Astro: Host header SSRF in prerendered error page fetch
CVE-2026-54299 High
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 is not validated against allowedDomains, an attacker can point the fetch at an arbitrary host and read the response.
Who is affected
This affects SSR deployments that:
- Have a prerendered 404 or…
- Affected component
- astro
- Fixed in
- 6.4.6