GHSA-2PVR-WF23-7PC7 Astro: Host header SSRF in prerendered error page fetch

Summary Astro SSR apps with prerendered error pages /404 or /500 using export const prerender = true fetch those pages over HTTP at runtime when an error occurs. The URL for this fetch is derived from request.url, which in turn gets its origin from the incoming Host header. When the Host header i...