# CVE-2026-43927 — FOSSBilling

> As of 2026-07-07, CVE-2026-43927 is a Medium-severity (band derived from the CVSS v4.0 score, not stated by the CNA) vulnerability in FOSSBilling, CVSS v4.0 6.9, EPSS 0.2% (12.4th percentile). No Threadlinqs-tracked threat campaign has been attributed to CVE-2026-43927 as of 2026-07-07; the identifier is re-checked against the Threadlinqs threat corpus on every daily ingest.

**Last updated:** 2026-07-07

## What is CVE-2026-43927?

FOSSBilling is a free, open-source billing and client management system. Prior to version 0.8.0, a race condition in the cart checkout flow allows an authenticated client to apply a promo code beyond its configured maximum uses. By sending concurrent checkout requests before any single request completes the usage increment, a client can obtain unlimited discounted or free orders from a single-use or limited-use promo code. Version 0.8.0 patches the issue. Some workarounds are available. Disable promo codes entirely until a patch is available or monitor the `promo` table for `used` values exceeding `maxuses` and manually review affected orders.

The record classifies CVE-2026-43927 under weakness class [CWE-367](https://intel.threadlinqs.com/cwe/CWE-367). 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 91 days ago.

## Severity and exploitation probability

- **CVSS v4.0 base score:** 6.9 — Medium (derived from score) (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N`)
- **EPSS (FIRST):** 0.2% probability of exploitation in the next 30 days, higher than 12.4% of all scored CVEs
- **CISA KEV:** Not listed in the CISA Known Exploited Vulnerabilities catalog
- **Threadlinqs priority:** 3.9/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- **Published:** 2026-07-06, last modified 2026-07-07

## Is CVE-2026-43927 being exploited?

It currently carries a trending score of 33 in the Threadlinqs vulnerability feed.

## Affected products and versions

- [FOSSBilling](https://intel.threadlinqs.com/vendors/fossbilling): FOSSBilling

## How to fix CVE-2026-43927

No vendor patch reference has been recorded for CVE-2026-43927 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.

## Threat activity tracking CVE-2026-43927

No threat campaign in the Threadlinqs corpus currently references CVE-2026-43927, in its CVE list or as an indicator. The linkage is recomputed from the live corpus on every daily ingest, so this section fills in as soon as a tracked campaign cites the identifier.

## Sources

Enriched from CVE.org, NVD, FIRST EPSS. Last verified by Threadlinqs on 2026-07-08. This product uses the NVD API but is not endorsed or certified by the NVD.

**Vendor advisory and patch**

- [github.com](https://github.com/FOSSBilling/FOSSBilling/security/advisories/GHSA-w898-cx35-25gh)

Canonical: https://intel.threadlinqs.com/cve/CVE-2026-43927
Full detection coverage and IOCs for threats exploiting CVE-2026-43927 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp