What’s Vulnerable › Vulnerabilities
CVE-2026-43927: FOSSBilling has race condition in cart checkout that bypasses promo code usage limits
- Severity: medium (CVSS 6.9 v4.0)
- Exploited in the wild: not listed in CISA KEV
- EPSS: 0.3% probability of exploitation in the next 30 days
- Public exploit or detection template: none known
- Published: 2026-07-06 · updated 2026-07-07
- Weakness: CWE-367
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
- FOSSBilling: before 0.8.0
References
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