CVE-2026-66066criticalobserved exploitationCWE-1188

CVE-2026-66066: critical vulnerability in rails

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

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99Vexday Risk Score

Patch now. It exploitation observed by VulnCheck, has an official Brazilian government alert and has a working public exploit.

ssvc Actcvss 9.5epss 30%
from disclosure to weaponsame day
Published on NVDJul 30
1st PoCJul 29
metasploitJul 29
VulnCheck+26d
Official alert in Brazil

Brazil's federal government published an alert, recommendation or bulletin that cites this vulnerability.

Source: CTIR Gov (GSI) and CISC Gov.br, under the CC BY-ND 3.0 license.
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
Affected products
rails · rails
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