GCVE-110-OSM-2026-13520

The gem's declared native extension build script ext/hd_wallet_generator/extconf.rb executes a Base64-encoded payload via eval() during gem install. The decoded payload opens a TCP socket to the hardcoded remote host 45.138.12.177:8089 and pipes /bin/sh over it (TCPSocket.new + IO.popen(['/bin/sh'],'r+') + IO.copy_stream), granting a remote operator an interactive shell on the installer's host. Execution is wrapped in a double-forked, detached child with a 20–40 minute sleep to decorrelate the connection from the install event. The payload runs only when a battery of evasion checks pass: no CI environment variables, hostname does not match sandbox/firecracker/vagrant/uvm patterns, username does not match generated/analyst patterns (uA\d+, sandbox, tester, analys, scanner), cwd is not under /tmp or /opt/rubygems, machine uptime exceeds 30 minutes, and developer-signal paths exist on disk (~/.ssh, ~/.gitconfig, ~/.gem/credentials, ~/.bundle, ~/.npmrc). No native source files are shipped; create_makefile is a cover stub so the extension-build pretext never actually builds anything. The package metadata name (hd-wallet-generator) and the README description (bitcoin-rpc-lite) disagree, consistent with a disguised dropper. OBFUSCATION - Decoded Base64 Content in ext/hd_wallet_generator/extconf.rb - recovered 1 ips from decoded/deobfuscated content ADDITIONAL FINDINGS - Homebrew Arbitrary Ruby Execution in ext/hd_wallet_generator/extconf.rb: "eval(" - Homebrew Ruby Process Spawning in ext/hd_wallet_generator/extconf.rb: "fork do" - Ruby C Extension Declaration in ext/hd_wallet_generator/extconf.rb: "require 'mkmf'" PAYLOAD FILES ext/hd_wallet_generator/extconf.rb