CVE-2026-100718

Froxlor through 2.3.10 does not enforce the mail.allow_external_domains policy in the EmailSender.add API command. When an administrator has enabled the allowed-sender feature but disabled external allowed-sender domains (mail.enable_allow_sender = 1, mail.allow_external_domains = 0), an authenticated customer with API access can still use EmailSender.add to register an arbitrary external sender address for their mailbox, which is stored despite the policy. This creates a bypass between the UI/administrator configuration and the API, and — where the generated mail configuration consumes the allowed-sender table — allows a customer to authorize sender identities outside their hosted domains, facilitating sender spoofing. Fixed in 2.3.12.

• https://github.com/froxlor/froxlor/security/advisories/GHSA-m9j6-9856-68xf
• https://www.vulncheck.com/advisories/froxlor-before-2.3.12-authentication-bypass-via-emailsender-add