zlacker

>>rayhaa+(OP)
This vulnerability is basically the worst-case version of what people have been warning about since RSC/server actions were introduced.

The server was deserializing untrusted input from the client directly into module+export name lookups, and then invoking whatever the client asked for (without verifying that metadata.name was an own property).

    return moduleExports[metadata.name]

We can patch hasOwnProperty and tighten the deserializer, but there is deeper issue. React never really acknowledged that it was building an RPC layer. If you look at actual RPC frameworks like gPRC or even old school SOAP, they all start with schemas, explicit service definitions and a bunch of tooling to prevent boundary confusion. React went the opposite way: the API surface is whatever your bundler can see, and the endpoint is whatever the client asks for.

My guess is this won't be the last time we see security fallout from that design choice. Not because React is sloppy, but because it’s trying to solve a problem category that traditionally requires explicitness, not magic.

>>coffee+ny
The endpoint is not whatever the client asks for. It's marked specifically as exposed to the user with "use server". Of course the people who designed this recognize that this is designing an RPC system.

A similar bug could be introduced in the implementation of other RPC systems too. It's not entirely specific to this design.

(I contribute to React but not really on RSC.)

>>sophie+sN
”use server” is not required for this vulnerability to be exploitable.

>>clucki+R91
wait I'm only using React for SPA (no server rendering)

am I also vulnerable??????

>>sysgue+5l2
No, unless you run the React Server Component runtime on your server, which you wouldn't do with a SPA, you would just serve a static bundle.