Yahoo Bug Bounty #37 - Sender Spoofing Vulnerability

[Vulnerability Lab <research () vulnerability-lab com>]

Document Title:
===============
Yahoo Bug Bounty #37 - Sender Spoofing Vulnerability 


References (Source):
====================
http://www.vulnerability-lab.com/get_content.php?id=1781


Release Date:
=============
2016-03-07


Vulnerability Laboratory ID (VL-ID):
====================================
1777


Common Vulnerability Scoring System:
====================================
3


Product & Service Introduction:
===============================
Yahoo Inc. (styled as Yahoo!) is an American multinational technology company headquartered in Sunnyvale, California. 
It is globally 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.[9] According to third-party web analytics providers, Alexa and SimilarWeb, Yahoo! 
is the highest-read news 
and media website, with over 7 billion readers per month, being the fourth most visited website globally, as of June 
2015.[8][10][11] 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. Yahoo was founded by Jerry Yang and David Filo in January 1994 and was 
incorporated on March 1, 1995. Marissa 
Mayer, a former Google executive, serves as CEO and President of the company.

(Copy of the Homepage: https://en.wikipedia.org/wiki/Yahoo! )


Abstract Advisory Information:
==============================
An independent vulnerability laboratory researcher discovered a mail spoofing vulnerability in the official Yahoo 
classic online service web-application.


Vulnerability Disclosure Timeline:
==================================
2015-10-17: Researcher Notification & Coordination (Lawrence Amer)
2015-10-18: Vendor Notification (Yahoo Security Incident Team)
2015-10-25: Vendor Response/Feedback (Yahoo Security Incident Team)
2016-02-29: Vendor Fix/Patch (Yahoo Developer Team)
2016-02-29: Security Acknowledgements (Yahoo Security Incident Team)
2016-03-07: Public Disclosure (Vulnerability Laboratory)


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


Affected Product(s):
====================

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


Severity Level:
===============
Medium


Technical Details & Description:
================================
Remote attackers are able to spoof the sender name of yahoo email users to send a spoofed sender with spoofed content. 
After investigation in the vulnerability we discovered that it is located in the yahoo classic web application product. 
Attackers are able to perform the malicious interaction via the yahoo classic mail service. The vulnerability is 
located 
in the `compose message` module of the web service. The request method to inject or intercept as reply is POST.

Affected Module(s): 
                                [+] Message compose [yahoo classic version] 

Affected Parameter(s):
                                [+] from addresses [sender name] 



Proof of Concept (PoC):
=======================
The vulnerability can be exploited by remote attackers without privileged web-application user account or user 
interaction.
For security demonstration or to reproduce the web vulnerability follow the provided information and steps below to 
continue. 

Manual steps to reproduce the vulnerability ...
1. Login to attacker email address . change the mod of yahoo to classic one 
2. Attacker intercept the sending data and change the parameter [from address 'send name '] to any desired name like " 
yahoo security " 
3. User receives a message as from yahoo security spoofing sender name 
4. Successful reproduce of the vulnerability!

PoC: Video
https://www.youtube.com/watch?v=tD7XmyF83NM


Solution - Fix & Patch:
=======================
The fix can be made by disallowing users to change or to edit the sender names in the main POST/GET method requests at 
all. 


Security Risk:
==============
The security risk of the spoofing web vulnerability in the yahoo classic service is estimated as medium. (CVSS 3.0)


Credits & Authors:
==================
Vulnerability Laboratory [Research Team] - Lawrence Amer - 
http://www.vulnerability-lab.com/show.php?user=Lawrence%20Amer



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