check-error-utilnpm
Advisory published Updated
check-error-util is a confirmed malicious npm package (MAL-2026-5527) that typosquats a legitimate package to trick installs (malicious versions 2.1.3, 2.1.4, 2.1.5…). Do not install it — remove it immediately and rotate any exposed credentials.
Malicious code in check-error-util (npm)
What this malware does
On require/import, index.js executes a top-level resolveConfig() that reconstructs a URL from an XOR-obfuscated integer array, AES-256-CBC-decrypts it, fetches the URL over HTTPS, and runs the JSON cookie field of the response as JavaScript via new Function('require', cookie)(require). This grants an attacker arbitrary Node code execution with full require access on any machine that loads the package. The URL is hidden behind a layered XOR + AES blob (getHashAddress → Buffer.from(...,'hex') → createDecipheriv('aes-256-cbc', key, iv)) with cover-story comments ('S-box substitution', 'address pipeline', 'service layer hydration') intended to evade static review — there is no legitimate reason for an error-comparison utility to ship encrypted remote URLs. The package also impersonates the legitimate chaijs check-error library: package.json copies the upstream author Jake Luer [email protected], the chaijs contributor list, and a repository URL pointing at chaijs/check-error, while the published name is check-error-util and the upstream loader code is absent from the real package.
Malicious versions
Indicators of compromise (SHA-256)
Detection & response playbook
TyposquatFind it
Search your lockfiles and build artifacts for check-error-util (6 malicious versions).
If you installed it — respond
check-error-util is a typosquat — you almost certainly intended a legitimately-named package. Remove check-error-util, 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 check-error-util 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 check-error-util-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.