: The default folder where Composer (the package manager for PHP) installs third-party libraries and packages.
If the file exists and the server is vulnerable, the command executes instantly. The server will respond with the name of the system user running the web service (such as www-data ). Once an attacker confirms execution, they typically download a persistent webshell, steal database credentials from .env files, or deploy ransomware. How to Check if Your Server is Vulnerable
The vendor directory should never be publicly accessible.
The eval-stdin.php file contains a simple yet powerful script: index of vendor phpunit phpunit src util php evalstdinphp
The script takes whatever is in the request body and runs it using the eval() function.
Try to request the file without any payload. Even a GET request might reveal the script’s source code. But to confirm RCE, send a benign test:
PHPUnit is the most popular testing framework for PHP. When developers use Composer to manage dependencies, PHPUnit is often installed into the vendor directory. : The default folder where Composer (the package
An attacker sends an HTTP POST request to eval-stdin.php with arbitrary PHP code in the request body. For example:
The attack targets websites that have the vendor directory publicly accessible. This often occurs due to misconfigured web servers (Apache/Nginx) where the web root points to the project root, or where .htaccess rules do not restrict access to internal directories.
The --no-dev flag excludes all packages listed under require-dev (including PHPUnit). Verify your composer.json to ensure PHPUnit is indeed in require-dev , not require . Once an attacker confirms execution, they typically download
When using Composer, always run:
If you intend this for , here’s a sample post you could write:
Why is CVE-2017-9841 such a pervasive problem? The answer lies in how many PHP applications are deployed. Composer, the dependency manager for PHP, downloads all required libraries into a central vendor directory. This includes development-only tools like [9†L9-L10].
PHPUnit is a development tool and should never be deployed to a production environment.
Search engines continue to index these exposed directories. The query index of vendor phpunit phpunit src util php evalstdinphp is used in Google dorks to find live vulnerable sites.