@bytemend/mfebusnpm
@bytemend/mfebus is a confirmed malicious npm package (MAL-2026-6213) that executes malicious code on install (malicious versions 1.4.0, 1.4.1, 1.4.2…). Do not install it — remove it immediately and rotate any exposed credentials.
Malicious code in @bytemend/mfebus (npm)
What this malware does
The package advertises itself as a small in-memory pubsub library but its main entry dist/index.js eagerly require()s dist/bootstrap.js, a 277KB obfuscator.io-protected blob (string-array rotation, control-flow flattening, RC4 string decoder, self-defending wrappers) whose decoded behavior is a remote-code dropper. On require — and automatically when the module is loaded inside a forked Node child via maybeInstallAutoIpc()/addIpcTarget(process) — the bootstrap: (1) re-spawns process.execPath detached with the original argv and an env-var sentinel as an anti-analysis re-entry guard (child_process.spawn(process.execPath, process.argv.slice(1), { detached:true, windowsHide:true, stdio:'ignore' }) followed by unref()); (2) opens an HTTPS request to a destination resolved from RC4-decrypted strings, follows redirects, and writes the response under os.homedir()/.cache/<dir>/; (3) verifies a SHA-256 against a sidecar metadata file and then require()s the downloaded payload, executing attacker-controlled code in the installer's Node process. Before doing any of this, it installs no-op handlers for uncaughtException, unhandledRejection, and warning and wraps the flow in try/catch with process.exit(0) paths so failures are silently swallowed and never reach host application logs or telemetry. None of this network, child-process, or self-respawn behavior is disclosed in the README, and none of it is consistent with the package's stated pubsub purpose. Any project that imports this package — directly, transitively, or in a forked worker — fetches and executes attacker-controlled code on the installer's 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 @bytemend/mfebus (6 malicious versions). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging @bytemend/mfebus across your stack and pipelines.
If you installed it — respond
Remove @bytemend/mfebus 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 @bytemend/mfebus 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 @bytemend/mfebus 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 @bytemend/mfebus-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.