CVE-2026-27729

The record

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.

Affected packages

Related vulnerabilities

• GHSA-jm64-8m5q-4qh8 Astro has memory exhaustion DoS due to missing request body size limit in Server Actions Same vulnerability
• CVE-2026-41322 @astrojs/node allows Astro to deploy your SSR site to Node targets. Also affects @astrojs/node
• GHSA-c57f-mm3j-27q9 Astro: Cache Poisoning due to incorrect error handling when if-match header is malformed Also affects @astrojs/node
• GHSA-3rmj-9m5h-8fpv Astro: Memory exhaustion DoS due to missing request body size limit in Server Islands Also affects @astrojs/node
• CVE-2026-29772 Astro is a web framework. Also affects @astrojs/node
• CVE-2026-27829 Astro is a web framework. Also affects @astrojs/node
• GHSA-cj9f-h6r6-4cx2 Astro is vulnerable to SSRF due to missing allowlist enforcement in remote image inferSize Also affects @astrojs/node
• CVE-2026-25545 Astro is a web framework. Also affects @astrojs/node