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What is CVE-2026-66066? Protecting Your Rails App from Active Storage RCE

Blog post from Fastly

Post Details
Company
Date Published
Author
Matthew Mathur
Word Count
294
Company Posts That Month
2
Language
English
Hacker News Points
-
Post removed?
No
Summary

CVE-2026-66066 is an arbitrary file read vulnerability in the Active Storage component of Rails that can lead to remote code execution (RCE) when exploited alongside libvips versions below 8.13. Rails released patches and advisories on July 29, 2026, to address this issue, affecting Active Storage versions below 7.2.3.2, 8.0 up to 8.0.5.1, and 8.1 up to 8.1.3.1. Fastly's Next-Gen WAF customers can activate a virtual patch for immediate protection while waiting for the underlying components to be patched. To fully mitigate the vulnerability, it is recommended to update Active Storage and libvips to the latest versions. Rails has also provided guidance for forensic analysis to detect potential exploitation, and Ethiack has detailed the vulnerability's cause in their research.

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