Two Astro Adapter Vulnerabilities: Node DoS via Malformed Host Header and Netlify Image CDN SSRF Risk

What Happened

Two advisories were published for Astro adapters. In @astrojs/node, the adapter builds a request URL from the incoming Host header; if the header contains a malformed port, this can produce an invalid URL. The adapter's recovery path reuses the same malformed host and throws an uncaught TypeError before routing occurs. In the default standalone configuration this results in an HTTP 500 response and the server keeps running, but when the staticHeaders option is enabled, the exception is not caught by the synchronous handler and the Node process terminates. Separately, in @astrojs/netlify, the adapter generates regular expressions to validate remote-image allowlists (image.domains / image.remotePatterns) for the Netlify Image CDN, but these expressions are not anchored to the start of the URL. Because Netlify evaluates them with RegExp.test(), an allowed origin appearing anywhere in a URL's path or query string can satisfy the check even though the actual host is different and attacker-controlled. This can let an unauthenticated request to the public /.netlify/images endpoint cause the Image CDN to fetch attacker-selected URLs.

Technical Cause

CVE-2026-102984 (CWE-248, Uncaught Exception) stems from insufficient validation of the Host header before constructing a URL object; a malformed port value triggers an invalid-URL error that is not handled gracefully in the staticHeaders code path. CVE-2026-102983 (CWE-625, Permissive Regular Expression) stems from allowlist regular expressions that are not anchored to the beginning of the input string, allowing a string match on an allowed domain to succeed even when it does not represent the actual host of the target URL.

Why It Matters

The Node adapter issue affects availability only: it does not expose data or permit code execution, but in the staticHeaders configuration a single malformed request can crash the server process, requiring a restart. The advisory notes that proxies and CDNs that reject malformed Host headers before they reach the origin can prevent this path from being reached. The Netlify adapter issue is a Server-Side Request Forgery (SSRF) enabler: it could let an unauthenticated requester cause the Image CDN to make requests to internal or otherwise unintended targets. The advisory states that Netlify's own egress protections may constrain which targets are reachable, and that image transformation limits make direct response exfiltration difficult; no confidentiality or integrity impact has been demonstrated to date.

Who Is Affected

Sites using the @astrojs/node adapter with the staticHeaders option enabled are affected by CVE-2026-102984; sites in the default standalone configuration experience a less severe HTTP 500 response rather than a crash. Sites using the @astrojs/netlify adapter with image.domains or image.remotePatterns configured for the Netlify Image CDN are affected by CVE-2026-102983. Both vulnerabilities can be triggered by unauthenticated requests and require no user interaction.

Affected Versions

@astrojs/node: versions from 0 up to and including 11.1.2 are affected (CVE-2026-102984). @astrojs/netlify: versions from 5.2.0 up to and including 8.2.3 are affected (CVE-2026-102983).

Fixes and Mitigation

@astrojs/node version 11.1.3 fixes CVE-2026-102984. @astrojs/netlify version 8.2.4 fixes CVE-2026-102983. As a partial mitigation for the Node adapter issue, deploying a proxy or CDN in front of the origin that rejects malformed Host headers can prevent the vulnerable path from being reached, though this is not a substitute for upgrading.

Recommended Action

Upgrade @astrojs/node to version 11.1.3 or later, particularly if staticHeaders is enabled. Upgrade @astrojs/netlify to version 8.2.4 or later if remote-image allowlisting is configured for the Netlify Image CDN. Review deployment configurations to confirm which adapters and options are in use before prioritizing remediation.