{"id":"CVE-2026-111056","published":"2026-10-19T16:17:03.657","lastModified":"2026-10-19T16:17:03.773","description":"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.","cvssScore":null,"cvssSeverity":null,"cvssVector":null,"cwes":["CWE-200","CWE-204","CWE-307"],"vendors":[],"products":[],"references":[{"url":"https://github.com/FOSSBilling/FOSSBilling/commit/19f41ff0a45874c7362b7732c8f68db84bc59c55","tags":[]},{"url":"https://github.com/FOSSBilling/FOSSBilling/pull/4234","tags":[]},{"url":"https://github.com/FOSSBilling/FOSSBilling/releases/tag/0.8.7","tags":[]},{"url":"https://github.com/FOSSBilling/FOSSBilling/security/advisories/GHSA-x4mh-g4pc-wfc5","tags":[]}],"exploitRefs":[{"url":"https://github.com/FOSSBilling/FOSSBilling/commit/19f41ff0a45874c7362b7732c8f68db84bc59c55","tags":[]},{"url":"https://github.com/FOSSBilling/FOSSBilling/pull/4234","tags":[]},{"url":"https://github.com/FOSSBilling/FOSSBilling/releases/tag/0.8.7","tags":[]},{"url":"https://github.com/FOSSBilling/FOSSBilling/security/advisories/GHSA-x4mh-g4pc-wfc5","tags":[]}],"hasPoc":true,"ai":null}