CVE-2026-102984 in Astro
Summary
by MITRE • 09/30/2026
Astro is a web framework for content-driven websites. Prior to 11.1.3, the @astrojs/node adapter builds a request URL from the Host header, and a malformed port can make that URL invalid. The recovery path reuses the same malformed host and throws an uncaught TypeError: Invalid URL before routing begins. In the default standalone configuration, the request returns an HTTP 500 response and the server continues running, but when staticHeaders is enabled the synchronous handler does not catch the exception and the Node process terminates. Proxies and CDNs that reject malformed Host headers prevent this path from reaching the origin. The issue affects availability only and does not expose data or permit code execution. This issue is fixed in version 11.1.3.
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Analysis
by VulDB Data Team • 09/30/2026
The vulnerability identified in Astro versions prior to 11.1.3 centers on improper input validation within the @astrojs/node adapter, specifically regarding the handling of HTTP Host headers during request URL construction. As a web framework designed for content-driven websites, Astro relies heavily on accurate routing based on incoming requests. The core technical flaw lies in how the server constructs the internal request URL from the Host header provided by the client or intermediary proxy. When a malformed port value is included within this header, the resulting URL object becomes invalid according to standard URI syntax rules. Instead of gracefully handling this parsing error through established exception management protocols, the recovery mechanism erroneously reuses the same malformed host data in subsequent processing steps. This logical error triggers an uncaught TypeError labeled as Invalid URL before the request routing logic can even begin execution.
From a security impact perspective, this vulnerability is classified strictly as an availability issue rather than a confidentiality or integrity breach. The flaw does not expose sensitive user data nor does it permit arbitrary code execution on the server infrastructure. However, the operational consequences vary significantly depending on the deployment configuration of the Astro application. In the default standalone configuration, the server catches the resulting error and responds with an HTTP 500 Internal Server Error to the client while keeping the Node.js process alive and functional for subsequent requests. This behavior limits the impact to a single failed request but does not compromise system stability. Conversely, when the staticHeaders feature is enabled, the synchronous nature of the handler fails to catch this specific exception type. Consequently, the unhandled TypeError causes the entire Node.js process to terminate abruptly. This results in a complete denial of service for that instance until the server administrator manually restarts the application or an automated monitoring system detects and recovers from the crash.
The attack vector for this vulnerability requires sending HTTP requests with specifically crafted Host headers containing malformed port numbers. While external threat actors could theoretically exploit this to cause temporary outages, the practical risk is often mitigated by network architecture. Most modern reverse proxies, load balancers, and Content Delivery Networks enforce strict validation of incoming request headers and will reject or sanitize malformed Host headers before they ever reach the origin server running Astro. Therefore, direct exploitation typically requires either a misconfigured intermediary that passes through invalid headers or an attacker with direct access to the application port bypassing these protective layers. The vulnerability aligns with CWE-20 Improper Input Validation as it stems from insufficient checking of user-supplied input data before its use in critical system functions. Additionally, the impact on availability corresponds to ATT&CK technique T1499 Endpoint Denial of Service, specifically under the sub-category of resource exhaustion or service disruption via application crashes.
To mitigate this vulnerability and prevent future occurrences similar issues, organizations must upgrade their Astro framework installations to version 11.1.3 or later where the parsing logic has been corrected to handle malformed inputs gracefully without crashing the process. For environments that cannot immediately patch due to dependency constraints, implementing robust input validation at the network perimeter is essential. Security teams should ensure that reverse proxies and CDNs are configured with strict header sanitization rules that reject any Host headers containing non-compliant port numbers or characters outside expected alphanumeric ranges. Furthermore, enabling proper exception handling wrappers in custom middleware can provide an additional layer of defense against uncaught exceptions originating from framework internals. Regular monitoring for unexpected process terminations should also be implemented to detect potential exploitation attempts quickly and minimize downtime through automated restart mechanisms if the patch is not yet applied.