CVE-2026-111056

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.

• CWE-200
• CWE-204
• CWE-307

• https://github.com/FOSSBilling/FOSSBilling/commit/19f41ff0a45874c7362b7732c8f68db84bc59c55
• https://github.com/FOSSBilling/FOSSBilling/pull/4234
• https://github.com/FOSSBilling/FOSSBilling/releases/tag/0.8.7
• https://github.com/FOSSBilling/FOSSBilling/security/advisories/GHSA-x4mh-g4pc-wfc5

Published

Oct 19, 2026

Last Modified

Oct 22, 2026

Status

Deferred

• How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
• Autonomous PentestingAI agents that find and validate exploitable vulnerabilities like this one across your applications.
• PR ReviewsPentest every pull request so vulnerable code is caught before it ships to production.
• AI Penetration TestingHow AI-driven penetration testing continuously covers your attack surface.

• CVE-2026-111045CLI Bridge provides filesystem access within a workspace roo…7.5
• CVE-2026-111046FOSSBilling is an open source billing and client-management …2.3
• CVE-2026-111048FOSSBilling is an open source billing and client-management …8.4
• CVE-2026-11105Insufficient validation of untrusted input in WebUI in Googl…6.5
• CVE-2026-111053FOSSBilling is an open source billing and client-management …6.9
• CVE-2026-111054Rejected reason: ** REJECT ** DO NOT USE THIS CANDIDATE NUMB…
• CVE-2026-111057Mercury is a Python framework for sharing Jupyter notebooks …10
• CVE-2026-111058Mercury is a Python framework for sharing Jupyter notebooks …9.8
• CVE-2026-111059Mercury is a Python framework for sharing Jupyter notebooks …6.1
• CVE-2026-11106Inappropriate implementation in Media in Google Chrome prior…6.5
• CVE-2026-111061russh is a Rust SSH client and server library that includes …4.3
• CVE-2026-111063AIOHTTP is an asynchronous HTTP client/server framework for …6.3