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5.9

Astro Node adapter can crash from oversized POST request

CVE-2026-27729 · published 8 months ago
Summary

The Astro web framework (versions 9.0.0 through 9.5.3) lets anyone send a very large POST to a server‑action endpoint, and the server reads the entire body into memory with no size limit. This can fill up memory, stop the site, and cause a restart loop in container setups. Upgrade to version 9.5.4 or later, or add your own request‑size checks, to prevent the crash.

What to do
  • Update astrojs node to version 9.5.4.
  • Update astro \@astrojs\/node to version 9.5.4 or later.
Affected software
Ecosystem VendorProductAffected versions
npm astrojs node >= 9.0.0, < 9.5.4
Fix: upgrade to 9.5.4
– astro \@astrojs\/node >= 9.0.0, < 9.5.4
cpe:2.3:a:astro:\@astrojs\/node:*:*:*:*:*:node.js:*:*
Original advisory text
Astro has memory exhaustion DoS due to missing request body size limit in Server Actions
Astro is a web framework. In versions 9.0.0 through 9.5.3, 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. 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. The vulnerability 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. Version 9.5.4 contains a fix.
References
Fix within
Internet-facing 14 days
Internal 60 days
  • Not known to be exploited
  • Can be exploited automatically (estimated)
  • Gives an attacker partial control (estimated)
Severity
5.9 Medium
Exploitation
<1% chance of attack within 30 days
Type
CWE-770Allocation of Resources Without Limits
Timeline
Published24 Feb 2026
Updated4 Nov 2026
First seen6 Mar 2026
Sources
CVE-2026-27729 · NVD
GHSA-jm64-8m5q-4qh8 · GHSA
CVE-2026-27729 · OSV
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