6.5

CVSS Score

3.1

-

CVSS Score

Basic Information

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CVE-2026-27829

CVE-2026-27829: Astro is vulnerable to SSRF due to missing allowlist enforcement in remote image inferSize

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.

(GitHub Advisory)

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CVE-2026-27829

CVE-2026-27829:

6.5

CVSS Score

3.1

-

CVSS Score

Basic Information

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Technical Details

Package Name	Ecosystem	Vulnerable Versions	First Patched Version
@astrojs/node	npm	>= 9.0.0, < 9.5.4	9.5.4

Technical Details

Vulnerability Intelligence
Miggo AI

Root Cause Analysis

The vulnerability is a Server-Side Request Forgery (SSRF) in the Astro image processing pipeline. The root cause is twofold. First, the getImage function, when used with the inferSize: true option for remote images, would call the inferRemoteSize function without validating the image URL against the configured image.domains or image.remotePatterns allowlists. The inferRemoteSize function would then proceed to fetch the URL directly, allowing an attacker who can control the image source to make the server issue requests to any URL, including internal network services.

Second, several loadRemoteImage functions across the codebase were vulnerable to SSRF via open redirects. These functions used the fetch API without explicitly disabling redirects. An attacker could supply a URL from an allowed domain that redirects to a restricted internal or external service, and the server would follow the redirect, bypassing the security controls. The patch addresses both issues by adding allowlist checks before inferring image sizes and by explicitly disabling redirects in all remote image fetching operations.

Vulnerable functions

getImage

packages/astro/src/assets/internal.ts

The `getImage` function was vulnerable because when the `inferSize` option was used for a remote image, it would call `inferRemoteSize` to fetch the image dimensions without first verifying if the remote image's domain was in the user's configured allowlist (`image.domains` or `image.remotePatterns`). This allowed an attacker to trigger server-side requests to arbitrary URLs.

inferRemoteSize

packages/astro/src/assets/utils/remoteProbe.ts

The `inferRemoteSize` function was the core of the SSRF vulnerability. It received a URL and directly used `fetch(url)` to get the image content for dimension analysis. It did not perform any validation to ensure the URL was on an allowlist, nor did it prevent HTTP redirects, making it a direct vector for SSRF.

Vulnerability Intelligence
Miggo AI

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WAF Rule

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Reasoning

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