Summaryinfo

A vulnerability was found in withastro astro up to 9.x. It has been declared as problematic. This issue affects the function JSON.parse of the file /_server-islands/ of the component POST Handler. Such manipulation leads to allocation of resources. This vulnerability is uniquely identified as CVE-2026-29772. The attack can be launched remotely. No exploit exists. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability was found in withastro astro up to 9.x. It has been rated as problematic. Affected by this issue is the function JSON.parse of the file /_server-islands/ of the component POST Handler. The manipulation with an unknown input leads to a allocation of resources vulnerability. Using CWE to declare the problem leads to CWE-770. The product allocates a reusable resource or group of resources on behalf of an actor without imposing any restrictions on the size or number of resources that can be allocated, in violation of the intended security policy for that actor. Impacted is availability. CVE summarizes:

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.

The advisory is available at github.com. This vulnerability is handled as CVE-2026-29772 since 03/04/2026. The exploitation is known to be difficult. The attack may be launched remotely. No form of authentication is required for exploitation. Technical details are known, but there is no available exploit. This vulnerability is assigned to T1499 by the MITRE ATT&CK project.

Upgrading to version 10.0.0 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-14962). If you want to get best quality of vulnerability data, you may have to visit VulDB.

Productinfo

Vendor

• withastro

Name

• astro

Version

• 9.x

Website

• Product: https://github.com/withastro/astro/

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