CalDAV is an open protocol for synchronizing calendar data between a server and client devices such as phones, desktops, and web apps. It builds on WebDAV and HTTP so users can create, update, and fetch events, invitations, and schedules from a central calendar service.
In cyber security, CalDAV matters because it often runs inside account management or collaboration systems that handle trusted user data. If a CalDAV service has an authentication, authorization, or parsing flaw, an attacker may be able to read private calendar data, modify events, or use the service as a stepping stone to broader compromise. In shared hosting and enterprise platforms, defenders watch CalDAV endpoints for unusual requests, privilege-boundary failures, and unexpected access between accounts. Hardening usually includes strong authentication, least-privilege service accounts, patching, and logging for abnormal calendar operations.