claims-ac1npm
Advisory published Updated
claims-ac1 is a confirmed malicious npm package (MAL-2026-18450) that opens a backdoor for remote access (malicious version 1.0.0). Do not install it — remove it immediately and rotate any exposed credentials.
Malicious code in claims-ac1 (npm)
What this malware does
claims-ac1 1.0.0 contains only a package.json declaring a single dependency, node-ac2, that is not fetched from the npm registry but from a tarball in the GitHub repository GamerD11/ping_test (https://github.com/GamerD11/ping_test/raw/main/node-ac2.tgz). That tarball has no code and in turn depends on node-ac3, another tarball in the same repository (https://github.com/GamerD11/ping_test/raw/main/node-ac3.tgz), whose preinstall script runs node index.js and silently ignores errors. The script reads a collector host name from https://raw.githubusercontent.com/GamerD11/ping_test/main/test.txt (an oastify.com host when observed) and does nothing if the file is empty; otherwise it sends an HTTPS POST to that host on port 443, path /health, with certificate verification disabled, containing the Node.js version, home directory, working directory, platform and architecture. The package has no legitimate functionality, the data is collected without the user's knowledge, and because the install-time code and the collector host live in a GitHub repository outside the npm package, the publisher can change them at any time without a new npm release. The same repository and mechanism are used by claims-acct-unlock (MAL-2026-18404) and dependencykfeg (MAL-2026-18416). Any machine that installed this version has disclosed the listed host details to a third party; remove the package.
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
Backdoor / remote accessFind it
Search your lockfiles and build artifacts for claims-ac1 (version 1.0.0).
If you installed it — respond
claims-ac1 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 claims-ac1 was installed, its post-install payload may already have run. Removing the package does not undo that — check outbound connections and credential use from the install window onward.
Frequently asked questions
Campaign
References
Credits
- Robin Frehner, Protet · finder
Detect & block this
O3 blocks claims-ac1-class packages before install and in CI — and if it already ran, its runtime egress monitoring catches the C2 callback and severs the channel.