ts-biginteger-libnpm
Advisory published Updated
ts-biginteger-lib is a confirmed malicious npm package (MAL-2026-6316) that typosquats a legitimate package to trick installs (malicious version 5.0.5). Do not install it — remove it immediately and rotate any exposed credentials.
Malicious code in ts-biginteger-lib (npm)
What this malware does
Package is published as 'ts-biginteger-lib' but its metadata, README, and source are a wholesale copy of big.js by MikeMcl (author set to 'Michael Mclaughlin [email protected]', repository pointing at MikeMcl/big.js, README unchanged). Inserted into the otherwise-verbatim big.js source at big.js:605-609 is a try/catch that, at module load time, calls require("ts-lint-builders") and invokes doc.from_str().then(...).catch(...). package.json additionally declares "ts-linter-builders": "latest" as a runtime dependency. The legitimate big.js declares no runtime dependencies; these injected loads execute arbitrary code from separately-published, attacker-controlled packages every time a consumer require()s or imports ts-biginteger-lib. The unpinned latest specifier lets the publisher rotate the payload at any time without modifying this package. The combination of brand impersonation (to attract installers searching for a TypeScript big-integer library) and require-time execution of an external, version-floating dependency is a supply-chain dropper.
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
TyposquatFind it
Search your lockfiles and build artifacts for ts-biginteger-lib (version 5.0.5).
If you installed it — respond
ts-biginteger-lib is a typosquat — you almost certainly intended a legitimately-named package. Remove ts-biginteger-lib, install the correct package, and rotate any secrets exposed during the install since post-install scripts may have already run.
Did it already run?
If ts-biginteger-lib 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
- Amazon Inspector · finder
Detect & block this
O3 blocks ts-biginteger-lib-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.