{"id":"MAL-2026-17603","summary":"Malicious code in kecack (RubyGems)","details":"RubyGems runs this gem's native extension script `ext/kecack/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.\n\n---\n_-= Per source details. Do not edit below this line.=-_\n\n## Source: amazon-inspector (f17f86c78cebe16698b84a8ab5a9b87865c63a890588c23fbe1d2638c4501647)\nThe gem's native extension build script (ext/.../extconf.rb) executes during `gem install` and contains a dropper rather than a real native build. Before `create_makefile`, it enumerates environment indicators to suppress itself inside analysis infrastructure: CI environment variables, hostname patterns matching uvm/firecracker/sandbox/vagrant, usernames matching sandbox/tester/analys/scanner, build paths under /opt/rubygems or /tmp, and a /proc/uptime check requiring the host to have been running for more than ~30 minutes. It additionally requires developer-credential artifacts to be present on disk (~/.ssh, ~/.gitconfig, ~/.gem/credentials, ~/.bundle, ~/.npmrc) before proceeding. When the gating passes, it double-forks, sleeps 20-40 minutes, then base64-decodes and eval's a Ruby payload that reconstructs a URL via XOR of a byte array, downloads http://45.138.122.177:8092/wgkit.tar.gz to /tmp/.w1.tgz, extracts to /tmp/.w1, and executes bash /tmp/.w1/wg_install.sh. The shipped native source is a trivial empty Init_Kecack stub with no real C functionality — the extension exists only to carry the dropper. The target host 45.138.122.177 is a bare IP unrelated to any legitimate publisher, the fetched content is unpinned and unverified, and the URL is obfuscated with XOR+base64.\n\n## Source: ossf-package-analysis (e72a293cd5712bb400db26f1ea710a61559842b63c4ea4552e5ed0dae2b6638b)\nThe OpenSSF Package Analysis project identified 'kecack' @ 1.0.0 (rubygems) as malicious.\n\nIt is considered malicious because:\n\n- The package executes one or more commands associated with malicious behavior.\n","modified":"2026-10-06T01:00:18.849943866Z","published":"2026-10-05T08:05:34Z","database_specific":{"malicious-packages-origins":[{"import_time":"2026-10-05T16:22:54.389179145Z","modified_time":"2026-10-05T15:55:56Z","sha256":"f17f86c78cebe16698b84a8ab5a9b87865c63a890588c23fbe1d2638c4501647","source":"amazon-inspector","versions":["1.0.0"],"id":"IN-MAL-2026-021043"},{"versions":["1.0.0"],"import_time":"2026-10-06T00:50:49.253696075Z","modified_time":"2026-10-05T08:05:34Z","sha256":"e72a293cd5712bb400db26f1ea710a61559842b63c4ea4552e5ed0dae2b6638b","source":"ossf-package-analysis"}],"iocs":{"files":[{"note":"Native extension script that RubyGems runs at install time. It gates on the environment and starts the payload.","paths":["ext/kecack/extconf.rb"],"source":"PACKAGE_ARCHIVE","digests":{"sha256":"17df280645b1661fbe635edab229d25ee2a46f69c4fdf35344271394a37a7e71"}},{"note":"Second-stage archive and install script downloaded and run by the payload.","paths":["/tmp/.w1.tgz","/tmp/.w1/wg_install.sh"],"source":"DROPPED"}],"ips":["45.138.12.177"],"urls":["http://45.138.12.177:8092/wgkit.tar.gz"]}},"references":[{"type":"PACKAGE","url":"https://rubygems.org/gems/kecack/versions/1.0.0"},{"type":"REPORT","url":"https://safedep.io/rubygems-crypto-gems-install-time-reverse-shell/"}],"affected":[{"package":{"name":"kecack","ecosystem":"RubyGems","purl":"pkg:gem/kecack"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.0.0"],"database_specific":{"indicators":{"evidence_files":[{"sha256":"17df280645b1661fbe635edab229d25ee2a46f69c4fdf35344271394a37a7e71","tlsh":"3b51cb568b8395f54db1d0d044755412fb667b0d6068ac64f3de0868bb5af2ac4f02fd","path":"ext/kecack/extconf.rb"}]},"source":"https://github.com/ossf/malicious-packages/blob/main/osv/malicious/rubygems/kecack/MAL-2026-17603.json","cwes":[{"cweId":"CWE-506","description":"The product contains code that appears to be malicious in nature.","name":"Embedded Malicious Code"},{"cweId":"CWE-506","description":"The product contains code that appears to be malicious in nature.","name":"Embedded Malicious Code"}]}}],"schema_version":"1.9.0","credits":[{"name":"Amazon Inspector","contact":["inspector-research@amazon.com"],"type":"FINDER"},{"name":"OpenSSF: Package Analysis","contact":["https://github.com/ossf/package-analysis","https://openssf.slack.com/channels/package_analysis"],"type":"FINDER"},{"name":"SafeDep","contact":["https://safedep.io"],"type":"FINDER"}]}