Astro: Host-header full-read SSRF in core prerendered error-page fetch (prerenderedErrorPageFetch default + unvalidated createRequestFromNodeRequest URL)

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

Astro is a web framework. Prior to 6.4.6, 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. This vulnerability is fixed in 6.4.6.

Source published

22 Jun 2026 17:33:53 UTC

Source modified

23 Jun 2026 15:06:45 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

CVE Program Terms of Use

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CVSS 3.1 · 7.5 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:L/A:N

Astro is a web framework. Prior to 6.4.6, 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. This vulnerability is fixed in 6.4.6.

Source published

Jun 22, 2026, 5:33:53 PM (timezone not stated)

Source modified

Jun 23, 2026, 3:06:45 PM (timezone not stated)

Observed here

7 Nov 2026 12:29:13 UTC

Source terms

ENISA EUVD · source terms and attribution apply

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EUVD CVSS 3.1 · 7.5 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:L/A:N

Astro is a web framework. Prior to 6.4.6, 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. This vulnerability is fixed in 6.4.6.

Source published

22 Jun 2026 19:17:21 UTC

Source modified

25 Oct 2026 23:10:00 UTC

Observed here

27 Oct 2026 14:13:32 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · [email protected] · Secondary · 7.5 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:L/A:N

CVSS 3.1 · [email protected] · Primary · 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

## 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: 1. Have a prerendered 404 or 500 page 2. Use `createRequestFromNodeRequest` from `astro/app/node` with `app.render()` **without** overriding `prerenderedErrorPageFetch` — this includes custom servers built on the public API and third-party adapters **Not affected:** - `@astrojs/node` >= 9.5.4 (reads error pages from disk) - `@astrojs/cloudflare` (uses the ASSETS binding) - The dev server (renders error pages in-process) ## How it works `createRequestFromNodeRequest` builds `request.url` from the raw `Host` / `:authority` header. The `allowedDomains` option is accepted but only gates `X-Forwarded-For` — it does not constrain the URL origin. (The public `createRequest` does fall back to `localhost` for unvalidated hosts; this internal builder did not.) When `app.render()` encounters a 404 or 500 with a prerendered error route, `default-handler.ts` constructs the error page URL using the origin from `request.url` and fetches it via `prerenderedErrorPageFetch`, which defaults to global `fetch`. The response body is served to the client. An attacker sends a request with `Host: attacker-host:port`, triggers an error (e.g., requesting a nonexistent path for a 404), and receives the response from the attacker-controlled host reflected back. ## Remediation The error page fetch origin is now validated against `allowedDomains` before use. When the host is validated, the original origin is preserved. Otherwise, it falls back to `localhost`. The fetch is also wrapped in a try/catch so that connection failures degrade gracefully to a plain error response. ## Credit 5ud0 / Tarmo Technologies

Source published

16 Jun 2026 14:38:06 UTC

Source modified

12 Aug 2026 20:45:07 UTC

Observed here

24 Oct 2026 13:17:17 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V3 · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:L/A:N

Publisher rating · HIGH