# 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.

- **Severity:** Medium 5.9 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 24 Mar 2026
- **Updated:** 24 Mar 2026
- **Also known as:** GHSA-3rmj-9m5h-8fpv

## 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 (Allocation of Resources Without Limits or Throttling)

## Which versions are affected by CVE-2026-29772?

2 open source packages ship an affected version, including @astrojs/node. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `@astrojs/node` | npm | All versions | 10.0.0 |
| `@astrojs/node` | npm | All versions | 10.0.0 |

Products: Astro \@Astrojs\/Node.

## How do I fix CVE-2026-29772?

Upgrade @astrojs/node to 10.0.0 or later.

## 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

- [CVE-2026-25545](https://insights.sbomify.com/CVE-2026-25545/): Astro has Full-Read SSRF in error rendering via Host: header injection (medium 6.9)
- [CVE-2026-27829](https://insights.sbomify.com/CVE-2026-27829/): Astro is vulnerable to SSRF due to missing allowlist enforcement in remote image inferSize (medium 6.5)
- [CVE-2026-27729](https://insights.sbomify.com/CVE-2026-27729/): Astro has memory exhaustion DoS due to missing request body size limit in Server Actions (medium 5.9)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-29772 and fix it if it is affected.

What it is: 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.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-29772 exists.

Affected packages and fixed versions:
- @astrojs/node (npm): affected all versions; fixed in 10.0.0
- @astrojs/node (npm): affected all versions; fixed in 10.0.0

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-29772/ (Markdown: https://insights.sbomify.com/CVE-2026-29772/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-29772
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-29772
- OSV: https://osv.dev/vulnerability/CVE-2026-29772

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-29772/
Summaries are generated and may contain mistakes; the official description above is the record.