Not running, but supported. You can check your app with:

    bin/rails runner '
      require "vips"
      puts "ruby-vips #{Vips::VERSION}  libvips #{Vips.version(0)}.#{Vips.version(1)}.#{Vips.version(2)}"
      begin
        Vips::Operation.new("matload")
        puts "matload PRESENT - this build can reach libmatio"
      rescue Vips::Error
        puts "matload ABSENT - this build cannot reach libmatio"
      end
    '

This is from the Rails official docs for the CVE which, interestingly, they only released as an agent skill. https://github.com/rails/rails-forensics-CVE-2026-66066/blob...