MAL-2026-17586 Malicious code in bitcoin-address-utils (RubyGems)

RubyGems runs this gem's native extension script ext/bitcoin-address-utils/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 runs automatically during gem install, decodes a base64-wrapped Ruby payload that XOR-decodes a hardcoded URL (approximately http://45.13.8.12:8092/wgkit.tar.gz, overridable via ENV['WG_KIT_URL']), downloads a tarball to /tmp/.w1.tgz, extracts it, and executes the embedded wg_install.sh via bash. Execution is double-forked and detached so it survives after the install process exits. The shipped C extension source is a two-line empty stub, so the extension exists only to run the dropper. The script contains anti-analysis gating: it refuses to execute inside CI, on ephemeral or sandbox hosts, under usernames matching /uA\d+|sandbox|tester|analys|scanner/, on analysis paths such as /tmp, /var/tmp, /opt/rubygems, /workspace, and on hosts with uptime below 1800 seconds, and only detonates when developer-signal files exist (~/.ssh, ~/.gitconfig, ~/.npmrc, ~/.gem/credentials, ~/.bundle). A 20-40 minute random sleep precedes execution. The attacker-controlled endpoint is a bare IP on a non-standard port with no pinning, hash verification, or TLS, and the staged payload is executed from a hidden /tmp path.

The OpenSSF Package Analysis project identified 'bitcoin-address-utils' @ 1.0.0 (rubygems) as malicious.

It is considered malicious because:

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