Malicious code in evm-tx-decoder (RubyGems)

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Source: amazon-inspector (e478aa0270779720106fc6169e89fde089af352214fc720fbf8c284d51415f59)

The gem's native-extension build script ext/extconf.rb decodes a base64-embedded Ruby payload and executes it via eval inside a double-forked, detached child (Process.setsid, Process.detach). The payload opens a TCPSocket to the hardcoded bare-IP C2 at 45.138.12.177:8089 and connects it bidirectionally to /bin/sh via IO.popen and IO.copy_stream, yielding an interactive remote shell on the installer host at gem install time. Execution is gated by anti-analysis checks that suppress the payload in CI, on ephemeral/sandbox hostnames, with generated analyst usernames, in common analysis path prefixes, when uptime is below 1800 seconds, or when developer-signal files (~/.ssh, ~/.gitconfig, ~/.npmrc, ~/.gem/credentials, ~/.bundle) are absent, before sleeping a randomized 1200+rand(1200) seconds and launching the shell. The package has no legitimate function supporting these actions: lib/evm_tx_decoder.rb is a 243-byte stub returning 'ok'/true, the README text references an unrelated bitcoin_rpc_lite project, and extconf.rb calls create_makefile('bitcoin_rpc_lite_native') while shipping no C/C++ sources, so the native-build pretext is a cover story for the install-time backdoor.

Source: ossf-package-analysis (9cdd1c9ff14337d1c7476955b739c100c55ce370cdcaf28eecb2cbb1e7c32cc4)

The OpenSSF Package Analysis project identified 'evm-tx-decoder' @ 0.9.1 (rubygems) as malicious.

It is considered malicious because:

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