{"id":"CVE-2026-111056","url":"https://www.cyber-defence.io/tools/cve/CVE-2026-111056","generatedAt":"2026-10-28T01:12:13.431Z","title":"An attacker can compare the guest-signup response for a target email to determine whether the email belongs to an existing FOSSBilling client.","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.","published":"2026-10-19T16:17:04.000Z","lastModified":"2026-10-22T04:17:30.000Z","status":"Deferred","sourceIdentifier":"security-advisories@github.com","cvss":{"version":"4.0","score":6.9,"severity":"MEDIUM","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/M"},"cwe":["CWE-200","CWE-204","CWE-307"],"affected":[],"epss":{"score":0.00285,"percentile":0.20881,"date":"2026-10-26","history":[{"date":"2026-10-20","score":0.00285,"percentile":0.19818}]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"low","text":"Lower severity and a low EPSS score (0.29%). Track it; it rarely justifies an emergency change on its own."},"changes":[{"kind":"new","label":"New CVE","at":"2026-10-19T16:17:04.000Z","detail":{"score":"6.9","severity":"MEDIUM","publishedAt":"2026-10-19T16:17:03.657Z"},"summary":"New CVE, medium severity (CVSS 6.9)."}],"references":[{"url":"https://github.com/FOSSBilling/FOSSBilling/commit/19f41ff0a45874c7362b7732c8f68db84bc59c55","source":"security-advisories@github.com"},{"url":"https://github.com/FOSSBilling/FOSSBilling/pull/4234","source":"security-advisories@github.com"},{"url":"https://github.com/FOSSBilling/FOSSBilling/releases/tag/0.8.7","source":"security-advisories@github.com"},{"url":"https://github.com/FOSSBilling/FOSSBilling/security/advisories/GHSA-x4mh-g4pc-wfc5","source":"security-advisories@github.com"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-111056","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}