rails · rails
The flaw is in Active Storage's variant processing within the Rails framework (Action Pack), where libvips operations marked unsafe for untrusted content are not disabled. Applications are exposed when they use libvips and accept image uploads from untrusted users, and an unauthenticated remote attacker can craft an upload that invokes such an operation to read arbitrary files accessible to the Rails process, including environment variables and secrets.
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.
First seen exploited 32 days after disclosure. Public exploit code (PoC-in-GitHub) was available 1 day before disclosure.
No ATT&CK techniques are linked to this CVE yet. MITRE CTID has not mapped it, and no report passage in the corpus ties it to a technique.
1 package in 1 ecosystem. Main package: activestorage.
Upgrade to 8.1.3.1 or later
gem "activestorage", ">= 8.1.3.1"The first fix for CVE-2026-66066. No other CVE tracked by Patchfirst affects this package.
| If you run | Upgrade to |
|---|---|
| 8.1.0.beta1 up to 8.1.3.1 | 8.1.3.1 |
| 8.0.0.beta1 up to 8.0.5.1 | 8.0.5.1 |
| All versions before 7.2.3.2 | 7.2.3.2 |
“Up to” means the second version is the fix and is not affected.
Pulses are indicator collections that anyone can publish. A mention is not confirmation of exploitation.