{"id":"CVE-2026-33543","summary":"FOSSBilling: Authentication bypass allows unauthenticated administrator creation","details":"FOSSBilling is a free, open-source billing and client management system. Versions 0.7.2 and prior expose a guest API endpoint, /api/guest/staff/create, intended for initial administrator bootstrap. Due to a flawed admin-existence check, the endpoint remains usable after an administrator already exists. The flawed guard check uses is_countable() on a value that returns a Model_Admin object or null rather than a countable type, causing the expression to always evaluate as true and bypass the intended protection. As a result, an attacker can reach the unprotected endpoint to create a new administrator account and immediately authenticate, gaining a fully privileged admin session even when an admin already exists. This issue has been fixed in version 0.8.0.","aliases":["GHSA-28mh-j262-q49w"],"modified":"2026-07-15T01:49:05.579290522Z","published":"2026-06-24T21:01:16.544Z","database_specific":{"cna_assigner":"GitHub_M","cwe_ids":["CWE-288","CWE-306"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33543.json"},"references":[{"type":"WEB","url":"https://github.com/FOSSBilling/FOSSBilling/releases/tag/0.8.0"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33543.json"},{"type":"ADVISORY","url":"https://github.com/FOSSBilling/FOSSBilling/security/advisories/GHSA-28mh-j262-q49w"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-33543"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/fossbilling/fossbilling","events":[{"introduced":"0"},{"fixed":"3bd35f5b2921d8a26a403142ae0408f95e6463cc"}],"database_specific":{"extracted_events":[{"introduced":"0"},{"fixed":"0.8.0"}],"source":["AFFECTED_FIELD","REFERENCES"]}}],"versions":["0.7.2","0.7.1","0.7.0","0.6.22","0.6.21","0.6.20","0.6.19","0.6.18","0.6.17","0.6.16","0.6.15","0.6.14","0.6.13","0.6.12","0.6.11","0.6.10","0.6.9","0.6.8","0.6.7","0.6.6","0.6.5","0.6.4","0.6.3","0.6.2","0.6.1","0.6.0","0.5.5","0.5.4","0.5.3","0.5.2","0.5.1","0.5.0","0.4.3","0.4.2","0.4.1","0.4.0","0.3.0","0.2.10","0.2.9","0.2.8","0.2.7","0.2.6","0.2.5","0.2.4","0.2.3","0.2.2","0.2.1","0.2.0","0.1.1","0.1.0"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-33543.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N"}]}