Description

The gem's native-extension script (ext/.../extconf.rb) embeds a base64-encoded Ruby payload that is eval'd at gem install time. The payload double-forks and detaches a background process which sleeps 20-40 minutes, reconstructs a C2 URL by XOR-decoding a hex blob to http://45.138.17.70:809/wgkit.tar.gz, downloads the tarball to /tmp/.w1.tgz, extracts it to /tmp/.w1, and executes wg_install.sh as the installing user. Execution is gated on anti-analysis checks that suppress the payload in CI, ephemeral/sandbox hostnames, generated usernames matching /uA\d+/, paths under /tmp or /opt/rubygems, and hosts with short uptime, and requires developer-machine signals such as ~/.ssh, ~/.gitconfig, and ~/.gem/credentials before firing. The advertised purpose (Bitcoin transaction broadcast helpers over public esplora endpoints) is a decoy: the shipped library only exposes a truncated BIP39 word list with no broadcast code, and the native extension's C source is an empty Init_ stub. The extconf.rb dropper is the gem's only functional component.

Mitigation

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References