BugTraq
Paypal Inc Bug Bounty #36 - SecurityKey Card Serialnumber Module Vulnerability Jun 18 2014 01:32PM
Vulnerability Lab (research vulnerability-lab com)
Document Title:
===============
Paypal Inc Bug Bounty #36 - SecurityKey Card Serialnumber Module Vulnerability

References (Source):
====================
http://www.vulnerability-lab.com/get_content.php?id=834

Release Date:
=============
2014-06-18

Vulnerability Laboratory ID (VL-ID):
====================================
834

Common Vulnerability Scoring System:
====================================
4.3

Product & Service 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.

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

Abstract Advisory Information:
==============================
The Vulnerability Laboratory Research Team discovered a persistent input validation web vulnerability in the official PayPal Inc web-application & api.

Vulnerability Disclosure Timeline:
==================================
2012-10-26: Researcher Notification & Coordination (Benjamin Kunz Mejri)
2012-10-27: Vendor Notification (PayPal Inc Site Security Team - Bug Bounty Program)
2012-10-28: Vendor Response/Feedback (PayPal Inc Site Security Team - Bug Bounty Program)
2013-08-12: Vendor Fix/Patch (PayPal Inc - Develoepr Team)
2014-06-18: Public Disclosure (Vulnerability Laboratory)

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

Affected Product(s):
====================
PayPal Inc
Product: PayPal Account Service Application 2013 Q4

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

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

Technical Details & Description:
================================
An application-side validation web vulnerability has been discovered in the official PayPal Inc web-application and api.
The vulnerability allows remote attackers to inject own malicious arbitrary codes on the application-side of the service.

The input of the paypal security card serialnumber does not validate special chars. Regular the serialnumber must be
an integer value (numbers). In case of the vulnerable input attackers are able to use 2 x 6 char long pin codes to save
a not secure encoded serialnumber input. The validation of the serialnumber input field should use the same char restriction
on input like the pin code input fields to prevent. During the testings we ordered a secure paypal pin card for payments with
a malicious test payload in the stored serialnumber value. In case of a real attack scenario the attacker had all abilities
to order cards with manipulated serial numbers. The attack vector of the vulnerability is on the application-side of the
paypal online-service and the request method to inject is POST.

The security risk of the application-side validation vulnerability in the security card system module is estimated as medium
with a cvss (common vulnerability scoring system) count of 4.3.

Exploitation of the application-side validation vulnerability requires a low privileged paypal account with restricted access
and no user interaction. Successful exploitation of the vulnerability results in security card system manipulation/compromise,
card serialnumber compromise and sessionhijacking.

Request Method(s): Inject
[+] POST

Vulnerable Module(s):
[+] PayPal SecurityKey (Card Service)

Vulnerable Parameter(s): Input
[+] Serialnumber (Seriennummer)

Affected Service(s):
[+] PayPal SecurityKey Card < Serialnumber (Seriennummer)

Solution - Fix & Patch:
=======================
The vulnerability can be patched by a secure parse and encode of the vulnerable serialnumber input field.

Security Risk:
==============
The security risk of the persistent validation web vulnerability in the serialnumber input is estimated as medium.

Credits & Authors:
==================
Vulnerability Laboratory [Research Team] - Benjamin Kunz Mejri (bkm (at) vulnerability-lab (dot) com [email concealed]) [www.vulnerability-lab.com]

Disclaimer & Information:
=========================
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