CVE-2026-37637: Alexantr Filemanager Remote Code Execution Vulnerability Analysis

CVE-2026-37637 Vulnerability Overview Vulnerability Type: Remote Code Execution (RCE) Affected Product: Alexantr filemanager v1.0 Affected Component: Attack Vector: Remote Authentication Requirement: Depends on deployment/configuration Root Cause: Unrestricted file upload and lack of server-side file validation Impact An attacker can upload a malicious PHP file and execute arbitrary system commands by accessing that file via a browser. Successful exploitation can lead to: - Execution of arbitrary commands on the server - Reading of sensitive files - Modification or deletion of application files - Upload of additional malware or web shells - Further penetration into the hosting environment - Complete control over the affected server Technical Details The application allows users to upload arbitrary files without properly validating file extensions, MIME types, or file contents. Example malicious PHP file: Once uploaded to an accessible web directory, the attacker can execute commands by accessing the file via a browser and passing the command through the parameter. Example URL: Reproduction Steps 1. Clone the Vulnerable Application 2. Start the PHP Development Server 3. Access the Application - Open the application in a browser: - Depending on deployment or configuration, the application may also be accessible via: 4. Upload Malicious PHP File - Create a file named : - Upload the file using the application's upload feature. 5. Execute Command - After uploading the file, access it directly from the browser: - If the exploitation is successful, the server will execute the command and return the output. - Example output: Proof of Concept (POC) Malicious PHP Payload Example Request Expected Result - The command provided via the parameter is executed on the server. Root Cause The vulnerability is caused by insufficient server-side validation in the file upload functionality. The application fails to properly restrict: - File extensions - MIME types - File contents - Upload targets - Execution permissions within the upload directory Consequently, executable PHP files can be uploaded and executed directly. Recommended Remediation 1. Block Dangerous File Extensions - Prohibit the upload of executable file types, such as: 2. Use a Whitelist - Allow only expected file types, for example: 3. Validate MIME Type and File Content - Do not rely solely on the client-provided header. - File validation should be performed on the server side. 4. Store Uploaded Files Outside the Web Root - Uploaded files should not be directly executable or publicly accessible. 5. Disable PHP Execution in Upload Directories - For Apache, this can be achieved using : - For Nginx, prevent PHP processing in the upload path: 6. Rename Uploaded Files - Use randomly server-generated filenames and remove user-controlled extensions. 7. Apply Appropriate Access Control - Restrict the use of the upload functionality to trusted users only. Detection Administrators can look for suspicious upload PHP files in web-accessible directories. Example indicators: - - - - - files in upload directories Suspicious request patterns may include: - - - - Example log entry: Disclaimer This repository is intended solely for educational and defensive security purposes. The information and proof of concepts are designed to help developers, system administrators, and security professionals understand and fix vulnerabilities. This information must not be used to attack systems without explicit authorization. Unauthorized access to computer systems is illegal. The author is not responsible for any misuse of the information provided in this repository. References https://github.com/alexantr/filemanager https://cve.mitre.org/

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CVE-2026-37637: Alexantr Filemanager Remote Code Execution Vulnerability Analysis

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