CVE-2018-19249 in Stripe API v1
Summary
by MITRE
The Stripe API v1 allows remote attackers to bypass intended access restrictions by replaying api.stripe.com /v1/tokens XMLHttpRequest data, parsing the response under the object card{}, and reading the cvc_check information if the creation is successful without charging the actual card used in the transaction.
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Analysis
by VulDB Data Team • 04/26/2020
The vulnerability identified as CVE-2018-19249 represents a significant security flaw in the Stripe API v1 implementation that enables unauthorized access to sensitive card information through a sophisticated replay attack mechanism. This vulnerability operates by exploiting the API's response handling behavior when processing token creation requests, specifically targeting the structured response parsing that occurs during card verification processes. The flaw allows malicious actors to construct and replay XMLHttpRequest data to the api.stripe.com/v1/tokens endpoint, effectively bypassing the intended access controls that should prevent unauthorized data retrieval.
The technical exploitation of this vulnerability relies on the improper handling of API responses within the card object structure, particularly when the system processes token creation requests. When an attacker successfully submits a token creation request through the API, the system returns a response containing a card object with specific fields including cvc_check information. This particular field contains crucial verification data that indicates whether the card's security code was successfully validated during the transaction process. The vulnerability exists because the API does not properly validate that the requesting entity has legitimate authorization to access the specific card data being returned in the response, creating a path for information disclosure attacks.
The operational impact of this vulnerability extends beyond simple information leakage, as it enables attackers to perform card validation testing without actually charging cards, effectively creating a reconnaissance mechanism for identifying valid card numbers and their associated security codes. This capability allows threat actors to systematically test large volumes of card data against the Stripe API, potentially identifying which cards have valid security codes and can be used for fraudulent transactions. The vulnerability specifically targets the cvc_check field, which provides critical information about the card's security verification status, making it particularly valuable for attackers seeking to validate card authenticity without triggering fraud detection systems that would normally flag actual charging attempts.
Security implications of CVE-2018-19249 align with CWE-284 (Improper Access Control) and represent a classic case of insufficient authorization checks in API response handling. The vulnerability demonstrates how API implementations can inadvertently expose sensitive data through response parsing mechanisms, particularly when the system does not properly validate that the requesting entity has appropriate authorization levels to access specific data elements within structured responses. This weakness enables attackers to leverage legitimate API functionality to extract information that should remain protected, creating a scenario where the API's intended security controls are effectively bypassed through clever manipulation of request and response patterns.
The attack vector for this vulnerability operates through the manipulation of XMLHttpRequest data that targets the specific API endpoint structure at api.stripe.com/v1/tokens, where the system's response parsing behavior creates the information disclosure opportunity. This attack model fits within the ATT&CK framework under the T1071.004 technique for Application Layer Protocol: DNS, as it exploits legitimate API protocols to achieve unauthorized data access. The vulnerability's exploitation requires minimal privileges and can be automated, making it particularly dangerous for organizations that rely on Stripe's payment processing services for handling sensitive cardholder data.
Mitigation strategies for CVE-2018-19249 should focus on implementing robust authorization checks at the response level, ensuring that API responses contain only information that the requesting entity should legitimately access. Organizations should enforce proper access control validation before returning any card-related information in API responses, particularly fields like cvc_check that provide verification status information. The implementation of request/response validation mechanisms that verify the authenticity and authorization level of requesting entities before exposing sensitive data elements represents the most effective countermeasure. Additionally, organizations should consider implementing rate limiting and anomaly detection for API access patterns that might indicate automated exploitation attempts, as the vulnerability's exploitation typically involves systematic testing of multiple card combinations through the API.