dotnet-runtime-basenpm
dotnet-runtime-base is a confirmed malicious npm package (MAL-2026-10217) that executes malicious code on install (malicious versions 1.0.4, 1.0.5). Do not install it — remove it immediately and rotate any exposed credentials.
Malicious code in dotnet-runtime-base (npm)
What this malware does
The package's postinstall lifecycle script (package.json line 7: "postinstall": "node install.js") runs install.js, which on Windows writes a PowerShell script to %TEMP% and uses WebClient.DownloadFile to fetch https://raw.githubusercontent.com/cphc811-ui/d3d/main/npm-sc-legit.exe from a personal GitHub account unrelated to the package publisher, then launches the executable via powershell.exe with -WindowStyle Hidden -ExecutionPolicy Bypass -NoProfile -NonInteractive. The dropper is gated to skip when process.platform is not 'win32' and when NODE_ENV=='development', evading developer and CI environments. The fetch targets a mutable branch (main) with no hash or signature verification, the binary is staged to a temp path and started hidden, and index.js contains a cover-story comment labelling the postinstall as the hidden payload. Installing this package on Windows causes arbitrary attacker-controlled code to run 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 dotnet-runtime-base (2 malicious versions). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging dotnet-runtime-base across your stack and pipelines.
If you installed it — respond
Remove dotnet-runtime-base 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 dotnet-runtime-base 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 dotnet-runtime-base 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 dotnet-runtime-base-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.