CVE-2026-43927Network attack vector

Discounted-order creation via non-atomic promo counter

Published Jul 6, 2026 · Updated Jul 6, 2026

Race condition in FOSSBilling before 0.8.0 allows remote authenticated users to exceed promo-code use limits during checkout. In Cart Service.php, promoCanBeApplied reads and checks the used counter separately from usePromo, which increments and stores it without locking, a transaction, or an atomic update. An authenticated client and an enabled limited-use promo code are required; concurrent requests can create unlimited discounted or free orders.

CVSS severity6.9
Medium
EPSS probability0.33%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Race condition in FOSSBilling before 0.8.0 allows remote authenticated users to exceed promo-code use limits during checkout. In Cart Service.php, promoCanBeApplied reads and checks the used counter separately from usePromo, which increments and stores it without locking, a transaction, or an atomic update. An authenticated client and an enabled limited-use promo code are required; concurrent requests can create unlimited discounted or free orders.

The record

CVE
CVE-2026-43927
Published
Jul 6, 2026
Updated
Jul 6, 2026
Vendor
FOSSBilling
Product
FOSSBilling
Classifications
CWE-367
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jul 6, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 6, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 0.8.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

FOSSBilling · FOSSBillingversion=< 0.8.0

Published CVSS scores

6.9GitHub, Inc.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

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-367Time-of-check Time-of-use (TOCTOU) Race Condition

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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