DBHub HTTP transport DNS rebinding allows unauthenticated browser-origin SQL execution

Summary

DBHub is a database MCP server for Postgres, MySQL, SQL Server, Oracle, MariaDB, SQLite. Versions prior to 0.22.5 expose an unauthenticated HTTP MCP endpoint when started with the documented HTTP transport mode, for example `--transport http --port 8080`. The HTTP server attempts to protect browser-origin access by checking whether the `Origin` hostname equals the `Host` hostname, then reflecting the validated `Origin` into `Access-Control-Allow-Origin`. This does not stop DNS rebinding. After an attacker-controlled hostname rebinds to a victim-accessible DBHub HTTP server, both `Origin` and `Host` can contain the attacker-controlled hostname, so DBHub accepts the request and dispatches MCP tool calls. As a result, a malicious website can deterministically invoke DBHub MCP tools from the victim's browser without prompt injection or model involvement. With the default demo configuration this can read and write the demo SQLite database; with a real configured database, the same primitive can read, enumerate, and potentially write database contents depending on DBHub's configured tool permissions and database credentials. Version 0.22.5 fixes the issue.