CVE-2026-66066
Action Pack: Possible arbitrary file read and remote code execution in Active Storage variant processing
- State
- Published
- Severity
- 9.5 Critical
- Published
- Jul 30, 2026
- Updated
- Aug 5, 2026
- Reserved
- Jul 23, 2026
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 4.0 | 9.5 Critical | CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H | GitHub_M |
Weaknesses
- CWE-1188 Insecure Default Initialization of Resource
Affected Products
| Product | Versions |
|---|---|
railsrails |
|
References
- https://github.com/rails/rails/security/advisories/GHSA-xr9x-r78c-5hrm
- 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/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
- https://ethiack.com/info-hub/research/kindarails2shell-rails-rce-cve-2026-66066
- http://www.openwall.com/lists/oss-security/2026/08/01/6
- https://github.com/rails/rails-forensics-CVE-2026-66066exploit
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