CVE-2026-119421 in Hyperswitch
Summary
by MITRE • 10/30/2026
Juspay Hyperswitch through 1.128.0 (and builds before 2026.10.19.0) contains a missing authorization vulnerability that allows unauthenticated attackers to confirm payouts with any client_secret via POST /payouts/{payout_id}/confirm. Attackers holding the merchant's publishable key and a payout_id can confirm payouts and overwrite amount, currency, connector, and routing fields to trigger unauthorized merchant payouts.
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Analysis
by VulDB Data Team • 10/30/2026
The vulnerability identified in Juspay Hyperswitch versions up to 1.128.0 represents a critical failure in access control mechanisms within the payment processing API. Specifically, this flaw resides in the endpoint responsible for confirming payout transactions, located at POST /payouts/{payout_id}/confirm. The core technical deficiency is a missing authorization check that fails to validate whether the client_secret provided during the request corresponds to the specific merchant or entity associated with the target payout identifier. In secure payment architectures, every API call involving financial movement must enforce strict binding between the authentication credentials and the resource being accessed. Here, the system incorrectly accepts any validly formatted client_secret alongside a known payout_id, effectively decoupling identity verification from transaction authorization. This architectural oversight allows an attacker who possesses only the merchant's publishable key—which is generally considered less sensitive than secret keys—and a specific payout identifier to manipulate and finalize financial transactions without proper permission checks.
From a technical perspective, this vulnerability enables unauthenticated actors to execute unauthorized modifications to critical payment parameters. By leveraging the flawed confirmation endpoint, attackers can overwrite essential fields such as the transaction amount, currency type, payment connector selection, and routing rules. This capability transforms what should be a simple status update into a mechanism for financial fraud. The attacker does not need to compromise the merchant's secret key or bypass complex cryptographic signatures; they merely need to supply any client_secret that is accepted by the system alongside the target payout_id. Once these fields are manipulated, the system processes the transaction as if it were authorized by the legitimate account holder, leading directly to unauthorized fund transfers. This type of flaw is particularly dangerous in payment gateways because it bypasses the fundamental principle of least privilege and fails to ensure that only intended parties can initiate or confirm financial movements.
The operational impact of this vulnerability is severe, resulting in direct financial loss for merchants and potential reputational damage for Juspay Hyperswitch as a service provider. Attackers can drain merchant accounts by confirming payouts with altered amounts or routing funds through unintended connectors, potentially facilitating money laundering or fraud schemes. Because the publishable key is often exposed on client-side applications or public-facing interfaces, it provides an easy entry point for reconnaissance and exploitation. The ability to change currency and connector fields further complicates detection efforts, as transactions may appear legitimate in logs but route funds differently than intended by the merchant's configuration. This lack of integrity control means that even if authentication occurs at a higher level, the specific action of confirming a payout remains unprotected against unauthorized modification.
This vulnerability aligns with CWE-284, which describes Improper Access Control, specifically where access controls are not properly enforced for critical functions involving financial transactions. It also maps to MITRE ATT&CK techniques related to Account Manipulation and potentially T1530 if the attacker uses stolen credentials or keys to exfiltrate data or funds. The failure to bind the client_secret strictly to the specific payout resource violates standard security practices outlined in OWASP API Security Top 10, particularly under categories concerning Broken Object Level Authorization (BOLA) and insufficient input validation for critical business logic.
To mitigate this risk, immediate action is required to patch the authorization logic within the Hyperswitch codebase. The system must be updated to enforce strict verification that the client_secret presented in the request matches the secret key associated with the merchant account linked to the specific payout_id. This involves implementing robust object-level access controls where every API endpoint validates ownership of the resource being modified before allowing state changes such as confirmation or cancellation. Additionally, developers should implement rate limiting and anomaly detection on the payouts endpoint to identify unusual patterns of activity that may indicate exploitation attempts. Merchants using affected versions must upgrade immediately to a patched release released after October 19, 2026, or build version 2026.10.19.0 and above. Until patching is complete, merchants should monitor their transaction logs for unexpected payout confirmations and consider temporarily restricting access to the payouts API if possible through network-level controls while awaiting the software update.