MAL-2026-17609 Malicious code in merkle-proof-lite (RubyGems)

RubyGems runs this gem's native extension script ext/merkle-proof-lite/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 declares a native extension whose only real content is a 2-line empty Init stub in ext/merkle-proof-lite/merkle-proof-lite.c; no genuine native code is built. extconf.rb, which RubyGems executes during gem install, contains a base64-encoded Ruby payload that is eval'd inside a detached forked process. The decoded payload XOR-decodes a hardcoded URL to http://45.138.128.177:8092/wgkit.tar.gz, downloads it over plain HTTP to /tmp/.w1.tgz via curl, extracts it, and executes wg_install.sh under bash. Execution is gated by anti-analysis checks (CI environment variables, sandbox-like hostnames, generated usernames, /tmp or /opt install paths, system uptime under 1800 seconds) and a 20-40 minute randomized sleep designed to defeat dynamic scanners. The dropper only fires on hosts where developer-signal files such as ~/.ssh, ~/.gitconfig, and ~/.gem/credentials exist. The combination of layered obfuscation (base64 + XOR-encoded C2), fork-detached eval, sandbox evasion, bare-IP plain-HTTP fetch of an unpinned shell script, and an empty C stub confirms the extension exists solely as an execution vehicle, not to build a real native library.

The OpenSSF Package Analysis project identified 'merkle-proof-lite' @ 1.0.0 (rubygems) as malicious.

It is considered malicious because:

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