runtimekitnpm
runtimekit is a confirmed malicious npm package (MAL-2026-6477) that executes malicious code on install (malicious versions 1.0.1, 1.0.2, 1.0.3…). Do not install it — remove it immediately and rotate any exposed credentials.
Malicious code in runtimekit (npm)
What this malware does
lib/index.cjs and lib/index.mjs (re-required from lib/readonly.cjs) contain a self-executing IIFE that decodes two opaque strings via a custom shuffle routine (YWG), recovers the identifier constructor from one of them, retrieves the Function constructor via property access, then builds and invokes nested Function-constructor calls — Function('', Function('', decoded1))(decoded2)(7942) — executing arbitrary decoded JavaScript at module load. Before the synthesis, the loader assigns global.r = require and global.m = module, deliberately smuggling Node's require and module bindings into the global scope so the dynamically constructed function (which does not inherit the module's closure) can reach them. A marker global._V = "A6-Shadow-16" is also set. The package advertises itself as a validation/runtime utility but ships an obfuscated self-injecting loader with no legitimate purpose for hiding code from Function constructors. Any consumer that does require('runtimekit') or require('runtimekit/readonly') runs the decoded payload in-process with full Node privileges.
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 runtimekit (5 malicious versions). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging runtimekit across your stack and pipelines.
If you installed it — respond
Remove runtimekit 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 runtimekit 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 runtimekit 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 runtimekit-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.