What’s Vulnerable › Vulnerabilities

CVE-2026-66066: Action Pack: Possible arbitrary file read and remote code execution in Active Storage variant processing

• Severity: critical (CVSS 9.5 v4.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 30.1% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-07-30 · updated 2026-09-10
• Weakness: CWE-1188

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.

Affected products

• Rubygems Activestorage: before 7.2.3.2; from 8.0.0.beta1 before 8.0.5.1; from 8.1.0.beta1 before 8.1.3.1; 0.1, 5.2.0, 5.2.0.beta1, 5.2.0.beta2, 5.2.0.rc1, 5.2.0.rc2 (+175) — fixed in 7.2.3.2, 8.0.5.1, 8.1.3.1
• Ruby on Rails: before 7.2.3.2; from 8.0.0.beta1, < 8.0.5.1; from 8.1.0.beta1, < 8.1.3.1

How to fix

Upgrade to a fixed version: Rubygems Activestorage 7.2.3.2, 8.0.5.1, 8.1.3.1. Check the vendor advisory for mitigations.

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
• https://thehackernews.com/2026/07/critical-rails-flaw-could-let.html
• http://www.openwall.com/lists/oss-security/2026/07/29/9
• http://www.openwall.com/lists/oss-security/2026/08/01/6
• https://ethiack.com/info-hub/research/kindarails2shell-rails-rce-cve-2026-66066

Get alerted when CVE-2026-66066 or the next vulnerability affects your stack