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GHSA-5gmm-hjfj-8ff7
paymenter/paymenterSummary
The service downgrade implementation in app/Livewire/Services/Upgrade.php::doUpgrade() executes a proration calculation and a subsequent user credit refund without any transactional safety or database locks. The only concurrency check relies on an unisolated database query checking for existing pending upgrades. Because there is no active database transaction or pessimistic row-level lock spanning this validation and the subsequent credit update, concurrent downgrade requests can bypass the guard simultaneously. This allows a user to trigger multiple refunds for a single service downgrade.
Technical Details
The issue occurs because the application verifies eligibility using an unlocked read operation (Service::upgradable) which checks if a pending upgrade row exists. Since there is no enclosing DB::transaction or lockForUpdate(), multiple requests sent in parallel can all query the database at the same millisecond, observe that no pending upgrade exists, and pass the safety check.
Once passed, each concurrent request inserts its own pending upgrade record and executes $credit->increment('amount', abs($price)). Because the balance updates are not serialized against the initial check, the user's credit balance is cumulatively inflated by $N$ times the refund amount for a single legitimate downgrade.
Impact
This race condition allows any authenticated customer with an active, downgradable service to inflate their spendable credit balance to an arbitrary multiple of their legitimate refund amount.
Because the newly granted balance acts as real, spendable store credit, it can be immediately leveraged to settle future platform invoices or provision additional services, resulting in direct financial and resource loss to the operator.
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The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker needs basic access or low-level privileges. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a high impact on the integrity of the data.
Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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