DBHub is a database MCP server for Postgres, MySQL, SQL Server, Oracle, MariaDB, SQLite. Prior to version 0.22.6, setting "readonly = true" on the "execute_sql" tool does not make the connection read-only. The connectors are written to set PostgreSQL "default_transaction_read_only=on" (and open SQLite in "readOnly" mode), but that code is gated on a config value that is never populated, so it never runs. The only thing left enforcing read-only is a classifier that inspects the first keyword of each statement. Any "SELECT" that writes or has side effects through a function call passes it. With an ordinary role this allows sequence tampering; with a privileged role it allows writing arbitrary files on the server ("lo_export"), reading arbitrary host files ("pg_read_file"), and remote code execution ("dblink" + "COPY ... TO PROGRAM"). The HTTP transport is unauthenticated and binds to "0.0.0.0" by default, so this is reachable by any network caller of "/mcp". Version 0.22.6 patches the issue.