CVE-2026-66066

CRITICALPre-NVD 9.59.5—
EchelonGraph scoreMEDIUM confidence

This critical-severity CVE scores 9.5 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 1.8%, top 24% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
Elevated
9.5EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 2%CVSS: 9.5Exploit: Elevated riskExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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 v3
9.5
EG Score
9.5(medium)
EG Risk
74(Attend)
EG Risk 74/100SSVC: Attend

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity95% × 45%
Exploitation40% × 40%
Automatability100% × 15%
Action: Remediate soon — notable exploitation risk.
EPSS PROB
2%
EPSS %ILE
76%
KEV
Not listed

Published

July 30, 2026

Last Modified

August 5, 2026

Advisory Details (10)

Auto-updated Aug 1, 2026
🔬 Proof of concept available. Patch available. Sources: github_release, github, github_commit.
generic

oss-security - Rails CVE-2026-66066: Possible arbitrary file read and remote code execution in Active Storage variant processing

http://www.openwall.com/lists/oss-security/2026/07/29/9
generic🟡 PoC Available

Critical Rails Flaw Could Let Unauthenticated Attackers Read Server Files via Image Uploads

https://thehackernews.com/2026/07/critical-rails-flaw-could-let.html
generic

ruby-advisory-db/gems/activestorage/CVE-2026-66066.yml at master · rubysec/ruby-advisory-db · GitHub

https://github.com/rubysec/ruby-advisory-db/blob/master/gems/activestorage/CVE-2026-66066.yml
github Patch Available

Possible arbitrary file read and remote code execution in Active Storage variant processing · Advisory · rails/rails · GitHub

https://github.com/rails/rails/security/advisories/GHSA-xr9x-r78c-5hrm
github_release Patch Available

8.1.3.1

Patch available: rails/rails v8.1.3.1

https://github.com/rails/rails/releases/tag/v8.1.3.1
github_release Patch Available

8.0.5.1

Patch available: rails/rails v8.0.5.1

https://github.com/rails/rails/releases/tag/v8.0.5.1
github_release Patch Available

7.2.3.2

Patch available: rails/rails v7.2.3.2

https://github.com/rails/rails/releases/tag/v7.2.3.2
github_commit

commit d79b7f4aa17d (rails/rails)

Fix landed in rails/rails commit d79b7f4aa17d — awaiting tagged release

https://github.com/rails/rails/commit/d79b7f4aa17dec8ce4960fef05733c8c0c7ef49a
github_commit

commit 349e7a5d5b4b (rails/rails)

Fix landed in rails/rails commit 349e7a5d5b4b — awaiting tagged release

https://github.com/rails/rails/commit/349e7a5d5b4b715af1e416db824f3c078a7d59e5
github_commit

commit 1c01bb587206 (rails/rails)

Fix landed in rails/rails commit 1c01bb587206 — awaiting tagged release

https://github.com/rails/rails/commit/1c01bb587206ee6eb0e1179c2cef96a6a47acb1e

Vendor Advisories for CVE-2026-66066(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Affected Packages

