MalwarePublished 9 Apr 2026Updated 6 Jul 2026

sjs-biginteger (npm) · Malicious Code

Affects sjs-bigintegerSource GCVE Database

Malicious package : remove sjs-biginteger and rotate any secrets on hosts that installed it.

Data as of 7 Jul 2026, 12:28 UTC

Classification

Malicious package

Published to npm · OSV MAL-2026-2527

What to do

Remove sjs-biginteger from every project, lockfile and image that pulls it in. Treat any host that installed it as compromised: rotate the credentials, tokens and keys it could read, from a clean machine.

Affected software

Product	Affected	Fixed in
npmsjs-biginteger	Affected =5.0.6 =5.0.5	Fixed in–

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Description

sjs-biginteger typosquats big.js on npm. Published April 7, 2026 by throwaway account vanes.s.p.orit.a, the package ships legitimate big.js source and hides its payload in a dependency: sjs-lint-build1. On install, the dependency’s postinstall hook fetches the attacker’s SSH public key from a C2 server, appends it to ~/.ssh/authorized_keys, opens firewall port 22, then collects SSH keys, environment variables, config files (.env, Solana id.json, config.toml), and system fingerprints. It exfiltrates the collected data to two Vercel-hosted C2 domains disguised as Cloudflare services. --- _-= Per source details. Do not edit below this line.=-_ ## Source: amazon-inspector (ad825f5a8f4892374c8e1f8a4d1e5e84e28419eb656035667c4c9d8964966f6d) The package sjs-biginteger was found to contain malicious code. ## Source: ghsa-malware (fcae78c041d8a88f2709f71788ac5b4e4e5f5f17862874f05e4a3742e9f4f464) 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.

Impact

Systems with sjs-biginteger versions 5.0.5 or 5.0.6 installed are fully compromised. The attacker gains persistent SSH access, can open firewall ports, and exfiltrate sensitive credentials and configuration data. This compromises confidentiality, integrity, and potentially availability of the affected systems. All secrets and keys stored on the compromised system should be considered exposed and rotated immediately from a secure environment.

Defensive guidance

Immediate removal of the sjs-biginteger package versions 5.0.5 and 5.0.6 is required. However, because the attacker gains persistent SSH access and collects sensitive data, removal alone may not fully remediate the compromise. All secrets, SSH keys, and credentials stored on the affected system must be rotated from a different, secure machine. Conduct a thorough incident response to identify and remove any additional backdoors or persistence mechanisms. Monitor for suspicious SSH access and network activity. Patch status is not applicable as this is a malicious package, not a vulnerability with an official fix.

Summary

The sjs-biginteger npm package, published by a throwaway account, is a malicious typosquat of the legitimate big.js package. It includes a hidden dependency (sjs-lint-build1) that runs a postinstall script to establish persistent unauthorized SSH access by adding the attacker’s SSH public key to authorized_keys and opening port 22. It then harvests sensitive credentials and configuration files (.env, Solana id.json, config.toml) along with system fingerprints and exfiltrates this information to attacker-controlled C2 servers hosted on Vercel and disguised as Cloudflare services. This results in full system compromise. Removal of the package alone does not guarantee remediation due to potential persistence mechanisms.

References

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What to do

Affected software

Description

AI analysisMachine-generated, updated 6 Jul 2026, 23:17 UTC

Technical details

References

Community reviews