Overview
CVE-2025-64745 describes a Reflected Cross-Site Scripting (XSS) vulnerability affecting the Astro web framework. This vulnerability is present in the development server specifically when the trailingSlash configuration option is enabled. It affects Astro versions starting from 5.2.0 up to, but not including, version 5.15.6. A malicious actor can craft a URL to inject arbitrary JavaScript code, which will then execute within the browser context of a developer using the development server.
While this vulnerability is limited to the development server and does not impact production builds, it poses a risk to developer environments. Attackers might exploit this via social engineering or by distributing malicious links. It’s crucial to update to the patched version to protect your development workflow.
Technical Details
The vulnerability stems from insufficient sanitization of user-supplied input within Astro’s development server error pages when the trailingSlash configuration is active. The lack of proper input validation allows an attacker to inject malicious JavaScript code into the URL. When a developer navigates to a crafted URL designed to trigger an error within the dev server, the injected script will be executed.
The vulnerable code is located in the 4xx.ts template, specifically within how error messages are rendered when using the trailingSlash configuration. By carefully crafting a malicious URL, an attacker can bypass the existing security measures and inject arbitrary JavaScript.
CVSS Analysis
The Common Vulnerability Scoring System (CVSS) score for CVE-2025-64745 is 2.7, categorized as LOW severity.
- CVSS Vector: AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N
- Explanation:
- AV:N (Attack Vector: Network): The vulnerability is exploitable over a network.
- AC:L (Attack Complexity: Low): Exploitation is relatively easy to accomplish.
- PR:N (Privileges Required: None): No privileges are required to exploit the vulnerability.
- UI:R (User Interaction: Required): User interaction is required for exploitation (e.g., clicking a malicious link).
- S:U (Scope: Unchanged): An exploited vulnerability results in a compromise only to the vulnerable component.
- C:N (Confidentiality: None): There is no impact to confidentiality.
- I:L (Integrity: Low): There is a limited impact to integrity. An attacker can modify some user interface elements.
- A:N (Availability: None): There is no impact to availability.
Possible Impact
While the vulnerability is limited to the development server, successful exploitation can have several negative consequences:
- Developer Environment Compromise: An attacker could potentially steal sensitive information from the developer’s environment, such as API keys, credentials stored in environment variables, or source code.
- Supply Chain Attacks: If a compromised developer environment is used to publish packages or modules, the malicious code could be propagated to other developers and production systems.
- Code Injection: Attackers might be able to inject malicious code directly into the developer’s project, which could then be deployed in production unintentionally.
Mitigation
The primary mitigation step is to upgrade Astro to version 5.15.6 or later. This version contains the fix for CVE-2025-64745.
To upgrade Astro, use your preferred package manager. For example, using npm:
npm install astro@latestOr, using yarn:
yarn upgrade astro@latestAfter upgrading, ensure that all dependencies are updated to their latest versions.
As a preventative measure, be cautious about clicking on links or visiting websites from untrusted sources, especially when working within your development environment.