(5 across 5 ecosystems)
Debian:11(1)
PackageVulnerable rangeFixed inDependents
rails2:6.0.3.7+dfsg-2 ... 2:7.2.3.2+dfsg-2 (72 versions)——
Debian:12(1)
PackageVulnerable rangeFixed inDependents
rails2:6.1.7.10+dfsg-1~deb12u1 ... 2:7.2.3.2+dfsg-2 (38 versions)——
Debian:13(1)
PackageVulnerable rangeFixed inDependents
rails2:7.2.2.1+dfsg-7 ... 2:7.2.3.2+dfsg-2 (10 versions)——
Debian:14(1)
PackageVulnerable rangeFixed inDependents
rails2:7.2.2.1+dfsg-7 ... 2:7.2.3.1+dfsg-1 (8 versions)2:7.2.3.2+dfsg-1—
RubyGems(1)
PackageVulnerable rangeFixed inDependents
activestorage8.1.0 ... 8.1.3 (7 versions)8.1.3.1—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 13× in last 7d / 46× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-08-21 00:04 UTCEG score recompute
  2. 2026-08-20 22:56 UTCEPSS rescore
  3. 2026-08-19 19:59 UTCEG score recompute
  4. 2026-08-19 17:04 UTCEPSS rescore
  5. 2026-08-18 15:53 UTCEG score recompute
  6. 2026-08-18 13:48 UTCEPSS rescore
  7. 2026-08-17 19:43 UTCEG score recompute
  8. 2026-08-17 13:47 UTCEPSS rescore
  9. 2026-08-16 17:22 UTCEG score recompute
  10. 2026-08-16 14:56 UTCEPSS rescore
  11. 2026-08-16 05:27 UTCEG score recompute
  12. 2026-08-15 01:41 UTCEG score recompute
  13. 2026-08-15 01:30 UTCEPSS rescore
  14. 2026-08-14 01:52 UTCEG score recompute
  15. 2026-08-13 22:00 UTCEPSS rescore
  16. 2026-08-12 14:09 UTCEG score recompute
  17. 2026-08-12 13:51 UTCEPSS rescore
  18. 2026-08-11 14:20 UTCEG score recompute
  19. 2026-08-11 02:26 UTCEG score recompute
  20. 2026-08-11 00:00 UTCEPSS rescore
  21. 2026-08-08 18:52 UTCEG score recompute
  22. 2026-08-08 16:37 UTCEPSS rescore
  23. 2026-08-07 19:04 UTCEG score recompute
  24. 2026-08-06 15:18 UTCEG score recompute
  25. 2026-08-06 13:47 UTCEPSS rescore
Show 21 more
  1. 2026-08-05 19:28 UTCEG score recompute
  2. 2026-08-05 19:17 UTCEPSS rescore
  3. 2026-08-05 19:17 UTCEPSS rescore
  4. 2026-08-04 18:02 UTCEG score recompute
  5. 2026-08-04 15:10 UTCEPSS rescore
  6. 2026-08-04 13:58 UTCEG score recompute
  7. 2026-08-04 10:39 UTCEPSS rescore
  8. 2026-08-04 05:28 UTCEG score recompute
  9. 2026-08-03 12:08 UTCEG score recompute
  10. 2026-08-03 10:36 UTCEPSS rescore
  11. 2026-08-02 04:17 UTCEG score recompute
  12. 2026-08-02 02:27 UTCEPSS rescore
  13. 2026-08-01 08:25 UTCEG score recompute
  14. 2026-08-01 07:33 UTCEG score recompute
  15. 2026-08-01 04:23 UTCEG score recompute
  16. 2026-08-01 04:16 UTCEPSS rescore
  17. 2026-07-31 20:24 UTCEG score recompute
  18. 2026-07-31 16:25 UTCEG score recompute
  19. 2026-07-30 19:30 UTCEG score recompute
  20. 2026-07-30 18:56 UTCEG score recompute
  21. 2026-07-30 18:55 UTCMITRE cvelistV5first tracked

Publicly available exploits

(5 references)

Working exploit code is in the public domain (5 GitHub PoCs). Defenders should treat patch urgency accordingly — public PoCs typically lead to mass-exploitation within 24-72 hours.

  • GitHub PoCHackSpeak/kindarails2shell-poc
    First seen Aug 3, 2026

    CVE-2026-66066 (KindaRails2Shell) PoC - Rails Active Storage/libvips arbitrary file read to RCE; for authorized security testing

    Open source ↗
  • GitHub PoCHackSpeak/CVE-2026-66066
    First seen Aug 3, 2026

    CVE-2026-66066 (KindaRails2Shell) PoC - Rails Active Storage/libvips arbitrary file read to RCE; for authorized security testing

    Open source ↗
  • GitHub PoC0xsha/KindaRails2Shell
    First seen Jul 31, 2026

    CVE-2026-66066 + File Read, RCE, Scanner, Lab

    Open source ↗
  • GitHub PoCrails/rails-forensics-CVE-2026-66066
    First seen Jul 30, 2026
    Open source ↗
  • GitHub PoCZer0SumGam3/CVE-2026-66066-POC
    First seen Jul 29, 2026

    PoC for CVE-2026-66066 in Ruby on Rails

    Open source ↗

Frequently asked(5)

What is CVE-2026-66066?
CVE-2026-66066 is a critical vulnerability published on July 30, 2026. 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…
When was CVE-2026-66066 disclosed?
CVE-2026-66066 was first published in the National Vulnerability Database on July 30, 2026, with the most recent update on August 5, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-66066 actively exploited?
CVE-2026-66066 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 2% probability of exploitation in the next 30 days, which ranks it in the top 23.7% of all scored CVEs.
What is the CVSS score of CVE-2026-66066?
CVE-2026-66066 has a CVSS v3 base score of 9.5 (NVD).
How do I remediate CVE-2026-66066?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-66066, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-66066

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