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22 mar 2024 · By understanding the full potential of file upload vulnerabilities we can achieve high severity impact that even if it’s not direct RCE with a webshell, it’s still can harm a server in other...
We'll show you how to bypass common defense mechanisms in order to upload a web shell, enabling you to take full control of a vulnerable web server. Given how common file upload functions are, knowing how to test them properly is essential knowledge.
Test Upload of Malicious Files. Many application’s business processes allow users to upload data to them. Although input validation is widely understood for text-based input fields, it is more complicated to implement when files are accepted.
The Unrestricted File Upload vulnerability article describes how attackers may attempt to bypass such a check. Content-Type Validation ¶ The Content-Type for uploaded files is provided by the user, and as such cannot be trusted, as it is trivial to spoof.
Although it should not be relied upon for security, it provides a quick check to prevent users from unintentionally uploading files with the incorrect type. Other than defining the extension of the uploaded file, its MIME-type can be checked for a quick protection against simple file upload attacks.
The unrestricred file upload vulnerability exists within applications where file upload functions do not have the correct controls in place to ensure user uploaded files are restricted, validated or sanitised. This document outlines the testing process for file upload functions while performing a penetration test.
25 maj 2021 · Exiftool versions 7.44 through 12.23 inclusive are vulnerable to a local command execution vulnerability when processing djvu files. Knowing this, if a web application is accepting uploaded files, which are then passed to exiftool, can, in turn, lead to RCE (see reference for an example).
