Vulnerability · Published Jul 6, 2026 · Assigned by GitHub_M
CVE-2026-43927FOSSBilling has race condition in cart checkout that bypasses promo code usage limits
Medium 6.9
In plain English
A medium-severity security flaw in FOSSBilling from FOSSBilling. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 26% of all known vulnerabilities).
Official description
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.
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| FOSSBilling | FOSSBilling | < 0.8.0 |
Weakness: CWE-367 · Vector: 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