CVE-2026-27829

MediumPublic PoC

Published: 26 February 2026

Published

26 February 2026

Modified

09 March 2026

KEV Added

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Patch

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CVSS Score 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L

EPSS Score 0.0008 22.7th percentile

Risk Priority 13 60% EPSS · 20% KEV · 20% CVSS

Summary

CVE-2026-27829 is a medium-severity SSRF (CWE-918) vulnerability in Astro \@Astrojs\/Node. Its CVSS base score is 6.5 (Medium).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 22.7th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.

Threat & Defense at a Glance

What attackers do: exploitation maps to Exploit Public-Facing Application (T1190) and 1 other technique.

Threat & Defense Details

Likely Mitigating ControlsAI

Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.

CA-8 Penetration Testing

addresses: CWE-918

Penetration testing attempts server-side requests to internal resources, identifying SSRF weaknesses for remediation.

SC-7 Boundary Protection

addresses: CWE-918

Outbound connections to external resources can be monitored and limited at the boundary, reducing SSRF impact.

SI-10 Information Input Validation

addresses: CWE-918

Validates server-side URLs and resource references to block SSRF attempts.

SI-4 System Monitoring

addresses: CWE-918

Detects server-side request forgery through monitoring of unexpected outbound connections.

MITRE ATT&CK Enterprise TechniquesAI

T1190 Exploit Public-Facing Application Initial Access

Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.

attack.mitre.org →

T1522 Cloud Instance Metadata API Credential Access

Adversaries may attempt to access the Cloud Instance Metadata API to collect credentials and other sensitive data.

attack.mitre.org →

Why these techniques?

SSRF in public-facing Astro image pipeline (bypassing domain restrictions) directly enables exploitation of the web app (T1190) and access to cloud instance metadata endpoints (T1522).

Confidence: HIGH · MITRE ATT&CK Enterprise v18.1

NVD 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.

Deeper analysisAI

CVE-2026-27829 is a vulnerability in the Astro web framework, affecting versions 9.0.0 through 9.5.3. The issue resides in Astro's image pipeline, where the `inferSize` option fetches remote images at render time to determine their dimensions without performing domain validation. This allows bypassing the `image.domains` or `image.remotePatterns` restrictions that developers configure to limit fetches to authorized hosts only.

An attacker who can influence the image URL—such as through CMS content or user-supplied data—can exploit this to force the Astro server to fetch content from arbitrary remote hosts. This enables server-side request forgery (SSRF), including against internal network services or cloud metadata endpoints, with a CVSS v3.1 base score of 6.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L) and mapping to CWE-918.

The Astro security advisory (GHSA-cj9f-h6r6-4cx2) and corresponding commit (e01e98b063e90d274c42130ec2a60cc0966622c9) confirm that upgrading to version 9.5.4 resolves the issue by enforcing domain validation during `inferSize` fetches.