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e107 <= 0.7.11 Arbitrary Variable Overwriting



e107 <= 0.7.11 Arbitrary Variable Overwriting
e107 <= 0.7.11 Arbitrary Variable Overwriting



##########################################################
# GulfTech Security Research              August 07, 2008
##########################################################
# Vendor : Steve Dunstan
# URL : http://www.e107.org/ 
# Version : e107 <= 0.7.11
# Risk : Arbitrary Variable Overwriting
##########################################################


Description:
e107 is a popular full featured content management system written
in php. Unfortunately e107 suffers from an arbitrary variable
overwriting issue within it's download.php file that allows a number
of possible attacks to happen including, but possibly not limited to,
arbitrary php code execution and SQL Injection. No authentication
is required to exploit the issue and it can be exploited regardless
of php magic quotes settings. All users are encouraged to upgrade
their e107 installations as soon as possible.


Arbitrary Variable Overwriting:
There is an arbitrary variable overwrite issue in download.php that
is the result of unsafe usage of the php extract() function. Let's
have a look at the code located in download.php @ lines 85-86

case 'list' :	// Category-based listing
if (isset($_POST['view'])) extract($_POST);

As we see from the above code it is very much possible to overwrite
any variables declared up to this point, but what is the real risk
here? What attacks are possible because of this issue?

view=1&id=-99') UNION SELECT concat(user_name,char(58), user_password),
2,3,4 FROM e107_user WHERE user_id=1/*

One possible attack could involve an attacker sending a post request
to the downloads category view page (download.php?list.1 for example)
with the above data as the post contents, and as a result the username
and pass hash will be displayed in the page title. This SQL Injection
does require magic quotes to be set to it's default value of off.

view=1&action=maincats&execute=aWQ=&template_load_core=echo%20exec
(base64_decode($_POST[execute]));

In addition to the SQL Injection is an arbitrary php code execution
vulnerability. I found that it is possible to execute arbitrary php
code by sending a post request to the downloads category view page
with the above data as the post contents. The above example will
successfully execute the "id" shell command regardless if php magic
quotes gpc settings. A valid download category must be available
though, but this is trivial since an attacker can use the previously
explained SQL Injection to gain admin credentials and add a download
category. Other attacks may be possible though since a majority of
the important variables within the script are at risk.



Solution:
A fix for the issue mentioned in this advisory can be found in the 
public e107 CVS repository, or accessed directly at the link below.

http://e107.cvs.sourceforge.net/e107/e107_0.7/download.php?r1=1.95&r2=1.96&view=patch&pathrev=MAIN 



Credits:
James Bercegay of the GulfTech Security Research Team



Related Info:
The original advisory can be found at the following location
http://www.gulftech.org/?node=research&article_id=00122-08072008 


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