RabbitMQ is a messaging and streaming broker. Prior to versions 3.13.15, 4.0.20, 4.1.11, 4.2.6, and 4.3.0, add vhost/2 calls rabbit data coercion:atomize keys/1 (the unsafe variant using binary to atom) on the vhost metadata map. The 20 MB management body limit fits ~1M+ short keys. Admin-only. An administrator importing a crafted definitions file can crash the node in a single request: a vhosts entry with ~1M unique metadata keys exhausts the atom table during import. Preconditions include administrator tag. This issue is fixed in versions 3.13.15, 4.0.20, 4.1.11, 4.2.6, and 4.3.0.