Rails ActiveStorage flaw enables RCE
A vulnerability in Ruby on Rails ActiveStorage variant processing allows remote code execution and arbitrary file read.
Sourcecert.ssi.gouv.fr — open the original
What to check
- Applies to
- The 1 CVE named below. Whether you run an affected version is not assessed: check the versions the source lists.
- Exploitation
- A public exploit is recorded for CVE-2026-66066 (weaponized); no exploitation in the wild is recorded.
CERT-FR issued an advisory for a vulnerability in Ruby on Rails' ActiveStorage component, tracked as CVE-2026-66066. The flaw resides in ActiveStorage's variant processing functionality and can be exploited to achieve arbitrary file read and remote code execution, impacting confidentiality of data on affected systems.
Affected versions include activestorage 8.0.x prior to 8.0.5.1, 8.1.x prior to 8.1.3.1, and versions prior to 7.2.3.2. The Rails project published a security bulletin on July 29, 2026 detailing the issue. Administrators are advised to apply the vendor's patches as referenced in the official Rails security advisory.
Mentioned in this report
Source reporting: https://www.cert.ssi.gouv.fr/avis/CERTFR-2026-AVI-0948
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