CVE-2024-56159: 
JavaScript vulnerability analysis and mitigation

Astro, a web framework for content-driven websites, contains a vulnerability (CVE-2024-56159) that allows unauthenticated users to read parts of the server source code. During the build process, sourcemap files for server code are moved to a publicly-accessible folder, which can be accessed via unauthorized HTTP GET requests. The vulnerability affects server-output projects on Astro 5 versions v5.0.3 through v5.0.7, and static-output projects using Astro 4 versions 4.16.17 or older, or Astro 5 versions 5.0.8 or older, with sourcemaps enabled (GitHub Advisory).

The vulnerability stems from a bug in the build process where sourcemap files for server code are incorrectly moved to a public folder alongside client assets. While some server files are hashed, files corresponding to the file system router (in src/pages) are predictably named. For example, the sourcemap file for src/pages/index.astro is named dist/client/pages/index.astro.mjs.map. The vulnerability has been assigned a CVSS v4.0 score of 7.8 (High), with attack vector being Network, low attack complexity, and no privileges or user interaction required (GitHub Advisory).

The immediate impact is limited to source code exposure. While secrets and environment variables are not directly exposed unless present in the source code, the vulnerability can lead to the discovery of additional vulnerabilities through the revealed source code. There is no immediate impact on server integrity, but exposed code could reveal vulnerabilities that might compromise server availability, such as unsafe regular expressions (GitHub Advisory).

The vulnerability has been patched in multiple versions: astro@5.0.8 for server-output projects, and astro@5.0.9 (also backported to astro@4.16.18) for static-output projects. Users are strongly advised to update immediately if they are using sourcemaps or an integration that enables sourcemaps (GitHub Advisory).