Which versions of logfmt-core are malicious?

The following npm versions of logfmt-core are flagged malicious: 3.5.2. Treat any of these as compromised.

How do I remediate logfmt-core if I installed it?

Remove logfmt-core 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.

I already installed logfmt-core — how do I know if it already compromised me?

If logfmt-core 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.

Is logfmt-core part of a known attack campaign?

Yes — logfmt-core is associated with the IN-MAL-2026-007464 campaign. Packages in the same campaign often share infrastructure and payloads, so check whether any related packages are also in your dependency tree.

How do I find logfmt-core across my projects, lockfiles, and CI pipelines?

Scan your lockfiles (package-lock.json, pnpm-lock.yaml, yarn.lock, requirements.txt, poetry.lock, etc.) and build artifacts for logfmt-core (version 3.5.2). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging logfmt-core across your stack and pipelines.

Malicious package

logfmt-corenpm

Malicious code in logfmt-core (npm) Remove it immediately and rotate any exposed credentials.

MAL-2026-6437

Immediate action

Remove the package, then rotate any secrets the build/runtime could reach.

npm uninstall logfmt-core

What this malware does

On npm install, scripts/install-check.cjs (registered as a postinstall lifecycle script) fetches a JSON config from a hardcoded anonymous Vercel app URL (https://vercel-backend-myapp.vercel.app/config/logfmt-sync.json), parses it to obtain a.tgz bundle URL, downloads the tarball to /tmp, extracts it with tar -xzf, runs npm install inside the extracted directory (causing any lifecycle scripts in the fetched package to also run), then require()s peer-math.js from the bundle and invokes syncSession(). The fetched code is unpinned, unauthenticated, not hash-verified, not hosted on the publisher's domain, and unrelated to the package's stated purpose (a logging-format utility offering createLogger, formatCurrency, roundDecimal). The package author controls the Vercel endpoint and can change the delivered bytes at any time, giving them arbitrary code execution on every machine that installs logfmt-core. Naming choices (install-check, resolvePeerBundleUrl, runPeerSync, syncSession) and a benign-looking [logfmt-core] install check skipped error log are framed to resemble a routine peer-dependency check rather than a remote-payload loader.

Malicious versions

1 flagged

3.5.2

Indicators of compromise (SHA-256)

bb22b2557674e7d616805d8a4086d69e02896be169b9e5d4d053eb3628ebe038

Detection & response playbook

Malicious package

Find it
Scan your lockfiles (package-lock.json, pnpm-lock.yaml, yarn.lock, requirements.txt, poetry.lock, etc.) and build artifacts for logfmt-core (version 3.5.2). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging logfmt-core across your stack and pipelines.
If you installed it — respond
Remove logfmt-core 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 logfmt-core 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 logfmt-core 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

No. logfmt-core on npm has been identified as a malicious package (version 3.5.2 flagged). It should be removed immediately — do not install or keep it in your dependency tree.

Campaign

IN-MAL-2026-007464

References

npmjs.com

Credits

Amazon Inspector · finder

Detect & block this

O3 blocks logfmt-core-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.

Malware detection Runtime egress monitoring