CVE-2026-18029 in pretix
Summary
by MITRE • 07/28/2026
Our payment integration with GiroCheckout did not properly validate payment status responses. An attacker could use a successful payment status response from one payment and supply it to the system for a different payment, gaining access to multiple valid tickets with only one payment.
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Analysis
by VulDB Data Team • 07/28/2026
This vulnerability represents a critical authorization bypass flaw in the payment processing workflow that directly impacts the integrity of transaction validation mechanisms. The core technical issue stems from inadequate input validation within the payment status response handling logic where the system fails to properly authenticate and verify the authenticity of payment status messages before accepting them as valid. This weakness allows an attacker to exploit a lack of proper correlation between payment identifiers and status responses, effectively enabling replay attacks against the payment processing infrastructure.
The vulnerability can be classified under CWE-284 Access Control Bypass and aligns with ATT&CK technique T1078 Valid Accounts, as it exploits the trust model within the payment system to gain unauthorized access to resources. When a legitimate payment status response is generated by GiroCheckout for one transaction, the system's insufficient validation process permits this response to be reused for different payment identifiers, creating a scenario where multiple valid tickets can be obtained with only a single successful payment attempt. This represents a fundamental breakdown in the payment authorization chain and demonstrates a critical failure in implementing proper session management and transaction correlation mechanisms.
The operational impact of this vulnerability extends beyond simple financial loss to encompass potential system compromise and data integrity issues. Attackers could systematically exploit this flaw to obtain multiple tickets or services without making additional payments, leading to significant revenue loss for the organization. The vulnerability also creates opportunities for more sophisticated attacks where attackers might combine this weakness with other system flaws to escalate their access privileges and potentially gain deeper insights into the payment infrastructure. From a compliance perspective, this vulnerability could result in violations of payment card industry standards such as PCI DSS requirements for proper transaction validation and authorization controls.
Mitigation strategies should focus on implementing robust correlation mechanisms between payment identifiers and status responses, incorporating cryptographic signatures or message authentication codes to validate response authenticity. The system must enforce strict validation of payment identifiers before accepting any status updates, ensuring that each response can only be applied to its corresponding original transaction. Additionally, implementing proper logging and monitoring of payment status changes will help detect unauthorized usage patterns and provide audit trails for forensic analysis. Organizations should also consider implementing rate limiting and anomaly detection mechanisms to identify and block suspicious bulk access patterns that could indicate exploitation attempts. The implementation of these controls aligns with security best practices outlined in NIST SP 800-53 and ISO/IEC 27001 frameworks for payment system security and access control management.