---
title: "CVE-2026-66066: Active Storage has possible arbitrary file read and remote code execution in Active Storage variant processing"
url: https://erroneo.us/security/cve/CVE-2026-66066/
description: "CVE-2026-66066 (activestorage (RubyGems)): 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…"
type: vulnerability-record
section: "Security Digest"
date_published: 2026-07-30
date_modified: 2026-08-05
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2026-66066"
kev: false
cvss: 9.5
epss: 0.27861
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2026-66066: Active Storage has possible arbitrary file read and remote code execution in Active Storage variant processing

**Signal:** High exploit likelihood. EPSS ranks it in the top 5% of all CVEs for likely exploitation in the next 30 days. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- Not in CISA KEV , but CISA’s SSVC assessment records a public proof-of-concept, so attack code exists.
- EPSS 27.9% , percentile 98: FIRST’s model estimates a 27.9% chance of exploitation activity in the next 30 days, higher than 98% of all scored CVEs (very high). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
- Only applies if your dependency tree includes activestorage (RubyGems) < 7.2.3.2, fixed in 7.2.3.2 ; activestorage (RubyGems) >= 8.0.0.beta1, < 8.0.5.1, fixed in 8.0.5.1 ; activestorage (RubyGems) >= 8.1.0.beta1, < 8.1.3.1, fixed in 8.1.3.1 . Check your lockfile, including transitive dependencies.

## What it is

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 secretkeybase 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

- RubyGems `activestorage` < 7.2.3.2 → fixed: 7.2.3.2
- RubyGems `activestorage` >= 8.0.0.beta1, < 8.0.5.1 → fixed: 8.0.5.1
- RubyGems `activestorage` >= 8.1.0.beta1, < 8.1.3.1 → fixed: 8.1.3.1

## Affected products (CVE record)

- rails rails: < 7.2.3.2, >= 8.0.0.beta1, < 8.0.5.1, >= 8.1.0.beta1, < 8.1.3.1

## Severity

- GitHub_M CVSS 4.0: 9.5 `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 CVSS 4.0: 9.5 `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`

## Exploitation

- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation poc , automatable yes , technical impact total .
- FIRST EPSS (model of 2026-10-21): 27.86% probability of exploitation activity in the next 30 days; percentile 98.

## Sources

- [GitHub Advisory GHSA-xr9x-r78c-5hrm](https://github.com/advisories/GHSA-xr9x-r78c-5hrm)
- [CVE.org record CVE-2026-66066](https://www.cve.org/CVERecord?id=CVE-2026-66066)
- [NVD entry CVE-2026-66066](https://nvd.nist.gov/vuln/detail/CVE-2026-66066)
- [github.com](https://github.com/rails/rails/security/advisories/GHSA-xr9x-r78c-5hrm)
- [github.com](https://github.com/rails/rails/commit/1c01bb587206ee6eb0e1179c2cef96a6a47acb1e)
- [github.com](https://github.com/rails/rails/commit/349e7a5d5b4b715af1e416db824f3c078a7d59e5)
- [github.com](https://github.com/rails/rails/commit/d79b7f4aa17dec8ce4960fef05733c8c0c7ef49a)
- [github.com](https://github.com/rails/rails/releases/tag/v7.2.3.2)
- [github.com](https://github.com/rails/rails/releases/tag/v8.0.5.1)
- [github.com](https://github.com/rails/rails/releases/tag/v8.1.3.1)
- [github.com](https://github.com/rubysec/ruby-advisory-db/blob/master/gems/activestorage/CVE-2026-66066.yml)
- [thehackernews.com](https://thehackernews.com/2026/07/critical-rails-flaw-could-let.html)
- [openwall.com](http://www.openwall.com/lists/oss-security/2026/07/29/9)
- [ethiack.com](https://ethiack.com/info-hub/research/kindarails2shell-rails-rce-cve-2026-66066)
- [openwall.com](http://www.openwall.com/lists/oss-security/2026/08/01/6)
- [github.com](https://github.com/rails/rails-forensics-CVE-2026-66066)
- [cve.org](https://www.cve.org/CVERecord/SearchResults?query=CVE-2026-66066)

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Source page: https://erroneo.us/security/cve/CVE-2026-66066/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt