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PHP Resource Exhaustion Denial of Service
From: full-disclosure () lists netsys com (Matthew Murphy)
Date: Sat, 20 Jul 2002 20:45:17 -0500

The PHP interpreter is a heavy-duty CGI EXE (or SAPI module, depending on
configuration) that implements an HTML-embedded script language.  A
vulnerability in PHP can be used to cause a denial of service in some cases.

PHP's install process on Apache requires a "/php/" alias to be created, as
it resolves CGI paths to a virtual.  (e.g, /php/php.exe not C:\php\php.exe).

To solve the obvious security vulnerability posed by allowing PHP to run
from the web, the development team added a cgi.force_redirect option that is
enabled by default in Apache.

However, regardless of the force_redirect value, it is still possible to
load the binary without a script path:

(e.g, http://localhost/php/php)

A problem exists in PHP; specifically, it does not terminate when given no
command-line arguments.  A consistent flow of requests like the above will
exhaust all resources for CGI/ASAPI on the server.

Exploit: http://www.murphy.101main.net/php-apache.c

I tried to make sure this would run on Linux/BSD, but no guarantees...
Compiles cleanly on WinMe with MSVC 6.0.



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