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GMO Flatt Security

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KindaRails2Shell threatens Ruby on Rails apps (CVE-2026-66066)

Critical CVE-2026-66066 in Rails' Active Storage/libvips allows unauthenticated arbitrary file read and possible RCE; active exploitation now observed.

CVE-2026-66066 (KindaRails2Shell), discovered by Ethiack researchers and independently by RyotaK of GMO Flatt Security, lets attackers upload crafted files that exploit libvips' handling of specialty formats to read arbitrary files, including process environment secrets, potentially escalating to RCE. Default Rails 7.0+ setups using Active Storage with the vips processor are affected before versions 7.2.3.2, 8.0.5.1, and 8.1.3.1; fixes shipped July 29, 2026, with VIPS_BLOCK_UNTRUSTED as a partial mitigation. Proof-of-concept exploits circulated after disclosure, and VulnCheck updated that it observed active exploitation originating from a single French IP establishing C2 to a host in Israel. Akamai deployed WAF rules, but experts stress patching and credential rotation over filtering alone.

Help Net Security · 15d agoVulnerability in the wildCVE-2026-66066

Related CVEs

  • Unauthenticated Arbitrary File Read in Ruby on Rails Active Storage
    CVE-2026-66066 is a flaw in Active Storage (part of Ruby on Rails' Action Pack) in which libvips operations that are marked unsafe for untrusted content are not disabled, so a crafted upload can invoke such an operation on the server. It is triggered when an unauthenticated attacker uploads a maliciously crafted image to a Rails application that is configured to use libvips and accepts image uploads from untrusted users. Successful exploitation lets the attacker read arbitrary files accessible to the Rails process, including environment variables and application secrets; leaked credentials such as secret_key_base or external-service tokens can be leveraged for remote code execution or lateral movement. Affected applications are those running Rails 7.2.x, 8.0.x or 8.1.x before the patched releases 7.2.3.2, 8.0.5.1 and 8.1.3.1, provided Active Storage with libvips is in use. Public exploit code is not yet documented, but news reports describe active attacks against Rails apps (a campaign referred to as "KindaRails2Shell"), EPSS assigns a 27.9% probability of exploitation within 30 days (98th percentile), and the flaw is not yet listed in CISA KEV.
    · Ruby on Rails Active Storage (Action Pack) 7.2.x prior to 7.2.3.2 · Ruby on Rails Active Storage (Action Pack) 8.0.x prior to 8.0.5.1mass

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