CVE-2024-56159 in astro
Summary
by MITRE • 12/19/2024
Astro is a web framework for content-driven websites. A bug in the build process allows any unauthenticated user to read parts of the server source code. During build, along with client assets such as css and font files, the sourcemap files **for the server code** are moved to a publicly-accessible folder. Any outside party can read them with an unauthorized HTTP GET request to the same server hosting the rest of the website. While some server files are hashed, making their access obscure, the files corresponding to the file system router (those in `src/pages`) are predictably named. For example. the sourcemap file for `src/pages/index.astro` gets named `dist/client/pages/index.astro.mjs.map`. This vulnerability is the root cause of issue #12703, which links to a simple stackblitz project demonstrating the vulnerability. Upon build, notice the contents of the `dist/client` (referred to as `config.build.client` in astro code) folder. All astro servers make the folder in question accessible to the public internet without any authentication. It contains `.map` files corresponding to the code that runs on the server. All **server-output** projects on Astro 5 versions **v5.0.3** through **v5.0.7**, that have **sourcemaps enabled**, either directly or through an add-on such as `sentry`, are affected. The fix for **server-output** projects was released in **[email protected]**. Additionally, all **static-output** projects built using Astro 4 versions **4.16.17 or older**, or Astro 5 versions **5.0.8 or older**, that have **sourcemaps enabled** are also affected. The fix for **static-output** projects was released in **[email protected]**, and backported to Astro v4 in **[email protected]**. The immediate impact is limited to source code. Any secrets or environment variables are not exposed unless they are present verbatim in the source code. There is no immediate loss of integrity within the the vulnerable server. However, it is possible to subsequently discover another vulnerability via the revealed source code . There is no immediate impact to availability of the vulnerable server. However, the presence of an unsafe regular expression, for example, can quickly be exploited to subsequently compromise the availability. The fix for **server-output** projects was released in **[email protected]**, and the fix for **static-output** projects was released in **[email protected]** and backported to Astro v4 in **[email protected]**. Users are advised to update immediately if they are using sourcemaps or an integration that enables sourcemaps.
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Analysis
by VulDB Data Team • 11/27/2025
The vulnerability described in CVE-2024-56159 represents a critical information disclosure flaw within the Astro web framework that affects server-side source code exposure during the build process. This issue stems from improper handling of source map files generated during compilation, where server-side code map files are inadvertently placed in publicly accessible directories without authentication mechanisms. The vulnerability specifically impacts Astro versions 5.0.3 through 5.0.7 for server-output projects and older versions of static-output projects, creating a significant security risk that aligns with CWE-200 (Information Exposure) and CWE-540 (Inclusion of Sensitive Information in Source Code) classifications. The flaw manifests when the build process moves server-side source map files to the dist/client directory, which remains accessible to unauthenticated users, effectively exposing sensitive server-side implementation details.
The technical exploitation of this vulnerability occurs through straightforward HTTP GET requests targeting the publicly accessible source map files, which contain detailed mappings between compiled code and original source files. The predictability of file naming conventions, such as dist/client/pages/index.astro.mjs.map for the index.astro file, allows attackers to systematically access these files and reconstruct server-side code implementations. This exposure extends to the file system router components located in src/pages directory, where the mapping between routes and handler functions becomes visible to any external party. The vulnerability's impact is particularly concerning because while environment variables and secrets are not directly exposed unless hardcoded into source files, the revealed code structure enables attackers to identify potential attack vectors, including unsafe regular expressions or other implementation flaws that could later be exploited for more severe compromise. The ATT&CK framework classification would place this under T1595.001 (Network Device Discovery) and T1566.001 (Phishing via Social Engineering) as attackers could leverage the exposed information for further reconnaissance and targeted attacks.
The operational impact of this vulnerability extends beyond simple code exposure, as it creates a foundation for subsequent attacks that could compromise system integrity and availability. While the immediate threat does not include direct data loss or service disruption, the exposure of server implementation details provides attackers with valuable intelligence for identifying additional vulnerabilities within the application. The presence of source code reveals potential insecure coding practices, such as unsafe regular expressions or improper input validation, which could be exploited to cause denial of service or other compromise scenarios. Organizations using Astro frameworks with sourcemaps enabled face a heightened risk of advanced persistent threats where the initial information disclosure serves as a foothold for more sophisticated attacks. The vulnerability affects both server-output and static-output projects, with different fix versions for each type - Astro 5.0.8 for server-output projects and Astro 5.0.9 with backport to Astro 4.16.18 for static-output projects, indicating the severity and widespread nature of the issue. The risk assessment should consider that this vulnerability could enable attackers to identify and exploit other weaknesses in the system architecture, potentially leading to complete system compromise through subsequent exploitation vectors.
The recommended mitigation strategy involves immediate update of affected Astro framework versions to the patched releases, specifically astro5.0.8 for server-output projects and astro5.0.9 with backport to [email protected] for static-output projects. Organizations should also implement immediate remediation measures including disabling sourcemaps in production environments until the framework updates are applied, and reviewing existing deployments for any evidence of unauthorized access to the exposed source map files. Security teams should conduct comprehensive vulnerability assessments to identify all affected projects and ensure that the updated framework versions are properly implemented across all environments. The patch addresses the root cause by ensuring that server-side source map files are not placed in publicly accessible directories during the build process, thereby eliminating the unauthorized access vector while maintaining the development benefits of sourcemaps in non-production environments. Additional defensive measures include network segmentation, access control policies, and monitoring for unusual access patterns to build artifacts that could indicate exploitation attempts.