Public Exposure of Astro Server Source Code via Sourcemaps

Published Date: December 19, 2024

Package Affected Versions Patched Versions Severity
📦 astro (npm) >= 5.0.0-alpha.0, <= 5.0.7 5.0.8 High

Description

Summary:


A bug in Astro’s build process exposes server source code when sourcemaps are enabled. Attackers can retrieve .map files from public servers, which allows reconstruction of the source code.

Affected Versions:



  • Astro 5: Versions >= 5.0.0-alpha.0 to 5.0.7

  • Astro 4: Versions <= 4.16.17


Fixed Versions:



  • Astro 5: Version 5.0.8

  • Astro 4: Version 4.16.18


Impact:



  1. What’s exposed:

    • Server source code.

    • Files under src/pages are particularly easy to predict and access.



  2. What’s NOT exposed:

    • Secrets or environment variables unless directly hardcoded in the source.



  3. Potential consequences:

    • Malicious actors could use the revealed code to discover additional vulnerabilities.

    • Exploitation may involve attacks like denial-of-service (e.g., through unsafe regular expressions in the code).



  4. Severity:

    • Network-based attack vector.

    • Requires no privileges or user interaction.

    • Low complexity to exploit.



Patches & Workarounds

Remediation:



  • For server-output (SSR) projects: Update to Astro 5.0.7 or later.

  • For static-output (SSG) projects: Update to Astro 5.0.8 or later. If using Astro 4, update to 4.16.18.


Recommendations:



  1. Immediate actions:

    • Disable sourcemaps in production if they are not strictly required.

    • Update to a patched version immediately.



  2. Verify updates:

    • Check the dist/client directory after the build to ensure .map files are no longer present.



  3. Best practices:

    • Avoid embedding sensitive information directly in source code.

    • Regularly review build configurations for security issues.




By fixing this issue promptly and avoiding sourcemaps in production, you can mitigate the risk of exposing your server code. Remember: an exposed .map file might feel like sharing your diary in public—it’s never intentional and always awkward.

References

https://github.com/withastro/astro/blob/176fe9f113fd912f9b61e848b00bbcfecd6d5c2c/packages/astro/src/core/build/static-build.ts#L139
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