withastro up to 9.5.3 Image Parser server-side request forgery

Summaryinfo

A vulnerability classified as critical has been found in withastro astro up to 9.5.3. This vulnerability affects unknown code of the component Image Parser. Performing a manipulation results in server-side request forgery. This vulnerability is known as CVE-2026-27829. Remote exploitation of the attack is possible. No exploit is available. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability was found in withastro astro up to 9.5.3. It has been classified as critical. This affects some unknown processing of the component Image Parser. The manipulation with an unknown input leads to a server-side request forgery vulnerability. CWE is classifying the issue as CWE-918. The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination. This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE is:

Astro is a web framework. In versions 9.0.0 through 9.5.3, a bug in Astro's image pipeline allows bypassing `image.domains` / `image.remotePatterns` restrictions, enabling the server to fetch content from unauthorized remote hosts. Astro provides an `inferSize` option that fetches remote images at render time to determine their dimensions. Remote image fetches are intended to be restricted to domains the site developer has manually authorized (using the `image.domains` or `image.remotePatterns` options). However, when `inferSize` is used, no domain validation is performed — the image is fetched from any host regardless of the configured restrictions. An attacker who can influence the image URL (e.g., via CMS content or user-supplied data) can cause the server to fetch from arbitrary hosts. This allows bypassing `image.domains` / `image.remotePatterns` restrictions to make server-side requests to unauthorized hosts. This includes the risk of server-side request forgery (SSRF) against internal network services and cloud metadata endpoints. Version 9.5.4 fixes the issue.

It is possible to read the advisory at github.com. This vulnerability is uniquely identified as CVE-2026-27829 since 02/24/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. The technical details are unknown and an exploit is not publicly available.

Upgrading to version 9.5.4 eliminates this vulnerability. Applying the patch e01e98b063e90d274c42130ec2a60cc0966622c9 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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