Astro has memory exhaustion DoS due to missing request body size limit in Server Actions

Exploitation

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

CVSS

5.9 · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS

• CVE-2026-27729: 0.48% estimated exploitation activity in the next 30 days; percentile 41.63 (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 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 <details Setup Create a new Astro project with the following files: package.json: astro.config.mjs: src/actions/index.ts:…

Published by the source

25 Feb 2026, 22:33 UTC

Last modified by the source

25 Feb 2026, 22:56 UTC

Source last checked

26 Oct 2026, 12:42 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-jm64-8m5q-4qh8

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-jm64-8m5q-4qh8

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# Patch Next advisory brief: CVE-2026-27729

Advisory: Astro has memory exhaustion DoS due to missing request body size limit in Server Actions
IDs: CVE-2026-27729, GHSA-jm64-8m5q-4qh8
Record: https://patchnext.com/advisories/cve-2026-27729 (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 5.9)
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-jm64-8m5q-4qh8 (OSV record GHSA-jm64-8m5q-4qh8 lists affected ranges: npm @astrojs/node >=9.0.0 <9.5.4 (fixed))
- Verified: https://github.com/advisories/GHSA-jm64-8m5q-4qh8 (GitHub-reviewed advisory GHSA-jm64-8m5q-4qh8 lists affected ranges: npm @astrojs/node >=9.0.0 <9.5.4)

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