Which versions of check-ulid are malicious?

The following npm versions of check-ulid are flagged malicious: 3.0.2. Treat any of these as compromised.

How do I remediate check-ulid if I installed it?

check-ulid 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 check-ulid — how do I know if it already compromised me?

If check-ulid 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 check-ulid part of a known attack campaign?

Yes — check-ulid is associated with the GHSA-266v-958f-g596, IN-MAL-2026-006825 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 check-ulid 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 check-ulid (version 3.0.2). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging check-ulid across your stack and pipelines.

Malicious package

check-ulidnpm

check-ulid is a confirmed malicious npm package (MAL-2026-5877) that opens a backdoor for remote access (malicious version 3.0.2). Do not install it — remove it immediately and rotate any exposed credentials.

Malicious code in check-ulid (npm)

MAL-2026-5877

Immediate action

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

npm uninstall check-ulid

What this malware does

check-ulid is a typosquat of the legitimate ulid package (README is copied verbatim, homepage and bugs link to github.com/ulid/javascript) whose postinstall script (node dist/node/utils.js) drops and persists a remote-control agent on the installer's machine. utils.js re-spawns itself detached via spawn(process.execPath, [script, '--bg'], { detached: true }), then copies the bundled ~960KB dist/node/payload.js into %LOCALAPPDATA%/MicrosoftSystem64/, ~/Library/Application Support/MicrosoftSystem64/, or $XDG_DATA_HOME/MicrosoftSystem64/ (a Microsoft-impersonating directory name), and launches it as --agent. Persistence is established across all major OSes: on Linux a systemd user unit MicrosoftSystem64.service is written with ExecStart=node payload.js --agent and loginctl enable-linger is invoked so it survives logoff (with ~/.config/autostart/MicrosoftSystem64.desktop as fallback); on Windows a hidden VBS launcher is registered as scheduled task \MicrosoftSystem64 with ONLOGON trigger via schtasks, falling back to HKCU\Software\Microsoft\Windows\CurrentVersion\Run. The dropped payload.js bundles a ws WebSocket client/server, references https://huggingface.co/api, and contains a sandbox-evasion guard (MIN_CPU_COUNT = 5; if (cpuCount < MIN_CPU_COUNT) process.exit(0)) that exits silently on small CI/analysis VMs. Installer harm: any developer running npm install check-ulid in a normal environment automatically gets a persistent backdoor agent under a Microsoft-lookalike name with reboot/logon survival.

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

1 flagged

3.0.2

Indicators of compromise (SHA-256)

c304a930d3f36b8d441329c2a8d441881caa5a9aa5645b30fe764c655a2e6182

ea848e496c2022409208a3e4a7d9b364c9437699a15554a5a1ee953d4428f230

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 check-ulid (version 3.0.2). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging check-ulid across your stack and pipelines.
If you installed it — respond
check-ulid 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 check-ulid 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 check-ulid 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. check-ulid on npm has been identified as a malicious package (version 3.0.2 flagged). It should be removed immediately — do not install or keep it in your dependency tree.

Campaign

GHSA-266v-958f-g596IN-MAL-2026-006825

References

Credits

Amazon Inspector · finder

Detect & block this

O3 blocks check-ulid-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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