ADB Authorization Bypass

`SEC Consult Vulnerability Lab Security Advisory < 20180704-1 >  
=======================================================================  
title: Authorization Bypass  
product: All ADB Broadband Gateways / Routers  
(based on Epicentro platform)  
vulnerable version: Hardware: ADB P.RG AV4202N, DV2210, VV2220, VV5522, etc.  
fixed version: see "Solution" section below  
CVE number: CVE-2018-13109  
impact: critical  
homepage: http://www.adbglobal.com  
found: 2016-06-28  
by: Johannes Greil (Office Vienna)  
SEC Consult Vulnerability Lab  
  
An integrated part of SEC Consult  
Europe | Asia | North America  
  
https://www.sec-consult.com  
=======================================================================  
  
Vendor description:  
-------------------  
"ADB creates and delivers the right solutions that enable our customers to  
reduce integration and service delivery challenges to increase ARPU and reduce  
churn. We combine ADB know-how and products with those from a number of third  
party industry leaders to deliver complete solutions that benefit from  
collaborative thinking and best in class technologies."  
  
Source: https://www.adbglobal.com/about-adb/  
  
"Founded in 1995, ADB initially focused on developing and marketing software  
for digital TV processors and expanded its business to the design and  
manufacture of digital TV equipment in 1997. The company sold its first set-top  
box in 1997 and since then has been delivering a number of set-top boxes, and  
Gateway devices, together with advanced software platforms. ADB has sold over  
60 million devices worldwide to cable, satellite, IPTV and broadband operators.  
ADB employs over 500 people, of which 70% are in engineering functions."  
  
Source: https://en.wikipedia.org/wiki/Advanced_Digital_Broadcast  
  
  
Business recommendation:  
------------------------  
By exploiting the authorization bypass vulnerability on affected and unpatched  
devices an attacker is able to gain access to settings that are otherwise  
forbidden for the user, e.g. through strict settings set by the ISP. It is also  
possible to manipulate settings to e.g. enable the telnet server for remote  
access if it had been previously disabled by the ISP. The attacker needs some  
user account, regardless of the permissions, for login, e.g. the default one  
provided by the ISP or printed on the device can be used.  
  
  
It is highly recommended by SEC Consult to perform a thorough security review  
by security professionals for this platform. It is assumed that further critical  
vulnerabilities exist within the firmware of this device.  
  
  
Vulnerability overview/description:  
-----------------------------------  
1) Authorization bypass vulnerability (CVE-2018-13109)  
Depending on the firmware version/feature-set of the ISP deploying the ADB  
device, a standard user account may not have all settings enabled within  
the web GUI.  
  
An authenticated attacker is able to bypass those restrictions by adding a  
second slash in front of the forbidden entry of the path in the URL.  
It is possible to access forbidden entries within the first layer of the web  
GUI, any further subsequent layers/paths (sub menus) were not possible to access  
during testing but further exploitation can't be ruled out entirely.  
  
  
Proof of concept:  
-----------------  
1) Authorization bypass vulnerability (CVE-2018-13109)  
Assume the following URL is blocked/forbidden within the web GUI settings:  
http://$IP/ui/dboard/settings/management/telnetserver  
  
Adding a second slash in front of the blocked entry "telnetserver" will enable  
full access including write permissions to change settings:  
http://$IP/ui/dboard/settings/management//telnetserver  
  
This works for many other settings within the web GUI!  
  
  
In our tests it was not possible to access subsequent layers, e.g.:  
Assume that both the proxy menu and submenu "rtsp" settings are blocked,  
a second slash will _not_ enable access to the RTSP settings:  
http://$IP/ui/dboard/settings/proxy//rtsp  
  
Nevertheless, it can't be ruled out that sub menus can be accessed too when  
further deeper tests are being performed.  
  
  
Vulnerable / tested versions:  
-----------------------------  
The following devices & firmware have been tested which were the most recent  
versions at the time of discovery:  
  
The firmware versions depend on the ISP / customer of ADB and may vary!  
  
ADB P.RG AV4202N - E_3.3.0, latest firmware version, depending on ISP  
ADB DV 2210 - E_5.3.0, latest firmware version, depending on ISP  
ADB VV 5522 - E_8.3.0, latest firmware version, depending on ISP  
ADB VV 2220 - E_9.0.6, latest firmware version, depending on ISP  
etc.  
  
It has been confirmed by ADB that _all_ their ADB modems / gateways / routers  
based on the Epicentro platform are affected by this vulnerability in all  
firmware versions for all their customers (ISPs) at the time of identification  
of the vulnerability _except_ those devices which have a custom UI developed  
for the ISP.  
  
  
Vendor contact timeline:  
------------------------  
2016-07-01: Contacting vendor ADB, sending encrypted advisory, asking about  
affected devices  
2016-07-08: Receiving information about affected devices  
2016-07 - 2017-04: Further coordination, waiting for firmware release,  
implementation & rollout phases for their customers  
2018-07-04: Embargo lifted, public release of security advisory  
  
  
Solution:  
---------  
The firmware versions depend on the ISP / customer of ADB and may vary!  
  
Patch version:  
  
ADB P.RG AV4202N >= E_3.3.2, firmware version depending on ISP  
ADB DV2210 >= E_5.3.2, firmware version depending on ISP  
ADB VV5522 >= E_8.3.2, firmware version depending on ISP  
ADB VV2220 >= E_9.3.2, firmware version depending on ISP  
etc.  
  
  
Workaround:  
-----------  
Restrict access to the web interface and only allow trusted users.  
Change any default/weak passwords to strong credentials.  
Don't allow remote access to the web GUI via Internet.  
  
  
Advisory URL:  
-------------  
https://www.sec-consult.com/en/vulnerability-lab/advisories/index.html  
  
  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
  
SEC Consult Vulnerability Lab  
  
SEC Consult  
Europe | Asia | North America  
  
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  
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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.  
  
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EOF J. Greil / @2018  
  
`