chai-as-bufferednpm
Advisory published Updated
chai-as-buffered is a confirmed malicious npm package (MAL-2026-10041) that opens a backdoor for remote access (malicious versions 3.7.24, 7.2.5). Do not install it — remove it immediately and rotate any exposed credentials.
Malicious code in chai-as-buffered (npm)
What this malware does
[email protected] is a typosquat lure (name resembles chai-as-promised; README and module exports impersonate the pino logger) whose actual behavior is a remote-payload dropper. lib/caller.js shadows process with a local object whose env holds base64-encoded constants for the C2 URL, header name, and header value, hiding the destination from review and from env scanning. When the exported middleware is invoked (e.g., via chai.use(...) or require('chai-as-buffered') wiring through the pino-styled export), the package base64-decodes the hidden URL (https://api.jsonstorage.net/v1/json/2ef8c758-a96f-459e-b036-b3b90379a165/a179ea35-b962-4722-b3f1-e28316d1a44a), spawns a detached, stdio-ignored node./lib/caller.js child, fetches a JSON document from that mutable third-party blob, and passes the document's cookie field to Function.constructor('require', s) invoked with the live require. The fetched JavaScript executes with full require access on the installer's machine. The destination is an attacker-controlled mutable JSON store whose content can be changed at any time, giving the publisher arbitrary code execution against any environment that loads this package.
Malicious versions
Indicators of compromise (SHA-256)
Detection & response playbook
Backdoor / remote accessFind it
Search your lockfiles and build artifacts for chai-as-buffered (2 malicious versions).
If you installed it — respond
chai-as-buffered 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 chai-as-buffered 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
- ReversingLabs · finder
Detect & block this
O3 blocks chai-as-buffered-class packages before install and in CI — and if it already ran, its runtime egress monitoring catches the C2 callback and severs the channel.