PayPal QR Labs Authentication Bypass

`Title:  
======  
Paypal Bug Bounty #102 QR Dev Labs - Auth Bypass Vulnerability  
  
  
Date:  
=====  
2013-07-05  
  
  
References:  
===========  
http://www.vulnerability-lab.com/get_content.php?id=995  
  
PayPal Security UID: ZVf25kC  
  
  
VL-ID:  
=====  
995  
  
  
Common Vulnerability Scoring System:  
====================================  
7.1  
  
  
Introduction:  
=============  
Shopping made easy with PayPal QR enabled on your mobile device. You can scan for deals using the QR Code displayed in shops,   
trains stations, bus-stops & banners and purchase items in just a few taps. Make shopping experience easy for your customer.  
  
(Copy of the Vendor Homepage: https://qr.paypal-labs.com )  
  
  
Abstract:  
=========  
An independent vulnerability laboratory researcher discovered an auth bypass web session vulnerability in the PayPal QR Labs Service Web Application.  
  
  
Report-Timeline:  
================  
2012-05-11: Researcher Notification & Coordination (Cernica Ionut)  
2013-05-14: Vendor Notification (PayPal Inc Security Incident Team - Bug Bounty Program)  
2013-06-20: Vendor Fix/Patch (PayPal Inc Developer Team)  
2013-07-05: Public Disclosure (Vulnerability Laboratory)  
  
  
Status:  
========  
Published  
  
  
Affected Products:  
==================  
PayPal Inc  
Product: QR Labs Online Service - Web Application 2013 Q2  
  
  
Exploitation-Technique:  
=======================  
Remote  
  
  
Severity:  
=========  
High  
  
  
Details:  
========  
An auth bypass session web vulnerability is detected in the official PayPal QR Labs Service Web Application.  
The vulnerability allows remote attackers to bypass the web- or system user auth of the affected   
vulnerable computer system to compromise paypal accounts.  
  
The bug is located in the application account login module when processing to load manipulated j_password   
parameters via GET method. Attackers are able the decrypt and exchange the information in the request live   
with a session tamper to take-over other accounts. At the end the vulnerability allows remote attackers to   
enter remotely any paypal qr labs account of the web application.  
  
Exploitation of the vulnerability does not require user interaction but a low privileged paypal qr labs   
application user account. Successful exploitation results in account steal or compromise and stable user   
session manipulation with different effects.  
  
Vulnerable Service(s):  
[+] PayPal Inc – qr.paypal-labs.com  
  
Vulnerable Module(s):  
[+] Account - Login  
  
Vulnerable Parameter(s):  
[+] j_password  
  
Affected Module(s):  
[+] Account System  
  
  
Proof of Concept:  
=================  
The vulnerability can be exploited by remote attackers with low privilege paypal qr labs application user account and   
without user interaction. For demonstration or reproduce ...  
  
Note:  
After some security checks to authenticate in the qr.paypal-labs.com web application, the last request for being authenticate   
in this web application it is not secure implemented.  
  
Afected Link:  
https://qr.paypal-labs.com/[email protected]&j_password=96301aa9f02b5d12278b0e902dc5434ed9477d19  
  
Note:  
If we look at the request wich is a GET method request we will soon see ...  
If we encrypt the j_username parameter value as SHA1 ...   
The result will be the value of the j_password parameter  
  
Note: PoC Video  
The username [email protected] is encrypted in SHA1 it is equals with < 96301aa9f02b5d12278b0e902dc5434ed9477d19  
In the demonstration above it seems that the password of the username is encrypted in SHA1 ;)  
  
  
Solution:  
=========  
2013-06-20: Vendor Fix/Patch (PayPal Inc Developer Team)  
  
  
Risk:  
=====  
The security risk of the auth bypass web session vulnerability is estimated as high(+).  
  
  
Credits:  
========  
Independent Security Researcher – Cernica Ionut Cosmin ([email protected])  
  
  
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===========  
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