MAL-2026-17598 Malicious code in eth-keystore-utils (RubyGems)

RubyGems runs this gem's native extension script ext/req_throttle_mini/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, forks twice into a detached process, waits 20 to 40 minutes and opens a reverse shell that connects /bin/sh to 45.138.12.177 on TCP port 8090. The shell reconnects every 30 seconds. 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 advertises itself as an Ethereum keystore helper but ships a native extension (ext/req_throttle_mini/extconf.rb) whose sole purpose is to execute a malicious payload during gem install. The extconf script base64-decodes an embedded Ruby payload and evals it inside a double-forked, detached child process, then writes an empty Makefile via create_makefile with no C sources present. The decoded payload opens a TCP connection to the hardcoded bare-IP C2 at 45.138.12.177:8090, pipes the socket to /bin/sh via IO.popen and IO.copy_stream in both directions, and reconnects on failure in a loop, giving the operator a persistent remote shell on the installer's host. The dropper is gated by anti-analysis checks: it refuses to fire inside CI, ephemeral or sandbox-shaped hostnames, generated usernames, or analysis path prefixes, requires the presence of developer secrets (~/.ssh, ~/.gitconfig, ~/.npmrc, ~/.gem/credentials, ~/.bundle) and sufficient machine uptime, and sleeps 20–40 minutes after detaching before executing to evade install-time scanners. The lib/ module is a thin JSON reader that serves as cover; the native extension ships no real build sources. Package naming targets Ethereum developers likely to hold wallet material and cloud/VCS credentials on their workstations.

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

It is considered malicious because:

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