node-core-libsnpm
Malicious code in node-core-libs (npm) Remove it immediately and rotate any exposed credentials.
What this malware does
scripts/postinstall.js runs automatically on npm install (Windows only) and behaves as a classic install-time dropper. It XOR-decodes (key 0x5A) a hardcoded host and port to produce node22.lunes.host:3258, performs an HTTP GET to http://node22.lunes.host:3258/nl, writes the response bytes to %TEMP%/ms_<rand>.js, and launches them via a generated wscript.exe //B //nologo <vbs> shim with detached:true and windowsHide. The destination is plain HTTP with no version pin, no hash verification, and no integrity check — any bytes the operator of node22.lunes.host returns are executed on the installer's machine. After dropping the payload the script self-cleans: a _tidy() routine rewrites the package's own package.json to remove scripts.postinstall and scripts.install, then unlinks the postinstall script itself, frustrating post-incident review. The script also writes %TEMP%/.nfc_root as a coordination marker and probes for a sibling package node-fetch-utils (a likely typosquat of node-fetch) referencing a node_launcher.js that patches lockfiles, indicating a multi-package campaign with persistence beyond this tarball. The XOR obfuscation of the C2 host, port, and a changeme-spectre key is deliberate concealment of the destination from registry scanners. Installer impact: running npm install node-core-libs on Windows results in arbitrary attacker-controlled code execution under the installing user's account.
Any computer that has this package installed or running should be considered fully compromised. All secrets and keys stored on that computer should be rotated immediately from a different computer. The package should be removed, but as full control of the computer may have been given to an outside entity, there is no guarantee that removing the package will remove all malicious software resulting from installing it.
Malicious versions
Indicators of compromise (SHA-256)
Detection & response playbook
Backdoor / remote accessFind it
Scan your lockfiles (package-lock.json, pnpm-lock.yaml, yarn.lock, requirements.txt, poetry.lock, etc.) and build artifacts for node-core-libs (2 malicious versions). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging node-core-libs across your stack and pipelines.
If you installed it — respond
node-core-libs establishes remote access, so treat any host that installed it as fully compromised. Isolate the machine, remove the package, rotate all credentials it could reach, and rebuild from a trusted image rather than cleaning in place — a backdoor may have planted additional persistence.
Did it already run?
If node-core-libs was ever installed, its post-install/runtime payload may have already executed. O3's L7 egress monitoring and runtime eBPF sensors detect the credential exfiltration or command-and-control callback after install and block the malicious outbound channel, so you catch and contain the actual compromise — not just the presence of the package.
How O3 protects you
O3 blocks node-core-libs before install through its supply-chain scanner, and if it has already run, detects and severs the exfiltration or C2 callback at runtime through L7 egress monitoring and eBPF.
Frequently asked questions
Campaign
References
Credits
- Amazon Inspector · finder
Detect & block this
O3 blocks node-core-libs-class packages before install and in CI — and if it already ran, its runtime egress monitoring catches the C2 callback and severs the channel.