Vulnerability · Published Jul 30, 2026 · Assigned by GitHub_M
CVE-2026-66066Action Pack: Possible arbitrary file read and remote code execution in Active Storage variant processing
Critical 9.5
In plain English
A critical-severity security flaw in rails from rails. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 30.1% (higher than 98% of all known vulnerabilities). Ready-made attack tooling exists: Metasploit, public proof-of-concept code. Fixed versions are available - upgrade the affected package.
Official 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 packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | rails | 2:6.1.7.10+dfsg-1~deb12u3 | DEBIAN-CVE-2026-66066 |
| Debian:13 | rails | 2:7.2.2.2+dfsg-2~deb13u2 | DEBIAN-CVE-2026-66066 |
| Debian:14 | rails | 2:7.2.3.2+dfsg-1 | DEBIAN-CVE-2026-66066 |
| RubyGems | activestorage | 8.0.5.1 | GHSA-xr9x-r78c-5hrm |
| RubyGems | activestorage | 7.2.3.2 | GHSA-xr9x-r78c-5hrm |
| RubyGems | activestorage | 8.1.3.1 | GHSA-xr9x-r78c-5hrm |
| Ubuntu:24.04:LTS | rails | no fix listed | UBUNTU-CVE-2026-66066 |
| Ubuntu:26.04:LTS | rails | no fix listed | UBUNTU-CVE-2026-66066 |
| Ubuntu:26.10 | rails | no fix listed | UBUNTU-CVE-2026-66066 |
Affected products (as reported)
Weakness: CWE-1188 · Vector: 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
References
- https://github.com/rails/rails/security/advisories/GHSA-xr9x-r78c-5hrm x_refsource_CONFIRM
- https://github.com/rails/rails/commit/1c01bb587206ee6eb0e1179c2cef96a6a47acb1e x_refsource_MISC
- https://github.com/rails/rails/commit/349e7a5d5b4b715af1e416db824f3c078a7d59e5 x_refsource_MISC
- https://github.com/rails/rails/commit/d79b7f4aa17dec8ce4960fef05733c8c0c7ef49a x_refsource_MISC
- https://github.com/rails/rails/releases/tag/v7.2.3.2 x_refsource_MISC
- https://github.com/rails/rails/releases/tag/v8.0.5.1 x_refsource_MISC
- https://github.com/rails/rails/releases/tag/v8.1.3.1 x_refsource_MISC
- https://github.com/rubysec/ruby-advisory-db/blob/master/gems/activestorage/CVE-2026-66066.yml x_refsource_MISC
- https://thehackernews.com/2026/07/critical-rails-flaw-could-let.html x_refsource_MISC
- 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-2026-66066 exploit