Wordtrans-web Remote Command Execution Vulnerability

Wordtrans-web Remote Command Execution Vulnerability
Scanit R&D; Labs Security Advisory
http://www.scanit.net/rd/advisories/
Jun 30, 2008

Filename:  	SCANIT-2008-002.txt
SCANIT ID: 	SCANIT-2008-002
Published: 	June 30th, 2008


I. Summary

Wordtrans is a free front-end graphical application that allows you to look for
words in several dictionaries. It can also translate the word that the user
selects with his mouse.

The latest Wordtrans version could allow a remote attacker to execute arbitrary
code in the server, caused by an input validation error in the wordtrans-web
package, which is a PHP-based Web interface for Wordtrans.

II. Affected Products

This vulnerability affects the wordtrans 1.1pre15 and probably previous
versions.

III. Details

By Sending a GET request with the variable "command" set to 'show_desc', the
variable "link_options" receives one argument from the user, passed via the
"advanced" variable using the GET method. Then, the variable "link_options" is
concatenated with the variable "exec_wordtrans". Since "exec_wordtrans" is
passed to the function "passthru" without checking for special characters, an
attacker can send shell characters like | or ; to execute commands in the
machine with the privileges of the Web server process at the time the URL is
submitted. This is part of vulnerable script from wordtrans 1.1pre15:

...
$exec_wordtrans = $wordtrans . "-d \"$dict\" ";

switch ($_GET['command']) {
	case "show_desc":
		$exec_wordtrans .= "--desc ";
		$link_options = "--html-link-options \"?lang=$lang_case&advanced=".$_GET['advanced']."&\" ";
		$exec_wordtrans .= $link_options;

		passthru($exec_wordtrans);
		break;
...

To exploit this vulnerability, the "Magic Quotes" option needs to be unset.
But since this option was removed from PHP since version 6.0.0, this is a
critical vulnerability.

IV. Solution

No vendor response.

V. Timeline

March 1st, 2008 - Vulnerability discovery
March 24th, 2008 - First contact attempt
June 30th, 2008 - Advisory release

VI. Credits

This vulnerability was discovered by Scanit's researchers Filipe Balestra
 and Rodrigo Rubira Branco (BSDaemon) 
.

VII. Contact

Scanit's R&D; Labs represent Scanit's efforts in security research activities.
By keeping track of the newest deffensive and offensive technologies, Scanit's
researchers are able to contribute with unpublished works made in-house. This
way, by driving the state-of-the-art in computer security, Scanit honors its
commitment to stay in the front line of scientific evolution.

Reach us at research@scanit.net
Visit http://www.scanit.net

VIII. Disclaimer

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shall the authors be held liable for any direct, indirect, or consequential 
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