Strawberry up until version 0.312.3 is vulnerable to an authentication bypass on WebSocket subscription endpoints. The legacy graphql-ws subprotocol handler does not verify that a connection_init handshake has been completed before processing start (subscription) messages. This allows a remote attacker to skip the on_ws_connect authentication hook entirely by connecting with the graphql-ws subprotocol and sending a start message directly, without ever sending connection_init.

The graphql-transport-ws subprotocol handler is not affected, as it correctly gates subscription operations on a connection_acknowledged flag. However, both subprotocols are enabled by default in all framework integrations that support websockets, and the subprotocol is selected by the client via the Sec-WebSocket-Protocol header.

Any application relying on on_ws_connect for authentication or authorization is affected.

Mitigation: Upgrade to the patched version, or explicitly disable the legacy graphql-ws subprotocol by setting subscription_protocols=[GRAPHQL_TRANSPORT_WS_PROTOCOL] on your GraphQL view/router.