.php to achieve arbitrary code execution due to improper file type validation which could result in full system compromise.
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Analysis
by VulDB Data Team • 08/20/2026
The vulnerability described represents a critical server-side security failure rooted in inadequate input validation mechanisms, specifically concerning file uploads. This flaw allows an attacker with high privileges on the remote system to bypass intended access controls and execute arbitrary code by uploading a malicious PHP script. The core technical issue lies in the application's handling of uploaded files, where the backend logic fails to strictly enforce allowed file extensions or validate the content type against expected formats. Instead of relying solely on client-side checks which are easily circumvented, secure implementations must perform rigorous server-side validation including MIME type verification and extension whitelisting. The absence of these controls creates a direct path for remote code execution, as the web server is configured to interpret files with the .php extension as executable scripts rather than static data.
From an operational perspective, this vulnerability poses an extreme risk to system integrity and confidentiality. Once the attacker successfully uploads the malicious PHP file to the designated upload directory, they can trigger its execution by sending a direct HTTP request to the path /uploads/<filename>.php. Because the web server processes this request as code, it runs with the same privileges as the web service process itself. This typically grants the attacker full control over the underlying operating system, enabling them to read sensitive configuration files, exfiltrate database credentials, install backdoors, or pivot further into the internal network. The severity is compounded by the requirement for high privilege access on the remote side, suggesting that this may be an abuse of legitimate administrative functions rather than a direct exploitation from unauthenticated users, yet it still results in complete system compromise if those privileges are obtained through credential theft or other means.
This vulnerability aligns closely with Common Weakness Enumeration identifier CWE-434, which describes the unrestricted upload of files with dangerous types. It also maps to MITRE ATT&CK technique T1505.003, known as Web Shell: Server-Side Script, where attackers deploy scripts on a web server to maintain persistent access and execute commands remotely. The exploitation chain involves two distinct phases: first, the injection of the malicious payload via the upload interface due to validation failures, and second, the remote invocation of that payload through direct URL manipulation. This dual-phase approach highlights the importance of defense-in-depth strategies where multiple layers of security controls are required to prevent such attacks from succeeding even if one layer fails.
Mitigation efforts must focus on implementing robust server-side file upload restrictions. Developers should enforce strict whitelisting for allowed file extensions, ensuring that only expected types like images or documents can be uploaded, while explicitly blocking executable formats such as .php, .jsp, and .asp. Additionally, the storage location for uploaded files should be configured to prevent execution; this can be achieved by placing upload directories outside the web root or configuring the web server software to disable script execution within those specific folders using directives like deny execute permissions in Apache or Nginx configuration files. Implementing content validation that inspects the actual file header rather than just relying on extensions is also critical, as extension spoofing is a common evasion technique. Furthermore, applying principle of least privilege to the web service account ensures that even if an upload succeeds and execution occurs, the potential damage is contained within limited system boundaries. Regular security audits and static code analysis tools can help identify such validation gaps before deployment, reducing the attack surface for high-privilege abuse scenarios.