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.