Nebula Mesh: Web UI lacks ownership checks, enabling cross-operator access to hosts and networks (read, block, delete)

The web UI (/ui/*) does not apply the per-operator CA scoping the JSON API received for GHSA-598g-h2vc-h5vg. Any authenticated non-admin operator (for example, one created via self-registration or OIDC) can access resources belonging to other operators.

A non-admin operator can:

• Block or delete any other operator's host. POST /ui/hosts/{id}/block and DELETE /ui/hosts/{id} act on the URL id with no ownership check, so a non-admin can block (revoking the host's certificate via the blocklist) or delete any host in the deployment — a cross-operator denial of service.
• Read every operator's hosts and networks. The dashboard, /ui/hosts, the host detail page, /ui/networks (including the create-form error re-render), and the /ui/events stream all return data across all operators, exposing host names, Nebula IPs, public IPs, certificate fingerprints and expiry, and network names and CIDRs.

This is the same cross-operator class as GHSA-598g; that remediation covered the JSON API but not the web read/mutation surface. The host create/edit/mobile-bundle/network-create paths and all CA-management routes were already correctly scoped.

Affected handlers (internal/web): handleHostDetail, handleHostBlock, handleHostDelete, handleDashboard, handlePartialStats, handleHosts, handleNetworks, renderNetworksError, handleHostEvents.

Exposure requires at least one non-admin operator to exist (self-registration enabled, OIDC, or an admin-created user). A single-admin deployment with no additional operators is not affected.

A complete candidate fix with regression tests is ready in a private repository shared with the maintainer (ak2k/nebula-mesh-ghsa-web, PR #1): scope these handlers to the session operator's owned CAs (admins keep the full view), mirroring the API's ownership checks.