CVE-2026-66066

Exploitation

Public exploit code exists. CISA's assessment records a public proof of concept. That is not a report of exploitation in the wild.

SSVC decision

• ExploitationpocPublic proof-of-concept exploit code exists. Not a report of exploitation in the wild.
• AutomatableyesAn attacker can reliably automate reconnaissance through exploitation, so this scales.
• Technical ImpacttotalSuccessful exploitation gives total control of the vulnerable component.

CISA publishes the decision points, not a final SSVC decision. The decision also depends on mission and well-being impact, which is a property of your deployment rather than of the vulnerability.

EPSS probability

26.51% probability of exploitation activity in the next 30 days.

EPSS percentile

Equal to or higher than the score of 97.9% of scored records. A rank, not a probability.

NVD base score

9.5 (CVSS v4.0), scored by the NVD independently of the CNA.

NVD CVSS vector

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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

NVD analysis status

Awaiting Analysis. NVD last modified this record on 2026-09-10.

Red Hat severity

Important. Red Hat's rating for its own products, not a CVSS rating.

Exploit-prediction scores from FIRST. Independent scoring and analysis status from the NVD. Vendor severity from Red Hat. Exploitation assessment and catalog membership from CISA.

Published

2026-07-30 18:32Z3 MO AGO

Last updated

2026-08-05 13:46Z2 MO AGO

Reserved

2026-07-23

Assigning CNA

GitHub_M

Record state

PUBLISHED

Severity

Critical (CVSS 9.5)

CNA CVSS vector

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

Weaknesses

• CWE-1188Initialization of a Resource with an Insecure DefaultBase
• CWE-434Unrestricted Upload of File with Dangerous TypeBase

Data version

5.2

Document digest

38f9c1be397e89293fe2aeed569b4adba8aeff9c7c850de776f328489cc3a172

• github.comhttps://github.com/rails/rails/security/advisories/GHSA-xr9x-r78c-5hrmx_refsource_CONFIRM
• github.comhttps://github.com/rails/rails/commit/1c01bb587206ee6eb0e1179c2cef96a6a47acb1ex_refsource_MISC
• github.comhttps://github.com/rails/rails/commit/349e7a5d5b4b715af1e416db824f3c078a7d59e5x_refsource_MISC
• github.comhttps://github.com/rails/rails/commit/d79b7f4aa17dec8ce4960fef05733c8c0c7ef49ax_refsource_MISC
• github.comhttps://github.com/rails/rails/releases/tag/v7.2.3.2x_refsource_MISC
• github.comhttps://github.com/rails/rails/releases/tag/v8.0.5.1x_refsource_MISC
• github.comhttps://github.com/rails/rails/releases/tag/v8.1.3.1x_refsource_MISC
• github.comhttps://github.com/rubysec/ruby-advisory-db/blob/master/gems/activestorage/CVE-2026-66066.ymlx_refsource_MISC
• thehackernews.comhttps://thehackernews.com/2026/07/critical-rails-flaw-could-let.htmlx_refsource_MISC
• www.openwall.comhttp://www.openwall.com/lists/oss-security/2026/07/29/9
• ethiack.comhttps://ethiack.com/info-hub/research/kindarails2shell-rails-rce-cve-2026-66066
• www.openwall.comhttp://www.openwall.com/lists/oss-security/2026/08/01/6
• github.comhttps://github.com/rails/rails-forensics-CVE-2026-66066exploit