Overview
A critical reflected Cross-Site Scripting (XSS) vulnerability, identified as CVE-2025-64764, has been discovered in the Astro web framework. This vulnerability affects applications using the server islands feature. It has been patched in Astro version 5.15.8. Users of Astro are strongly advised to update to the latest version as soon as possible to mitigate this risk.
Technical Details
The vulnerability stems from insufficient sanitization of user-supplied input when utilizing server islands. Specifically, any input handled within the component templates of these islands could be exploited, regardless of the intended component behavior. This allows an attacker to inject malicious scripts into the application that will be executed in the victim’s browser. This is a reflected XSS vulnerability, meaning the malicious script is injected through a request and immediately reflected back to the user.
CVSS Analysis
The Common Vulnerability Scoring System (CVSS) has assigned a score of 7.1 to CVE-2025-64764, indicating a HIGH severity level. This score reflects the potential for significant impact on confidentiality, integrity, and availability of the affected systems.
Possible Impact
Successful exploitation of this XSS vulnerability could allow an attacker to:
- Steal sensitive user information, such as cookies or session tokens.
- Deface the website or inject malicious content.
- Redirect users to phishing sites.
- Execute arbitrary code in the victim’s browser.
This vulnerability poses a significant risk to websites and applications built with Astro that utilize the server islands feature.
Mitigation or Patch Steps
The recommended mitigation is to upgrade to Astro version 5.15.8 or later. This version contains the necessary patch to address the XSS vulnerability. To update Astro, use your package manager (npm, yarn, pnpm) to install the latest version:
npm install astro@latest
# or
yarn add astro@latest
# or
pnpm add astro@latest
After updating, redeploy your application to ensure the patch is active.
