CVE-2026-54299: CWE-20: Improper Input Validation in withastro astro
Astro is a web framework. Prior to 6.4.6, Astro SSR apps with prerendered error pages (/404 or /500 using export const prerender = true) fetch those pages over HTTP at runtime when an error occurs. The URL for this fetch is derived from request.url, which in turn gets its origin from the incoming Host header. When the Host header is not validated against allowedDomains, an attacker can point the fetch at an arbitrary host and read the response. This vulnerability is fixed in 6.4.6.
AI Analysis
Technical Summary
CVE-2026-54299 describes an improper input validation vulnerability (CWE-20) in the Astro web framework prior to version 6.4.6. Specifically, SSR applications with prerendered error pages (/404 or /500) fetch these pages at runtime using a URL derived from request.url, which in turn uses the origin from the incoming Host header. Because the Host header is not validated against a whitelist (allowedDomains), an attacker can supply a malicious Host header to cause the application to fetch error pages from arbitrary hosts, potentially exposing sensitive data. This vulnerability is resolved in Astro version 6.4.6.
Potential Impact
An attacker can exploit this vulnerability by sending a crafted Host header to an affected Astro SSR app with prerendered error pages, causing the app to fetch error pages from an attacker-controlled or arbitrary host. This can lead to unauthorized disclosure of information (high confidentiality impact) and partial integrity loss (low impact). Availability is not affected. The CVSS 3.1 score is 7.5 (high severity).
Mitigation Recommendations
Upgrade Astro to version 6.4.6 or later, where this vulnerability is fixed by validating the Host header against allowedDomains before using it to construct fetch URLs. Until upgrading, ensure that the Host header is properly validated or restricted to trusted domains to prevent exploitation.
CVE-2026-54299: CWE-20: Improper Input Validation in withastro astro
Description
Astro is a web framework. Prior to 6.4.6, Astro SSR apps with prerendered error pages (/404 or /500 using export const prerender = true) fetch those pages over HTTP at runtime when an error occurs. The URL for this fetch is derived from request.url, which in turn gets its origin from the incoming Host header. When the Host header is not validated against allowedDomains, an attacker can point the fetch at an arbitrary host and read the response. This vulnerability is fixed in 6.4.6.
CVSS v3.1
Score 7.5high
Affected software
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-54299 describes an improper input validation vulnerability (CWE-20) in the Astro web framework prior to version 6.4.6. Specifically, SSR applications with prerendered error pages (/404 or /500) fetch these pages at runtime using a URL derived from request.url, which in turn uses the origin from the incoming Host header. Because the Host header is not validated against a whitelist (allowedDomains), an attacker can supply a malicious Host header to cause the application to fetch error pages from arbitrary hosts, potentially exposing sensitive data. This vulnerability is resolved in Astro version 6.4.6.
Potential Impact
An attacker can exploit this vulnerability by sending a crafted Host header to an affected Astro SSR app with prerendered error pages, causing the app to fetch error pages from an attacker-controlled or arbitrary host. This can lead to unauthorized disclosure of information (high confidentiality impact) and partial integrity loss (low impact). Availability is not affected. The CVSS 3.1 score is 7.5 (high severity).
Mitigation Recommendations
Upgrade Astro to version 6.4.6 or later, where this vulnerability is fixed by validating the Host header against allowedDomains before using it to construct fetch URLs. Until upgrading, ensure that the Host header is properly validated or restricted to trusted domains to prevent exploitation.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-06-12T17:46:37.293Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 6a398861eed863c81e5021ce
Added to database: 06/22/2026, 19:09:21 UTC
Last enriched: 06/29/2026, 21:53:16 UTC
Last updated: 08/06/2026, 12:41:11 UTC
Views: 83
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