CVE-2026-66066
EPSS 1.7%Rails patching + downstream backports + credential exposure = urgent triage signal; KEV-listing pending.
What: Arbitrary file read to RCE in Rails Active Storage via libvips image processing; affects Rails applications using Active Storage with untrusted image uploads (CVSS 9.5).
Why it matters: Rails maintainers have patched; NixOS/Mastodon backports confirm real-world deployments triaging. Post #6 documents credential exposure (secret_key_base, database passwords, cloud storage credentials, API tokens). Unauthenticated attack surface (crafted image uploads). No KEV-listed status yet, but urgency reflected in vendor patching and security blog coverage.
Where it's seen: Security research writeups (Ethiack, GMO Flatt Security Blog), Hacker News coverage, GitHub patch PRs across downstream consumers (Mastodon, NixOS), social amplification on Bluesky. Posts reference both libvips and Active Storage as attack vector.
RISK: CRITICAL — Unauthenticated RCE, credential exposure, CVSS 9.5, active vendor patching.
Description
Action Pack is a framework for handling and responding to web requests. In versions prior to 7.2.3.2, 8.0.5.1 and 8.1.3.1, Active Storage does not disable libvips operations marked unsafe for untrusted content, allowing a crafted upload to invoke such an operation. Consuming applications are affected when configured to use libvips and accept image uploads from untrusted users. An unauthenticated attacker may exploit this behavior to read arbitrary files accessible to the Rails process, including environment variables and application secrets. Exposure of credentials such as secret_key_base or external-service tokens may enable remote code execution or lateral movement. This issue has been fixed in versions 7.2.3.2, 8.0.5.1 and 8.1.3.1.
Weaknesses
References
- https://github.com/rails/rails/commit/1c01bb587206ee6eb0e1179c2cef96a6a47acb1e
- https://github.com/rails/rails/commit/349e7a5d5b4b715af1e416db824f3c078a7d59e5
- https://github.com/rails/rails/commit/d79b7f4aa17dec8ce4960fef05733c8c0c7ef49a
- https://github.com/rails/rails/releases/tag/v7.2.3.2
- https://github.com/rails/rails/releases/tag/v8.0.5.1
- https://github.com/rails/rails/releases/tag/v8.1.3.1
- https://github.com/rails/rails/security/advisories/GHSA-xr9x-r78c-5hrm
- https://github.com/rubysec/ruby-advisory-db/blob/master/gems/activestorage/CVE-2026-66066.yml
- +2 more