ZTE ZXDSL 831C|| Multiple Vulnerabilities

2:11 PM

ZTE 831CII suffers from login bypass, cross site request forgery, hardcoded administrative credential, and cross site scripting vulnerabilities.

Hardcoded administrative credential 

In ZTE routers the username is a constant which is “admin” and the password by default is “admin”

Insecure Direct Object Reference [CVE-2014-9184]

ZTE ZXDSL 831CII suffers from an insecure direct object reference vulnerability that allows for authentication bypass.

The modem usually serves html files & protects them with HTTP Basic authentication. however, the cgi files, does not get this protection. so simply requesting any cgi file (without no authentication) would give a remote attacker full access to the modem and then can easily be used to root the modem and disrupt network activities.

So requesting gateway (in this case, would result HTTP Authentication request, but simply requesting will bypass it.

PoC: (will result admin password change page) - viewing the source will show the current password (unencrypted)
The page does not contain current password, also have no ani-CSRF token. wtf!

Persistent XSS [CVE-2014-9020];alert%280%29;//&enblUpnp=1&enblLan2=0
Any user browsing to will have a stored xss executed!

XSS'es [CVE-2014-9021]

TR-069 Client page: Stored. executes when users go to;alert%280%29;//&tr69cAcsUser=cpe&tr69cAcsPwd=cpe&tr69cConnReqUser=itms&tr69cConnReqPwd=itms&tr69cNoneConnReqAuth=0&tr69cDebugEnable=0;alert%280%29;//&tr69cAcsPwd=cpe&tr69cConnReqUser=itms&tr69cConnReqPwd=itms&tr69cNoneConnReqAuth=0&tr69cDebugEnable=0;alert%280%29;//&tr69cConnReqUser=itms&tr69cConnReqPwd=itms&tr69cNoneConnReqAuth=0&tr69cDebugEnable=0;alert%280%29;//&tr69cNoneConnReqAuth=0&tr69cDebugEnable=0%27;alert%280%29;//

Time and date page (/sntpcfg.sntp) - Persistent,%20Chongqing,%20Hong%20Kong,%20Urumqi%22;alert%280%29;//&use_dst=0&enblLightSaving=0

Quick Stats page:';alert(0);//&domainname=home&enblUpnp=1&enblLan2=0;alert%280%29;//&enblUpnp=1&enblLan2=0

CSRF based Stored XSS;alert%280%29;//&sysPassword=37F6E6F627B6 - letting an admin visit this link would result the admin username changed to ';alert(0);// also a stored XSS in the home page.

Admin account override CSRF [CVE-2014-9019]

There is no token/capcha or even current password prompt when the admin changes the password, and credentials are sent over GET.
If an authenticated admin browses that link their credentials will become admin:yibelo

UI Redressing

The modem (like most modems) does not have a clickjacking protection. thus, can be used to modify settings, override admin accounts by a simple clickjack. forexample by using it is possible into tricking an admin submit a form with our credintials (since it doesn't require current password)

Not Using SSL

The modem does not use HTTPS, so anyone can use MiTM to sniff ongoing actions, possibly gain user credentials.
Unrestricted privileges
Anyone who is connected to the modem with Telnet or tftp is root. simply telneting and authenticating as admin:admin and typing sh and echo $USER would prove that.

Enable Remote Access CSRF [CVE-2014-9027]

Using this an attacker can trick an admin visit a page that tricks them into enabling remote access to the modem out side of the LAN.
so an attacker can attack the modem out side the lan; then an attacker can use this to escilate the attack.

Enable Access from web browser :80

Enable Access from Telnet :23

Enable Access from TFTP :69

Enable Remote Access from all {80,69,161,23}

and what a fucked up modem I have :'( Good thing I am root.


from all those exploits, its easy to construct a remote root command execution exploit against any of these modems. 

1. Make a logged in admin enable remote access for us with (Only if we are outside LAN)

2.  Go to and change admin password or copy the current one (recommended)
3.  telnet to with the admin password and username (most likely admin:admin) and what do you know,

4. type sh then echo $USER and become the root of the network.

5. RULE'em ALL!

Happy Hacking! :D

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