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

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-2026-29772: 0.39% estimated exploitation activity in the next 30 days; percentile 32.62 (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'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: The request body…

Published by the source

24 Mar 2026, 19:29 UTC

Last modified by the source

30 Mar 2026, 14:05 UTC

Source last checked

26 Oct 2026, 12:47 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-3rmj-9m5h-8fpv

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-3rmj-9m5h-8fpv

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# Patch Next advisory brief: CVE-2026-29772

Advisory: Astro: Memory exhaustion DoS due to missing request body size limit in Server Islands
IDs: CVE-2026-29772, GHSA-3rmj-9m5h-8fpv
Record: https://patchnext.com/advisories/cve-2026-29772 (revision 2, source checked 26 Oct 2026, 12:47 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 10.0.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm @astrojs/node: affected < 10.0.0; fixed in 10.0.0

## 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-3rmj-9m5h-8fpv (OSV record GHSA-3rmj-9m5h-8fpv lists affected ranges: npm @astrojs/node >=0 <10.0.0 (fixed))
- Verified: https://github.com/advisories/GHSA-3rmj-9m5h-8fpv (GitHub-reviewed advisory GHSA-3rmj-9m5h-8fpv lists affected ranges: npm @astrojs/node >=0 <10.0.0)

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