withastro up to 9.5.3 allocation of resources

Summaryinfo

A vulnerability, which was classified as problematic, has been found in withastro astro up to 9.5.3. This affects an unknown function. This manipulation causes allocation of resources. The identification of this vulnerability is CVE-2026-27729. It is possible to initiate the attack remotely. There is no exploit available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability classified as problematic was found in withastro astro up to 9.5.3. Affected by this vulnerability is an unknown functionality. The manipulation with an unknown input leads to a allocation of resources vulnerability. The CWE definition for the vulnerability is 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. As an impact it is known to affect availability. The summary by CVE is:

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.

The advisory is shared at github.com. This vulnerability is known as CVE-2026-27729 since 02/23/2026. The exploitation appears to be difficult. The attack can be launched remotely. The exploitation doesn't need any form of authentication. Neither technical details nor an exploit are publicly available. MITRE ATT&CK project uses the attack technique T1499 for this issue.

Upgrading to version 9.5.4 eliminates this vulnerability. The upgrade is hosted for download at github.com. Applying the patch 522f880b07a4ea7d69a19b5507fb53a5ed6c87f8 is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

Vendor

• withastro

Name

• astro

Version

• 9.5.0
• 9.5.1
• 9.5.2
• 9.5.3

License

• open-source

Website

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

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