CVE-2026-71537 in Paymenter
Summary
by MITRE • 09/18/2026
Paymenter is a free and open-source webshop solution for management of hosting services. Prior to 1.5.7, app/Livewire/Services/Upgrade.php::doUpgrade() relies on Service::upgradable to check for a pending service upgrade and later executes $credit->increment('amount', abs($price)) without DB::transaction or lockForUpdate() spanning those operations. An authenticated customer with an active downgradable service can submit concurrent downgrade requests that each observe no pending upgrade, create separate upgrade records, and increment the same account credit balance, producing multiple spendable refunds for one downgrade. This issue is fixed in version 1.5.7.
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Analysis
by VulDB Data Team • 09/18/2026
The vulnerability identified within Paymenter versions prior to 1.5.7 represents a critical race condition rooted in improper synchronization of database operations during service upgrade and credit management processes. Paymenter, an open-source webshop solution designed for managing hosting services, contains a flaw in the application logic located at app/Livewire/Services/Upgrade.php::doUpgrade(). The core issue arises from the method's reliance on Service::upgradable to determine if there is a pending service upgrade before proceeding with financial adjustments. This check and the subsequent execution of credit increments are not wrapped within a database transaction or protected by row-level locking mechanisms such as lockForUpdate(). In concurrent environments, this lack of atomicity allows multiple threads or requests from an authenticated user to bypass the intended state checks simultaneously.
An attacker who is an authenticated customer with an active downgradable service can exploit this timing gap by submitting multiple downgrade requests in rapid succession. Because each request independently queries the database and observes that no upgrade record currently exists for the service, all concurrent requests proceed under the false assumption that they are the first to act on the pending state change. Consequently, the application creates separate upgrade records for each request rather than recognizing a single ongoing process. This failure to serialize access leads directly to financial integrity issues where the credit balance is incremented multiple times based on abs($price) calculations derived from the downgrade value. The result is that a user can generate multiple spendable refunds or credits for a single actual service downgrade, effectively inflating their account balance without corresponding legitimate transactions.
From an industry standard perspective, this vulnerability aligns with CWE-362: Concurrent Execution using Shared Resource with Improper Synchronization of Actions. The application fails to properly synchronize access to the shared resource, which is the service upgrade state and associated credit records in the database. Furthermore, the operational impact extends beyond simple financial loss for the merchant; it undermines the integrity of the billing system and can be leveraged for economic abuse or denial of service through resource exhaustion if exploited at scale. The attack vector falls under MITRE ATT&CK technique T1496: Resource Hijacking, specifically in the context of exploiting computational resources to gain unauthorized financial benefits by manipulating state transitions faster than the application can validate them.
Mitigation strategies for this vulnerability involve both immediate patching and long-term architectural improvements. The primary remediation is to upgrade Paymenter to version 1.5.7 or later, where the developers have addressed these synchronization issues. For environments that cannot immediately update, implementing database-level constraints such as unique indexes on service upgrade records can prevent duplicate entries for the same service within a specific timeframe. Additionally, application-layer changes should enforce atomic operations by wrapping the check-for-pending-upgrade and credit-increment logic within explicit database transactions with appropriate isolation levels or row locks. This ensures that only one request can modify the state at any given time, preventing concurrent requests from observing stale data and acting on it simultaneously. Regular security audits focusing on race conditions in financial modules are also recommended to identify similar patterns of unsynchronized shared resource access.