CVE-2026-43927: FOSSBilling has race condition in cart checkout that bypasses promo code usage limits
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 Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
FOSSBillingto a version that resolves this vulnerability.Fixed in 0.8.0 - Configuration
Disable promo codes entirely until a patch is available.
FOSSBilling promo codes = disabled - Compensating control
Monitor the FOSSBilling `promo` table for `used` values exceeding `maxuses` and manually review affected orders.
Event History
Frequently Asked Questions
What is the severity of CVE-2026-43927?
CVE-2026-43927 is rated with a risk level of 40.
How do I fix CVE-2026-43927?
To fix CVE-2026-43927, upgrade to FOSSBilling version 0.8.0 or later.
What type of vulnerability is identified in CVE-2026-43927?
CVE-2026-43927 is classified as a race condition vulnerability.
Who is affected by CVE-2026-43927?
Authenticated clients using versions of FOSSBilling prior to 0.8.0 are affected by CVE-2026-43927.
What specific issue does CVE-2026-43927 allow an attacker to exploit?
CVE-2026-43927 allows an authenticated client to bypass promo code usage limits by exploiting a race condition during cart checkout.