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SEC Consult Vulnerability Lab Security Advisory < 20180712-0 >
=======================================================================
              title: Remote Code Execution & Local File Disclosure
            product: Zeta Producer Desktop CMS
 vulnerable version: <=14.2.0
      fixed version: >=14.2.1
         CVE number: CVE-2018-13981, CVE-2018-13980
             impact: critical
           homepage: https://www.zeta-producer.com
              found: 2017-11-25
                 by: P. Morimoto (Office Bangkok)
                     SEC Consult Vulnerability Lab 

                     An integrated part of SEC Consult
                     Europe | Asia | North America

                     https://www.sec-consult.com

=======================================================================

Vendor description:
-------------------
"With Zeta Producer, the website builder and online shop system for Windows, 
you can create and manage your website locally, on your computer. 
Get without expertise in 3 steps to your own homepage: select design, 
paste content, publish website. Finished."

Source: https://www.zeta-producer.com/de/index.html


Business recommendation:
------------------------
The vendor provides a patched version which should be installed immediately.

Users of the product also need to verify that the affected widgets are updated in
the corresponding website project! It could be necessary to rebuild the whole project
or copy the new widgets to the website projects. For further information consult the
vendor.

Furthermore, an in-depth security analysis is highly advised, as the software may be
affected from further security issues.


Vulnerability overview/description:
-----------------------------------
1) Remote Code Execution (CVE-2018-13981)
The email contact functionality of the widget "formmailer" can upload files
to the server but if the user uploads a PHP script with a .php extension 
then the server will rename it to .phps to prevent PHP code execution.

However, the attacker can upload .php5 or .phtml to the server without any 
restriction. These alternative file extensions can be executed as PHP code. 

Furthermore, the server will create a folder to store the files, with a
random name using PHP's "uniqid" function.

Unfortunately, if the server permits directory listing, the attacker
can easily browse to the uploaded PHP script. If no directory listing is 
enabled the attacker can still bruteforce the random name to gain remote 
code execution via the PHP script as well. Testing on a local server it 
took about 20 seconds to brute force the random name. This attack will 
be slower over the Internet but it is still feasible.

Also, if the user runs the Zeta Producer Desktop CMS GUI client locally,
they are also vulnerable because the web server will be running on TCP port 9153.

The root cause is in the widget "formmailer" which is enabled by default.
The following files are affected:
- /assets/php/formmailer/SendEmail.php
- /assets/php/formmailer/functions.php


2) Local File Disclosure (CVE-2018-13980)
If the user enables the widget "filebrowser" on Zeta Producer Desktop CMS an 
unauthenticated attacker can read local files by exploiting path traversal issues. 

The following files are affected:
- /assets/php/filebrowser/filebrowser.main.php


Proof of concept:
-----------------
1) Remote Code Execution (CVE-2018-13981)
The following python script can be used to exploit the chain of vulnerabilities.
[.. code has been removed to prevent misuses ..]

When the script is executed, a PHP script (shell) will be uploaded automatically.
# $ python exploit.py
# [+] injecting webshell to http://target/assets/php/formmailer/SendEmail.php
#
# 5a1a5bc991afe
# 5a1a5bc99453a
# 10812
# [*] Found :  http://target/assets/php/formmailer/upload_5a1a5bc992772/sectest.php5
# uid=33(www-data) gid=33(www-data) groups=33(www-data)


2) Local File Disclosure (CVE-2018-13980)
The parameter "file" in the "filebrowser.main.php" script can be exploited to read
arbitrary files from the OS with the privileges of the web server user.
Any unauthenticated user can exploit this issue!

http://target/assets/php/filebrowser/filebrowser.main.php?file=../../../../../../../../../../etc/passwd&do=download
http://target/assets/php/filebrowser/filebrowser.main.php?file=../../../../../../../../../../etc&do=list


Vulnerable / tested versions:
-----------------------------
The following versions have been tested which were the latest version available 
at the time of the test:

Zeta Producer Desktop CMS 14.1.0
Zeta Producer Desktop CMS 14.2.0

Source: 
- https://www.zeta-producer.com/de/download.html
- https://github.com/ZetaSoftware/zeta-producer-content/


Vendor contact timeline:
------------------------
2017-11-29: Contacting vendor through info@zeta-producer.com and various other
            email addresses from the website. No reply.
2017-12-13: Contacting vendor again, extending email address list, no reply
2018-01-09: Contacting vendor again
2018-01-10: Vendor replies, requests transmission of security advisory
2018-01-10: Sending unencrypted security advisory
2018-07-02: There was no feedback from the vendor but the version 14.2.1 fixed
            the reported vulnerabilities.
2018-07-12: Public advisory release.


Solution:
---------
Upgrade to version 14.2.1 or newer. See the vendor's download page:

https://www.zeta-producer.com/de/download.html

Users of the product also need to verify that the affected widgets are updated in
the corresponding website project! It could be necessary to rebuild the whole project
or copy the new widgets to the website projects. For further information consult the
vendor.


Workaround:
-----------
Remove "formmailer" and "filebrowser" widgets.


Advisory URL:
-------------
https://www.sec-consult.com/en/vulnerability-lab/advisories/index.html