This is the most direct fix. Update your project's phpunit/phpunit Composer dependency to version 5.6.3 or 4.8.28 or any later release. Run this command in your project root:
curl -d "<?php system('id'); ?>" https://target.com/vendor/phpunit/phpunit/src/Util/PHP/eval-stdin.php
The vulnerability exists because the eval-stdin.php file allows execution of arbitrary PHP code via the HTTP POST body.
POST /vendor/phpunit/phpunit/src/Util/PHP/eval-stdin.php HTTP/1.1 vendor phpunit phpunit src util php eval-stdin.php cve
Ensure your web server configuration denies access to the vendor folder entirely. In Nginx, this can be done by adding a location block to deny access to ^/vendor/.* .
In addition to updating PHPUnit, there are several best practices you can follow to minimize the risk of exploitation:
Successful exploitation allows attackers to perform highly damaging actions, such as: This is the most direct fix
Prevent direct access to any script inside vendor/ :
Here are the details regarding this issue:
This file is part of PHPUnit's internal structure and was never intended to be a public-facing web script. Its function is to receive code over php://stdin and execute it with eval() —a necessity for PHPUnit's own internal processes, but catastrophic if done on a web server. POST /vendor/phpunit/phpunit/src/Util/PHP/eval-stdin
<?php system('id'); ?>
By sending a standard HTTP POST request to this file, an unauthenticated attacker could include arbitrary PHP code in the request body. If the payload began with the
: The script lacked identity checks, login gates, or access rules. Anyone who could reach the file could run code through it.
Nearly a decade after its public disclosure, data from threat intelligence groups like the VulnCheck Canary Network shows that this single file continues to suffer tens of thousands of automated exploitation attempts daily. This article provides a comprehensive deep dive into how CVE-2017-9841 works, why it remains a favorite target for global botnets, and how to definitively secure your systems against it. Technical Overview of CVE-2017-9841 The Root Cause: Unauthenticated Code Injection