CVE-2026-27829 Astro is vulnerable to SSRF due to missing allowlist enforcement in remote image inferSize
Attackers can bypass image domain restrictions to force the server to fetch arbitrary URLs, enabling SSRF against internal services.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-27829?
CVE-2026-27829 is a medium-severity server-side request forgery vulnerability in withastro astro, published on 26 Feb 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. 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.
Weakness: CWE-918
Which versions are affected by CVE-2026-27829?
2 open source packages ship an affected version, including @astrojs/node. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
@astrojs/node npm | From 9.0.0 | 9.5.4 |
@astrojs/node npm | From 9.0.0 | 9.5.4 |
Products include Astro \@Astrojs\/Node.
How do I fix CVE-2026-27829?
Upgrade @astrojs/node to 9.5.4 or later.
Upgrade, and send outbound requests through an allow-list that blocks internal addresses. More about Server-side request forgery.
Is CVE-2026-27829 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-27829 exists.
Other vulnerabilities in withastro astro
Sources
Also known as GHSA-cj9f-h6r6-4cx2.