CVE-2011-3682: 2WIRE-SINGTEL 2701HGV-E/2700HGV-2/2700HG GATEWAY ROUTER MANAGEMENT AND DIAGNOSTIC CONSOLE VULNERABILITY

[tan@xxxxxxxxxxxx]

CVE-2011-3682: 2WIRE-SINGTEL 2701HGV-E/2700HGV-2/2700HG GATEWAY ROUTER 
MANAGEMENT AND DIAGNOSTIC CONSOLE VULNERABILITY 


1.      BACKGROUND AND AFFECTED MODELS/FIRMWARE 

SingTel provides customized versions of 2Wire gateway routers to its Internet 
service subscribers for the purpose of accessing the web. 

Customized firmware at major version 5 (or below) contains a Management and 
Diagnostic Console (MDC) at http://192.168.1.254/mdc (when accessing from a 
device connected to the router) for SingTel engineers to perform setup and 
debugging procedures. 

While the vulnerability is known to be patched in major version 6 (and above) 
of the firmware, it is likely that a high number of SingTel Internet service 
customers are still on the outdated firmware as there is no firmware upgrade 
procedure available to these subscribers. 

2.      VULNERABILITY

The MDC has its default password set as ?2wire?. As opposed to the user panel 
at http://192.168.1.254, this password cannot be changed. 

Although the site is only accessible through devices on the local subnet of the 
router, when combined with the lack of Cross-Site Request Forgery (CSRF) 
protection, the vulnerability allows attackers to alter the router?s settings 
for malicious purposes. 

3.      EXPLOIT

The exploit can be delivered through a HTML page served to the victim. Then, 
the maliciously crafted page can instruct the victim?s browser to send a POST 
request, meant to execute changes in the MDC, via XMLHttpRequest or a populated 
and automatically submitted form in JavaScript. 

For instance, in the proof-of-concept, which reboots the router when served to 
a client connected to a vulnerable router, a form is POST to 
http://192.168.1.254/xslt with the following parameters: 

PAGE = S01_POST, 
view = XML, 
THISPAGE = J21, 
NEXTPAGE = J21_REBOOT, 
PASSWORD = 2wire 

4.      IMPACTS AND ADVISORY

A successful attack is unlikely to be noticed by the end-user with the lack of 
warning that comes with a CSRF attack, especially when performed through 
XMLHttpRequest. A likely exploitation would involve the alteration of the 
victim router?s Domain Name System (DNS) records, enabling a Man-in-the-Middle 
(MITM) attack vector. This allows for severe Advanced Persistent Threats (APT) 
to the victim. 

Hence, it is advised for SingTel and 2Wire to push the updated firmware to its 
subscribers as soon as possible. 

While the issue is pending resolution, SingTel Internet service customers with 
firmware major version 5 (and below) are advised to: 

-       Avoid visiting any website that is not previously trusted, especially 
web search results and links on social networking sites 
-       Pay increased attention to any anomalies in Internet service, such as 
substantial increase in page-load durations 

5.      DISCLOSURE AND NOTES 

Attempt has been made to contact SingTel about the vulnerability through 
SingCERT on 14 September 2011. While confirmation of vulnerability has been 
received, no plan to fix the vulnerability has been made known before the 31 
October 2011 deadline specified. 


TAN SZE CHUEN 
Security Researcher 
tan@xxxxxxxxxxxx (PGP key available) 


Updates and Proof-of-Concept at http://blog.szechuen.com/cve-2011-3682