CVE-2026-29772 Astro: Memory exhaustion DoS due to missing request body size limit in Server Islands
Unauthenticated attackers can crash Astro SSR servers by sending large JSON payloads to Server Islands endpoints, causing memory exhaustion.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-29772?
CVE-2026-29772 is a medium-severity denial of service vulnerability in withastro astro, published on 24 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Astro is a web framework. Prior to version 10.0.0, 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. This issue has been patched in version 10.0.0.
Weakness: CWE-770
Which versions are affected by CVE-2026-29772?
2 open source packages ship an affected version, including @astrojs/node. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
@astrojs/node npm | All versions | 10.0.0 |
@astrojs/node npm | All versions | 10.0.0 |
Products include Astro \@Astrojs\/Node.
How do I fix CVE-2026-29772?
Upgrade @astrojs/node to 10.0.0 or later.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-29772 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-29772 exists.
Other vulnerabilities in withastro astro
Sources
Also known as GHSA-3rmj-9m5h-8fpv.