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@vulnerability-lab.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 if Vulnerability-Lab or its suppliers have been advised of the possibility of such damages. Some states do not allow the exclusion or limitation of liability for consequential or incidental damages so the foregoing limitation may not apply. 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