CVE-2026-55219 in Paymenter
Summary
by MITRE • 07/21/2026
Paymenter is a free and open-source webshop solution for management of hosting services. In versions prior to 1.5.5, the credit payment implementation in app/Livewire/Invoices/Show.php executes a pessimistic row lock (lockForUpdate()) outside of an active database transaction. Because MySQL/MariaDB requires an enclosing transaction to enforce row-level locks, the guard is ineffective. Concurrent payment requests can exploit this race condition to read the same credit balance simultaneously, allowing users to pay multiple invoices using the same credit balance. In database systems like MySQL, a row lock only works inside a formal transaction; without one, the lock is completely ignored. Because there is no active lock, two payment requests sent at the exact same millisecond can look at the database at the same time. Both requests see the original credit balance, decide it is sufficient, and approve the payment. Because the payment processes successfully through ExtensionHelper::addPayment(), the application provisions the corresponding services or digital goods, resulting in direct financial or resource loss to the platform. This issue has been fixed in version 1.5.5.
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Analysis
by VulDB Data Team • 07/21/2026
The Paymenter webshop solution presents a critical race condition vulnerability in its credit payment implementation that stems from improper database transaction handling. This flaw exists in versions prior to 1.5.5 within the app/Livewire/Invoices/Show.php file where the system attempts to implement a pessimistic row lock using lockForUpdate() method. The fundamental issue occurs because the application executes this locking mechanism outside of an active database transaction context, creating a scenario where the database engine cannot properly enforce the intended concurrency controls.
The technical root cause of this vulnerability aligns with CWE-362, which describes a race condition error where two or more processes access shared resources concurrently without proper synchronization. In MySQL and MariaDB environments, row-level locks only function correctly within explicit database transactions as defined by the SQL standard. When lockForUpdate() is called outside of a transaction block, the database engine simply ignores the locking directive, rendering it ineffective for preventing concurrent access to sensitive data.
This vulnerability creates a direct financial risk through a classic double-spending scenario where multiple payment requests can simultaneously read identical credit balances. The race condition manifests when two or more concurrent requests arrive at precisely the same millisecond, both observing the initial credit balance value and proceeding with payment processing. Since each request validates against the same unmodified balance figure, they all pass the validation check and successfully process payments through the ExtensionHelper::addPayment() function.
The operational impact of this vulnerability extends beyond simple financial loss to encompass potential resource exhaustion and service provisioning abuse. When multiple payment requests successfully complete processing, the platform incorrectly provisions services or digital goods for each transaction, resulting in direct revenue loss and potential system instability. This creates a cascading effect where legitimate users may experience service disruption while malicious actors can exploit the flaw for unauthorized resource consumption.
The fix implemented in version 1.5.5 addresses this issue by ensuring that all database row locking operations occur within proper transaction boundaries. This remediation follows established best practices for concurrent database access control and aligns with ATT&CK technique T1496 which covers resource hijacking through improper access controls. The solution requires that lockForUpdate() calls be wrapped within explicit database transactions, ensuring that MySQL/MariaDB properly enforces row-level locking mechanisms and prevents the race condition from occurring.
Security practitioners should note this vulnerability as a prime example of how seemingly simple concurrency control mechanisms can fail catastrophically when not implemented according to database engine requirements. The attack surface is particularly concerning for payment processing systems where financial integrity is paramount, making proper transaction handling and lock management critical components of secure application design. Organizations using Paymenter or similar systems should prioritize immediate patching to prevent exploitation of this vulnerability that could result in significant financial losses and operational disruptions.