Strawberry GraphQL is a library for creating GraphQL APIs. 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 connectioninit handshake has been completed before processing start (subscription) messages. This allows a remote attacker to skip the onwsconnect authentication hook entirely by connecting with the graphql-ws subprotocol and sending a start message directly, without ever sending connectioninit. This vulnerability is fixed in 0.312.3.