![]() Typically, this bypasses basic blacklist filters by adding additional null characters that are then allowed or not processed by the backend. ![]() Null byte injection bypasses application filtering within web applications by adding URL encoded “Null bytes” such as %00. Useful tiny PHP back doors for the above techniques: Once code has been injected into the User Agent header a local file inclusion vulnerability can be leveraged to execute /proc/self/environ and reload the environment variables, executing your reverse shell. If it’s possible to include /proc/self/environ via a local file inclusion vulnerability, then introducing source code via the User Agent header is a possible vector. Have your web applications been asessed recenty? See our web application penetration testing services page for more information. If the file upload function does not allow zip files to be uploaded, attempts can be made to bypass the file upload function (see: OWASP file upload testing document). The above will extract the zip file to shell, if the server does not append.Use the zip wrapper to extract the payload using: php?page=zip://path/to/file.zip%23shell.Upload the compressed shell payload to the server.A typical attack example would look like: zip files server side allowing the upload of a zip file using a vulnerable file function exploitation of the zip filter via an LFI to execute. Image description: An image showing the output from /etc/passwd on a UNIX / Linux system using php://filter PHP ZIP Wrapper LFI The above is an effort to display the contents of the /etc/passwd file on a UNIX / Linux based system.īelow is an example of a successful exploitation of an LFI vulnerability on a web application: Any script that includes a file from a web server is a good candidate for further LFI testing, for example:Ī security consultant would attempt to exploit this vulnerability by manipulating the file location parameter, such as: LFI vulnerabilities are typically easy to identify and exploit. The following is an example of PHP code vulnerable to local file inclusion. This vulnerability exists when a web application includes a file without correctly sanitising the input, allowing and attacker to manipulate the input and inject path traversal characters and include other files from the web server. ![]() Local File Inclusion (LFI) allows an attacker to include files on a server through the web browser. What is a Local File Inclusion (LFI) vulnerability? LFI vulnerabilities are typically discovered during application assessments or bug bounty testing using the techniques contained within this document. The intent of this document is to assist with web app security assessments engagements by consolidating research for LFI testing techniques.
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