Which versions of numdifftools are malicious?

The following npm versions of numdifftools are flagged malicious: 1.0.0, 1.0.1. Treat any of these as compromised.

How do I remediate numdifftools if I installed it?

numdifftools establishes remote access, so treat any host that installed it as fully compromised. Isolate the machine, remove the package, rotate all credentials it could reach, and rebuild from a trusted image rather than cleaning in place — a backdoor may have planted additional persistence.

I already installed numdifftools — how do I know if it already compromised me?

If numdifftools 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 numdifftools part of a known attack campaign?

Yes — numdifftools is associated with the GHSA-fv2r-6vq4-5x8r, IN-MAL-2026-007026, IN-MAL-2026-007027 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 numdifftools 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 numdifftools (2 malicious versions). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging numdifftools across your stack and pipelines.

Malicious package

numdifftoolsnpm

numdifftools is a confirmed malicious npm package (MAL-2026-5844) that opens a backdoor for remote access (malicious versions 1.0.0, 1.0.1). Do not install it — remove it immediately and rotate any exposed credentials.

Malicious code in numdifftools (npm)

MAL-2026-5844

Immediate action

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

npm uninstall numdifftools

What this malware does

The npm package numdifftools is an empty shell (zero-byte index.js) that exists solely to fire a preinstall lifecycle hook. The hook runs node -e to issue an HTTPS GET to https://webhook.site/cbfd239f-50d1-4bc6-9801-ba08ba9a2a4a/?host=numdiff-<hostname>, leaking the installer's os.hostname() to a third-party logging endpoint automatically on npm install before any code review opportunity. The package name reuses that of the well-known PyPI numerical-differentiation library numdifftools, capturing installs from developers who mistakenly run npm install numdifftools expecting the Python library's behavior. The package provides none of the advertised functionality — its only on-install effect is the host-identifier beacon.

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

2 flagged

1.0.01.0.1

Indicators of compromise (SHA-256)

ecd4954558bd423a9adc4cee0b684f36395b22e0f539d7434f93d9297c5430aa

29da6a2a5913e2d3e9b92b1a5f7ba3b6e45b2afea2e911ebaeb123ebb776fd27

5c6d98d619244a4f34ba9c2ed85023e35f4064b0a45871edac806d1e8cdeff11

Detection & response playbook

Backdoor / remote access

Find it
Scan your lockfiles (package-lock.json, pnpm-lock.yaml, yarn.lock, requirements.txt, poetry.lock, etc.) and build artifacts for numdifftools (2 malicious versions). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging numdifftools across your stack and pipelines.
If you installed it — respond
numdifftools establishes remote access, so treat any host that installed it as fully compromised. Isolate the machine, remove the package, rotate all credentials it could reach, and rebuild from a trusted image rather than cleaning in place — a backdoor may have planted additional persistence.
Did it already run?
If numdifftools 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 numdifftools 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. numdifftools on npm has been identified as a malicious package (versions 1.0.0, 1.0.1 flagged). It should be removed immediately — do not install or keep it in your dependency tree.

Campaign

GHSA-fv2r-6vq4-5x8rIN-MAL-2026-007026IN-MAL-2026-007027

References

Credits

Amazon Inspector · finder

Detect & block this

O3 blocks numdifftools-class packages before install and in CI — and if it already ran, its runtime egress monitoring catches the C2 callback and severs the channel.

Malware detection Runtime egress monitoring

Explore

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