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Missing AuthenticationWeakness · CWE-306

CVE-2026-42341

CRITICAL · 9.2 CVSS v4.0 Published 2026-07-06
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click 7 weeks old

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
FOSSBilling is a free, open-source billing and client management system. Versions 0.6.0 through 0.7.2 have an unauthenticated payment bypass vulnerability in FOSSBilling's IPN callback endpoint. When the Custom payment adapter is enabled, an attacker can mark any unpaid invoice as paid and credit the associated client account without making an actual payment, by sending a single crafted HTTP request. Version 0.8.0 patches the issue. Some workarounds are available. Disable the Custom payment gateway if not actively needed and/or restrict access to `/ipn.php` at the web server level (e.g., via IP allowlisting), noting that this may interfere with legitimate payment callback processing.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

FOSSBilling versions 0.6.0-0.7.2 contain an unauthenticated payment bypass vulnerability in the IPN callback endpoint when the Custom payment adapter is enabled. Attackers can send a single crafted HTTP request to mark any unpaid invoice as paid and credit the client account without making any actual payment.

MitigationUpgrade to FOSSBilling version 0.8.0 or later. If upgrade is not immediately possible, disable the Custom payment gateway if not actively needed and/or restrict access to /ipn.php via IP allowlisting at the web server level.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
Authentication
X
User interaction
None
Scope
X

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:H/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify FOSSBilling installation and version
    Locate the FOSSBilling installation directory and check the version file (commonly found in src/VERSION, composer.json, or configuration files). Compare the installed version number against the affected range 0.6.0-0.7.2.
    Affected if Installed version falls within 0.6.0 through 0.7.2 inclusive.
  2. Verify Custom payment adapter is enabled
    Access the FOSSBilling admin panel and navigate to Settings > Payment Gateways, or inspect the payment configuration files in the installation. Look for the 'Custom' payment adapter and confirm whether it is enabled or activated.
    Affected if The Custom payment gateway/adaptor is enabled or active in the payment settings.
  3. Confirm IPN callback endpoint is accessible
    Check for the presence of ipn.php in the web root directory. Verify that the endpoint is reachable externally without authentication (no login required to access it).
    Affected if The file ipn.php exists and is accessible without authentication on the web server.
  4. Check for suspicious payment records
    Review the invoice payment history in the admin panel or database for any invoices marked as paid that show no corresponding payment gateway transaction record, especially if the Custom payment method was used.
    Affected if There are invoices marked as paid via the Custom payment gateway without legitimate transaction records.

You are affected if FOSSBilling version 0.6.0-0.7.2 is installed AND the Custom payment adapter is enabled, allowing unauthenticated access to the IPN callback endpoint.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade to FOSSBilling version 0.8.0 or later. If upgrade is not immediately possible, disable the Custom payment gateway if not actively needed and/or restrict access to /ipn.php via IP allowlisting at the web server level.

Recommended fix High confidence

0.8.0

  1. Upgrade FOSSBilling to version 0.8.0 which contains the patch for this vulnerability
  2. If immediate upgrade is not possible, disable the Custom payment gateway from the admin panel if it is not actively in use
  3. As an additional mitigation, configure web server access controls to restrict /ipn.php to known IP addresses only (IP allowlisting)
Caveat Review FOSSBilling 0.8.0 release notes for any breaking changes between 0.7.x and 0.8.0 before upgrading

Generated from the published advisory — verify against the referenced sources before acting.

Have this fixed Scoped from the published advisory
  • Consultation4.0 h
  • Implementation4.0 h
  • Testing8.0 h
  • Review / QA4.0 h
20.0 hours of engineering $3,440
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-42341 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data