{"id":"CVE-2026-111056","aliases":["EUVD-2026-104418","GHSA-x4mh-g4pc-wfc5"],"status":"published","title":"FOSSBilling: Unauthenticated client account enumeration via guest signup endpoint","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.","severity":{"version":"4.0","score":6.9,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N","level":"medium","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-12","score":0.00285,"percentile":0.21333,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":false},"cwes":["CWE-200","CWE-204","CWE-307"],"published":"2026-10-19T16:00:57Z","modified":"2026-10-28T02:31:12Z","products":[{"vendor":"fossbilling","product":"fossbilling"}],"references":[{"url":"https://github.com/FOSSBilling/FOSSBilling/security/advisories/GHSA-x4mh-g4pc-wfc5","tags":["x_refsource_CONFIRM","advisory"]},{"url":"https://github.com/FOSSBilling/FOSSBilling/pull/4234","tags":["x_refsource_MISC","fix"]},{"url":"https://github.com/FOSSBilling/FOSSBilling/commit/19f41ff0a45874c7362b7732c8f68db84bc59c55","tags":["x_refsource_MISC","fix"]},{"url":"https://github.com/FOSSBilling/FOSSBilling/releases/tag/0.8.7","tags":["x_refsource_MISC","web"]},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/111xxx/CVE-2026-111056.json","tags":["advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-111056","tags":["advisory"]}],"sources":{"cve":[{"id":"CVE-2026-111056","title":"FOSSBilling: Unauthenticated client account enumeration via guest signup endpoint","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.","status":"published","published":"2026-10-19T16:00:57.576Z","modified":"2026-10-22T03:02:43.261Z","cvss":[{"version":"4.0","score":6.9,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N","level":"medium","assessor":"cna"}],"cwes":["CWE-200","CWE-204","CWE-307"],"updated_at":"2026-11-02T14:20:15.34316Z"}],"euvd":[{"id":"EUVD-2026-104418","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.","status":"published","published":"2026-10-19T16:00:57Z","modified":"2026-10-22T03:02:43Z","cvss":[{"version":"4.0","score":6.9,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N","level":"medium"}],"updated_at":"2026-11-02T16:59:35.538537Z"}],"nvd":[{"id":"CVE-2026-111056","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.","status":"published","published":"2026-10-19T16:17:03.657Z","modified":"2026-10-22T04:17:29.873Z","cvss":[{"version":"4.0","score":6.9,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/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","level":"medium","assessor":"secondary"}],"cwes":["CWE-200","CWE-204","CWE-307"],"updated_at":"2026-11-02T14:13:00.83844Z"}],"osv":[{"id":"CVE-2026-111056","title":"FOSSBilling: Unauthenticated client account enumeration via guest signup endpoint","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.","status":"published","published":"2026-10-19T16:00:57.576Z","modified":"2026-10-28T02:31:12.68654039Z","cvss":[{"version":"4.0","score":6.9,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N","level":"medium"}],"cwes":["CWE-200","CWE-204","CWE-307"],"updated_at":"2026-11-02T15:44:55.61515Z"}]}}