PayPal Bug Bounty #110 - Auth Bypass (Session) Vulnerability

[Vulnerability Lab <research@xxxxxxxxxxxxxxxxxxxxx>]

Title:
======
PayPal Bug Bounty #110 - Auth Bypass (Session) Vulnerability


Date:
=====
2013-08-21


References:
===========
http://www.vulnerability-lab.com/get_content.php?id=1056

PayPal Security UID:  oebaLK


VL-ID:
=====
1056


Common Vulnerability Scoring System:
====================================
9.1


Introduction:
=============
PayPal is a global e-commerce business allowing payments and money transfers to 
be made through the Internet. Online money
transfers serve as electronic alternatives to paying with traditional paper 
methods, such as checks and money orders. Originally,
a PayPal account could be funded with an electronic debit from a bank account 
or by a credit card at the payer s choice. But some
time in 2010 or early 2011, PayPal began to require a verified bank account 
after the account holder exceeded a predetermined
spending limit. After that point, PayPal will attempt to take funds for a 
purchase from funding sources according to a specified
funding hierarchy. If you set one of the funding sources as Primary, it will 
default to that, within that level of the hierarchy
(for example, if your credit card ending in 4567 is set as the Primary over 
1234, it will still attempt to pay money out of your
PayPal balance, before it attempts to charge your credit card). The funding 
hierarchy is a balance in the PayPal account; a
PayPal credit account, PayPal Extras, PayPal SmartConnect, PayPal Extras Master 
Card or Bill Me Later (if selected as primary
funding source) (It can bypass the Balance); a verified bank account; other 
funding sources, such as non-PayPal credit cards.
The recipient of a PayPal transfer can either request a check from PayPal, 
establish their own PayPal deposit account or request
a transfer to their bank account.

PayPal is an acquirer, performing payment processing for online vendors, 
auction sites, and other commercial users, for which it
charges a fee. It may also charge a fee for receiving money, proportional to 
the amount received. The fees depend on the currency
used, the payment option used, the country of the sender, the country of the 
recipient, the amount sent and the recipient s account
type. In addition, eBay purchases made by credit card through PayPal may incur 
extra fees if the buyer and seller use different currencies.

On October 3, 2002, PayPal became a wholly owned subsidiary of eBay. Its 
corporate headquarters are in San Jose, California, United
States at eBay s North First Street satellite office campus. The company also 
has significant operations in Omaha, Nebraska, Scottsdale,
Arizona, and Austin, Texas, in the United States, Chennai, Dublin, Kleinmachnow 
(near Berlin) and Tel Aviv. As of July 2007, across
Europe, PayPal also operates as a Luxembourg-based bank.

On March 17, 2010, PayPal entered into an agreement with China UnionPay (CUP), 
China s bankcard association, to allow Chinese consumers
to use PayPal to shop online.PayPal is planning to expand its workforce in Asia 
to 2,000 by the end of the year 2010.
Between December 4ñ9, 2010, PayPal services were attacked in a series of 
denial-of-service attacks organized by Anonymous in retaliation
for PayPal s decision to freeze the account of WikiLeaks citing terms of use 
violations over the publication of leaked US diplomatic cables.

(Copy of the Homepage: www.paypal.com) [http://en.wikipedia.org/wiki/PayPal]


Abstract:
=========
An independent vulnerability laboratory researcher discovered a Web 
Vulnerability in the PayPal QR Labs Service Web Application.



Report-Timeline:
================
2012-04-27:    Researcher Notification & Coordination (Cernica Ionut)
2013-04-28:    Vendor Notification (PayPal Inc Security Incident Team - Bug 
Bounty Program)
2013-05-05:    Vendor Response (PayPal Inc Security Incident Team - Bug Bounty 
Program)
2013-08-20:    Vendor Fix/Patch (PayPal Inc Developer Team - Bug Bounty Program 
Reward)
2013-08-21:    Public Disclosure (Vulnerability Laboratory)


Status:
========
Published


Affected Products:
==================
PayPal Inc
Product: PayPal Account Service Application 2013 Q2


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


Severity:
=========
Critical


Proof of Concept:
=================
The vulnerability can be exploited by remote attackers with low privilege 
paypal application user account and 
without user interaction. For demonstration or reproduce ...

After testing the web application paypal.com I discovered that if you have an 
US account and the following page 
is visited 
(https://www.paypal.com/us/cgi-bin/?&cmd=_bc-signup&channel=1&promo=503), you 
can add a new email from 
that page. The problem is even the e-mail you try to add to your account is 
already registered with paypal the 
new e-mail will be added into your account as unconfirmed.

Delete any account on PayPal:
After you added an existing email to your account if you go to the account 
profile an you delete the unconfirmed 
email, the original account will be deleted too.

Auth Bypass:
After you removed the account, you can make another one with same username with 
your desired password, but you will
have no money and is not confirmed.

video P.o.C.:
http://www.youtube.com/watch?feature=player_embedded&v=Txj_uFYTVuo


Solution:
=========
2013-08-20:    Vendor Fix/Patch (PayPal Inc Developer Team - Bug Bounty Program 
Reward)


Risk:
=====
The security risk of the session account auth bypass vulnerability is estimated 
as critical.


Credits:
========
Independent Security Researcher – Cernica Ionut Cosmin 
(ionut.cernica@xxxxxxxxxxxx)


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===========
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