GHSA-9m65-766c-r333: TanStack Start - Server Core: Inbound server-function request deserialization could invoke a sibling client-referenced server function

A type-confusion bug in seroval ≤ 1.5.2 (upstream advisory) allowed a crafted JSON body sent to one TanStack Start server function to trigger invocation of a different client-referenced server function as a side effect of deserializing the request payload.

This is not an authentication bypass and not remote code execution. The mechanism only invokes server functions that the same client could already reach directly via /_serverFn/, and the target function’s full middleware chain — including any user-supplied authentication, authorization, and inputValidator — runs as it would on a direct call.