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Vulnerability record · CVE-2026-66066 · published 30 July 2026

CVE-2026-66066: Insecure default initialization vulnerability

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.

9.5 CVSS 4.0 Critical EPSS 2.1% · top 19.1% CWE-1188 · Insecure default initialization Awaiting Analysis
9.5CVSS 4.0 base score
2.1%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
13References
10 Sep 2026Last modified by NVD

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.

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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:

References

LinkTags
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
https://github.com/rails/rails-forensics-CVE-2026-66066

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Source: NIST National Vulnerability Database (record CVE-2026-66066), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.