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AstroApplication

CVE-2026-54299

HIGH · 7.5 CVSS v3.1 Published 2026-06-22
Fix available
A fix is available. Upgrade to 6.4.6 or later.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Astro SSR applications with prerendered error pages (404/500 using export const prerender = true) fetch these pages at runtime over HTTP. The fetch URL is derived from request.url, which uses the incoming Host header as its origin. Since the Host header is not validated against allowedDomains before the fetch, an attacker can supply a malicious Host header to redirect internal HTTP requests to arbitrary hosts and read the responses (SSRF).

MitigationUpgrade to Astro 6.4.6 or later, which implements Host header validation against allowedDomains before using it in runtime fetches. If upgrading is not immediately possible, ensure incoming Host headers are validated at a reverse proxy or WAF level.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
AstroApplication
Affected:< 6.4.6

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Check installed Astro version
    Run `npm list astro` or examine your package.json file to find the installed astro version number
    Affected if The version is lower than 6.4.6 (e.g., 6.4.5, 6.4.0, etc.)
  2. Confirm SSR mode is enabled
    Examine your Astro configuration file (astro.config.mjs or astro.config.js) and look for an `output` setting set to 'server' or 'hybrid'. Static-only sites with output='static' are not affected
    Affected if output is set to 'server' or 'hybrid', enabling server-side rendering
  3. Identify prerendered error pages
    Check your src/pages directory for 404.astro and/or 500.astro files. Open each file and look for `export const prerender = true` at the top of the file
    Affected if A 404.astro or 500.astro file exists with `export const prerender = true` declared
  4. Verify runtime fetch behavior exists
    Review your 404.astro and 500.astro files to determine if they contain code that makes HTTP requests or fetches data at runtime using request.url or similar patterns. This is the condition that triggers use of the Host header
    Affected if The prerendered error page file contains logic that performs runtime fetches based on incoming request data

You are affected if your Astro version is below 6.4.6, SSR mode is enabled, you have prerendered error pages (404/500 with prerender=true), and those pages make runtime HTTP requests using request data derived from the Host header.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 6.4.6 or later
Fixed in 6.4.6
Interim mitigation

Upgrade to Astro 6.4.6 or later, which implements Host header validation against allowedDomains before using it in runtime fetches. If upgrading is not immediately possible, ensure incoming Host headers are validated at a reverse proxy or WAF level.

Recommended fix High confidence

6.4.6

  1. 1. Update Astro to version 6.4.6 or later by running: npm install astro@^6.4.6 or yarn add astro@^6.4.6 or pnpm add astro@^6.4.6
  2. 2. Verify the upgrade was successful by checking the installed version: npm list astro
  3. 3. Test the application to ensure the upgrade does not break existing functionality, particularly SSR error pages (/404 and /500)
Caveat Patch version upgrade within 6.x - minimal breaking change risk, but always test in staging first

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Astro Scoped from the published advisory
  • Consultation1.0 h
  • Implementation2.0 h
  • Testing2.0 h
  • Review / QA1.0 h
6.0 hours of engineering $1,040
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,664.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-54299 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data