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.
PUBLISHED5.2CWE-20CWE-918
Astro: Host-header full-read SSRF in core prerendered error-page fetch (prerenderedErrorPageFetch default + unvalidated createRequestFromNodeRequest URL)
Problem type
Affected products
withastro
astro
< 6.4.6 - AFFECTED
References
GitHub Security Advisories
GHSA-2pvr-wf23-7pc7
Astro: Host header SSRF in prerendered error page fetch
https://github.com/advisories/GHSA-2pvr-wf23-7pc7Summary
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 500 page
- Use
createRequestFromNodeRequestfromastro/app/nodewithapp.render()without overridingprerenderedErrorPageFetch— 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
JSON source
https://cveawg.mitre.org/api/cve/CVE-2026-54299Click to expand
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"assignerShortName": "GitHub_M",
"dateUpdated": "2026-06-22T17:33:53.235Z",
"dateReserved": "2026-06-12T17:46:37.293Z",
"datePublished": "2026-06-22T17:33:53.235Z",
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"title": "Astro: Host-header full-read SSRF in core prerendered error-page fetch (prerenderedErrorPageFetch default + unvalidated createRequestFromNodeRequest URL)",
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"value": "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."
}
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"affected": [
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"problemTypes": [
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"url": "https://github.com/withastro/astro/security/advisories/GHSA-2pvr-wf23-7pc7",
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"attackVector": "NETWORK",
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"privilegesRequired": "NONE",
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"scope": "CHANGED",
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