MAL-2026-11988 Malicious code in tslint-folder-schema (npm)

npm/tslint-folder-schema is affected by the large-scale, self-propagating npm supply-chain worm of 2026-08-04 (the "Shai-Hulud: Here We Go Again" wave) — the same campaign that began with the compromise of the keyv and cacheable maintainer account. The listed version(s) were trojanized and republished by the worm after it reached an npm publish token belonging to a maintainer in this namespace; the payload enumerates every package a stolen token controls and republishes each with the same hook, so many packages under this scope were poisoned in the same short window. Every poisoned release adds a preinstall hook ("preinstall": "node setup.mjs") that runs on a bare npm install, before any project code. setup.mjs downloads a standalone Bun runtime and runs a byte-identical, heavily obfuscated ~728 KB second-stage credential stealer (shipped as Math_Symbol.js / math_init.js). It harvests GitHub, npm, AWS, GCP, Azure, HashiCorp Vault and Kubernetes credentials plus generic secrets and private keys (TruffleHog-style sweep), reads CI/CD secrets and identifies build runners, then republishes further packages the stolen token can reach. Rather than a fixed command-and-control host, it exfiltrates stolen findings to attacker-created GitHub repositories (descriptions reading "Shai-Hulud: Here We Go Again") and over DNS. Treat any environment that installed an affected version (with install scripts enabled) as compromised: rotate and revoke all reachable credentials (npm and GitHub tokens, cloud keys, Vault/Kubernetes secrets, and CI org/repo secrets). Part of the August 2026 npm worm that poisoned 400+ packages across many organizations.

[email protected] declares a preinstall hook (node setup.mjs) that runs automatically on npm install. setup.mjs downloads the Bun runtime binary from https://github.com/oven-sh/bun/releases/download/bun-v<ver>/..., extracts it to a temporary directory, chmod +x's it, and invokes it via execFileSync(bunPath, [<path to math_init.js>], {stdio:'inherit'}) to execute the shipped sibling file math_init.js. math_init.js is a 727KB heavily obfuscated blob (// @bun @bun-cjs header, string-array shuffle via WV8StW rotating a large mixed constant table, _0x-style identifier renaming) that is not referenced by the declared library entry lib/folderSchemaRule.js and only reachable through the preinstall→Bun path — the payload is designed to run under an alternate runtime so Node-based static analysis cannot reason about it. package.json also impersonates an unrelated organization: name is tslint-folder-schema but homepage and repository point at github.com/servicetitan/folder-lint, and the visible library code mirrors that project's tslint rule as cover. The alternate-runtime-dropper shape, opaque obfuscated payload, and metadata impersonation together are the install-time-RCE fingerprint: installing this package auto-executes attacker-controlled, non-inspectable code with the installer's privileges.

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.