Astro is vulnerable to SSRF due to missing allowlist enforcement in remote image inferSize

Exploitation

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

CVSS

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

EPSS

• CVE-2026-27829: 0.32% estimated exploitation activity in the next 30 days; percentile 25.02 (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 A bug in Astro's image pipeline allows bypassing image.domains / image.remotePatterns restrictions, enabling the server to fetch content from unauthorized remote hosts. Details Astro provides an inferSize option that fetches remote images at render time to determine their dimensions. Remote image fetches are intended to be restricted to domains the site developer has manually authorized (using the image.domains or image.remotePatterns options). However, when inferSize is used, no domain validation is performed — the image is fetched from any host regardless of the configured restrictions. An attacker who can influence the image URL (e.g., via CMS content or user-supplied data) can cause the server to fetch from arbitrary hosts. PoC <details Setup Create a new Astro project with the following files: package.json: astro.config.mjs — only localhost:9000 is authorized: internal-service.mjs — simulates an internal service on a non-allowlisted host (127.0.0.1:8888):…

Published by the source

25 Feb 2026, 18:11 UTC

Last modified by the source

28 Feb 2026, 05:13 UTC

Source last checked

26 Oct 2026, 12:42 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-cj9f-h6r6-4cx2

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-cj9f-h6r6-4cx2

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2026-27829

Advisory: Astro is vulnerable to SSRF due to missing allowlist enforcement in remote image inferSize
IDs: CVE-2026-27829, GHSA-cj9f-h6r6-4cx2
Record: https://patchnext.com/advisories/cve-2026-27829 (revision 2, source checked 26 Oct 2026, 12:42 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: @astrojs/node 9.5.4. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm @astrojs/node: affected >= 9.0.0, < 9.5.4; fixed in 9.5.4

## Suggested inspection (read-only)
- `npm ls @astrojs/node --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 @astrojs/node.
- 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-cj9f-h6r6-4cx2 (OSV record GHSA-cj9f-h6r6-4cx2 lists affected ranges: npm @astrojs/node >=9.0.0 <9.5.4 (fixed))
- Verified: https://github.com/advisories/GHSA-cj9f-h6r6-4cx2 (GitHub-reviewed advisory GHSA-cj9f-h6r6-4cx2 lists affected ranges: npm @astrojs/node >=9.0.0 <9.5.4)

Commands are suggestions: review each one before running it.