CVE-2026-111056
CVE-2026-111056 · FOSSBilling: Unauthenticated client account enumeration via guest signup endpoint
This page contains facts from public vulnerability sources. Check the original advisory before updating.
FOSSBilling is an open source billing and client-management platform. From 0.1.0 until 0.8.7, the unauthenticated POST /api/guest/client/create endpoint reveals whether a submitted email belongs to a registered client because guest signup returns a distinct unredacted error when the submitted email already exists. The trigger is an unauthenticated request to POST /api/guest/client/create with a target email address. An attacker can compare the guest-signup response for a target email to determine whether the email belongs to an existing FOSSBilling client. Box\Mod\Client\Api\Guest::create returns the error after Client\Service::clientAlreadyExists finds a matching record, and the API response exposes that exception message without redaction. This issue is fixed in version 0.8.7.
CVSS 6.9 · Medium · EPSS 0.3%
- Published
- Updated
Affected products and versions
fossbilling
- Versions
- >= 0.1.0, < 0.8.7: Affected
No fix published
Original sources
- https://github.com/FOSSBilling/FOSSBilling/security/advisories/GHSA-x4mh-g4pc-wfc5
- https://github.com/FOSSBilling/FOSSBilling/pull/4234
- https://github.com/FOSSBilling/FOSSBilling/commit/19f41ff0a45874c7362b7732c8f68db84bc59c55
- https://github.com/FOSSBilling/FOSSBilling/releases/tag/0.8.7
- https://nvd.nist.gov/vuln/detail/CVE-2026-111056