Astro: Host header SSRF in prerendered error page fetch

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

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

EPSS

• CVE-2026-54299: 0.33% estimated exploitation activity in the next 30 days; percentile 26.54 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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…

Published by the source

16 Jun 2026, 14:38 UTC

Last modified by the source

12 Aug 2026, 20:45 UTC

Source last checked

26 Oct 2026, 13:01 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-2pvr-wf23-7pc7

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-2pvr-wf23-7pc7

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# Patch Next advisory brief: CVE-2026-54299

Advisory: Astro: Host header SSRF in prerendered error page fetch
IDs: CVE-2026-54299, GHSA-2pvr-wf23-7pc7
Record: https://patchnext.com/advisories/cve-2026-54299 (revision 2, source checked 26 Oct 2026, 13:01 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: astro 6.4.6. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm astro: affected < 6.4.6; fixed in 6.4.6

## Suggested inspection (read-only)
- `npm ls astro --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on astro.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-2pvr-wf23-7pc7 (OSV record GHSA-2pvr-wf23-7pc7 lists affected ranges: npm astro >=0 <6.4.6 (fixed))
- Verified: https://github.com/advisories/GHSA-2pvr-wf23-7pc7 (GitHub-reviewed advisory GHSA-2pvr-wf23-7pc7 lists affected ranges: npm astro >=0 <6.4.6)

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