PHP-FPM Underflow RCE

This module exploits an underflow vulnerability in versions 7.1.x
below 7.1.33, 7.2.x below 7.2.24 and 7.3.x below 7.3.11 of PHP-FPM on
Nginx. Only servers with certains Nginx + PHP-FPM configurations are
exploitable. This is a port of the original neex's exploit code (see
refs.). First, it detects the correct parameters (Query String Length
and custom header length) needed to trigger code execution. This step
determines if the target is actually vulnerable (Check method). Then,
the exploit sets a series of PHP INI directives to create a file
locally on the target, which enables code execution through a query
string parameter. This is used to execute normal payload stagers.
Finally, this module does some cleanup by killing local PHP-FPM
workers (those are spawned automatically once killed) and removing
the created local file.