MAL-2026-17614 Malicious code in wallet-backup-tool (RubyGems)

RubyGems runs this gem's native extension script ext/wallet-backup-tool/extconf.rb during gem install. The script exits without action on CI runners and sandboxes, based on CI environment variables, the hostname, the username and the working directory. It continues if the system uptime is over 30 minutes and the home directory holds .ssh, .gitconfig, .npmrc, .gem/credentials or .bundle. It then decodes a Base64 Ruby payload and forks twice into a detached process. After 20 to 40 minutes the payload downloads http://45.138.12.177:8092/wgkit.tar.gz to /tmp/.w1.tgz with curl, extracts it to /tmp/.w1/, runs wg_install.sh with bash and deletes both. The payload stores the URL XOR-encoded with the key usv\x9a. The Ruby code in lib/ is a decoy. The RubyGems account reqthrottle_3474 published this gem and 41 others with the same loader on 2026-10-05.

The gem's native extension build script extconf.rb, which executes automatically on gem install, contains a base64-encoded Ruby payload that is eval'd inside a double-forked, detached, FD-redirected child process. Before activating, the payload gates execution on absence of CI environment variables, non-ephemeral hostname, non-generated username, non-analysis working directory, machine uptime greater than 1800 seconds, and the presence of developer dotfiles (~/.ssh, ~/.gitconfig, ~/.gem/credentials, ~/.bundle). After a randomized 20-40 minute sleep, the payload reconstructs a URL by XOR-decoding a hex string, resolving to http://45.138.182.177:809/wgkit.tar.gz, then runs curl to fetch the tarball over plain HTTP to /tmp/.w1.tgz, extracts it, and executes wg_install.sh from the archive via bash. The accompanying C extension (wallet-backup-tool.c) is a one-line empty stub (void Init_WalletBackupTool(void) {}), and the shipped library exposes only a trivial ~50-word hardcoded list rather than the full BIP-39 2048-word list the package name advertises, confirming the native-extension build is a cover for the dropper rather than a real compilation step. The wallet-backup framing combined with the dotfile gating targets developers likely to hold cryptocurrency and credential material.

The OpenSSF Package Analysis project identified 'wallet-backup-tool' @ 1.0.0 (rubygems) as malicious.

It is considered malicious because:

• The package executes one or more commands associated with malicious behavior.