# CVE-2026-66066: Action Pack: Possible arbitrary file read and remote code execution in Active Storage variant processing

- Exploited (CISA KEV): no
- Published: 2026-07-30
- CVSS: 9.5 CRITICAL (v4.0)
- EPSS: 30.1% (98th percentile)
- CWE: CWE-1188

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.

## Edge WAF coverage (claimed by vendors, not measured)

| Vendor | Status | First rule | Days after publication |
|---|---|---|---|
| Cloudflare | Blocks by default | 2026-08-04 | — |
| AWS | No public claim | — | — |
| Microsoft Azure | No public claim | — | — |
| Google Cloud | No public claim | — | — |
| Fastly | Before feed history | — | — |
| F5 | Rule published | 2026-09-16 | 48 |
| Akamai | No public source | — | — |
| OWASP CRS | No public claim | — | — |

### Cloudflare

- 2026-08-04 · updated · rule 89d0243997d24c6ea1d610a23a5b40d6 · default Block
  > Rails - Arbitrary File Read & RCE - CVE:CVE-2026-66066. Previous action: Block. New action: Block. This was labeled as File Upload - RCE.
  Source: https://developers.cloudflare.com/changelog/post/2026-08-04-waf-release/

### F5

- 2026-09-16 · new · rule 200009375
  > Added: signature 200009375 "Ruby on Rails "Active Storage" Arbitrary File Read" (Information Leakage, risk Medium), systems: Ruby. References: CVE-2026-66066.
  Source: https://docs.cloud.f5.com/docs-v2/platform/changelogs/security-details-changelog

"No public claim" means no vendor statement names this CVE; "Before feed history" means the CVE is older than the vendor feed. In both cases generic rules may still block it.

HTML: https://cve.vigilbase.com/cve/CVE-2026-66066 · JSON: https://cve.vigilbase.com/api/v1/cves/CVE-2026-66066