Summary An unhandled error is thrown when validating invalid connectionParams which crashes a tRPC WebSocket server. This allows any unauthenticated user to crash a tRPC 11 WebSocket server. Details Any tRPC 11 server with WebSocket enabled with a createContext method set is vulnerable. Here is an example: https://github.com/user-attachments/assets/ce1b2d32-6103-4e54-8446-51535b293b05 I have a working reproduction here if you would like to test: https://github.com/lukechilds/trpc-vuln-reproduction The connectionParams logic introduced in https://github.com/trpc/trpc/pull/5839 does not safely handle invalid connectionParams objects. During validation if the object does not match an expected shape an error will be thrown: https://github.com/trpc/trpc/blob/8cef54eaf95d8abc8484fe1d454b6620eeb57f2f/packages/server/src/unstable-core-do-not-import/http/parseConnectionParams.ts#L27-L33 This is called during WebSocket connection setup inside createCtxPromise() here: https://github.com/trpc/trpc/blob/8cef54eaf95d8abc8484fe1d454b6620eeb57f2f/packages/server/src/adapters/ws.ts#L435 createCtxPromise has handling to catch any errors and pass them up to the opts.onError handler: https://github.com/trpc/trpc/blob/8cef54eaf95d8abc8484fe1d454b6620eeb57f2f/packages/server/src/adapters/ws.ts#L144-L173 However the error handler then rethrows the error: https://github.com/trpc/trpc/blob/8cef54eaf95d8abc8484fe1d454b6620eeb57f2f/packages/server/src/adapters/ws.ts#L171 Since this is all triggered…Read More