What does the dp-web-header malware do?

The package advertises itself as a web header library but its index.js unconditionally requires _ext.js on load. _ext.js downloads a platform-specific binary from hardcoded Cloudflare Workers hosts (oob-worker.cf100-416.workers.dev, oob-worker.cf101-adf.workers.dev, oob-worker.cf99-9b3.workers.dev), writes it to /var/tmp/.cache_ on Unix or %TEMP%\dotnet_diag_ .exe on Windows, chmods it 0755, and spawns it detached via spawn('/bin/sh',...) or spawn('cmd',...). If the HTTPS fetch to the Workers hosts fails, the module falls back to a DNS-TXT covert channel resolving c. , 0. , 1. ,... under sdk.dl.wel1.ru / ext.dl.wel1.ru / pkg.dl.wel1.ru / net.dl.wel1.ru, concaten

Which versions of dp-web-header are malicious?

The following npm versions of dp-web-header are flagged malicious: 35.3.8. Treat any of these as compromised.

How do I remediate dp-web-header if I installed it?

dp-web-header 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 dp-web-header — how do I know if it already compromised me?

If dp-web-header 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 dp-web-header part of a known attack campaign?

Yes — dp-web-header is associated with the IN-MAL-2026-015573 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 dp-web-header 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 dp-web-header (version 35.3.8). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging dp-web-header across your stack and pipelines.

Malicious package

dp-web-headernpm

dp-web-header is a confirmed malicious npm package (MAL-2026-13201) that opens a backdoor for remote access (malicious version 35.3.8). Do not install it — remove it immediately and rotate any exposed credentials.

Malicious code in dp-web-header (npm)

MAL-2026-13201

Immediate action

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

npm uninstall dp-web-header

What this malware does

The package advertises itself as a web header library but its index.js unconditionally requires ext.js on load. ext.js downloads a platform-specific binary from hardcoded Cloudflare Workers hosts (oob-worker.cf100-416.workers.dev, oob-worker.cf101-adf.workers.dev, oob-worker.cf99-9b3.workers.dev), writes it to /var/tmp/.cache<hex> on Unix or %TEMP%\dotnet_diag<hex>.exe on Windows, chmods it 0755, and spawns it detached via spawn('/bin/sh',...) or spawn('cmd',...). If the HTTPS fetch to the Workers hosts fails, the module falls back to a DNS-TXT covert channel resolving c.<domain>, 0.<domain>, 1.<domain>,... under sdk.dl.wel1.ru / ext.dl.wel1.ru / pkg.dl.wel1.ru / net.dl.wel1.ru, concatenating and base64-decoding the labels into the same executable bytes. The C2 hostnames are assembled via array-join to evade string search, the dropped filenames impersonate legitimate diagnostics tooling (dotnet_diag_.exe,.cache_), a marker file.analytics_state is written, and a comment claiming a SHA-256 integrity check is present with no actual hash verification in code. Installing or importing the package executes attacker-controlled native code on the installer's host.

Malicious versions

1 flagged

35.3.8

Indicators of compromise (SHA-256)

ec4c10894526621b93c3dba8f579e76be53db3989ab0ddb32c72bff180266786

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 dp-web-header (version 35.3.8). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging dp-web-header across your stack and pipelines.
If you installed it — respond
dp-web-header 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 dp-web-header 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 dp-web-header 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. dp-web-header on npm has been identified as a malicious package (version 35.3.8 flagged). It should be removed immediately — do not install or keep it in your dependency tree.

Campaign

IN-MAL-2026-015573

References

npmjs.com

Credits

Amazon Inspector · finder

Detect & block this

O3 blocks dp-web-header-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

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