MalwarePublished 24 Sep 2026Updated 30 Sep 2026

building-build (npm) · Malicious Code

Affects building-buildSource GCVE Database

Malicious package : remove building-build and rotate any secrets on hosts that installed it.

Data as of 30 Sep 2026, 16:37 UTC

Classification

Malicious package

Published to npm · OSV MAL-2026-17164

What to do

Remove building-build 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
npmbuilding-build	Affected =1.0.0	Fixed in–

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Description

The npm package 'building-build' version 1.0.0 contains malicious code that, when loaded, schedules a timer to fetch sensitive privileged same-origin paths and posts their contents to a site endpoint. The package masquerades as a benign library but exists solely to exfiltrate data accessible via the authenticated user's session. Installation of this package compromises the host system, potentially exposing all stored secrets and keys.

Impact

Any system with this package installed or running is considered fully compromised. The malicious code can exfiltrate sensitive privileged data accessible via the user's session, potentially exposing secrets and keys stored on the computer. Because the package abuses the authenticated user's session to access privileged paths, it can lead to unauthorized data disclosure. Removal of the package alone may not fully remediate the compromise, as the attacker may have established further persistence or control.

Defensive guidance

Immediate removal of the 'building-build' package version 1.0.0 is required. All secrets and keys stored on the compromised system should be rotated immediately from a different, trusted computer. Due to the high likelihood of full system compromise, a thorough incident response and system rebuild may be necessary.

Summary

The 'building-build' npm package (version 1.0.0) includes a single index.js file that, upon loading, periodically fetches a hardcoded list of privileged same-origin paths such as /admin, /dashboard, /flag, /api/flag, /secret, and /admin/flag. It then sends the response bodies of these requests as JSON payloads to the /addPost endpoint, leveraging the ambient session of the authenticated user running the bundle. The package's metadata is minimal and misleading, with no exports and unrelated naming, indicating it is designed solely to deliver this malicious payload. This behavior effectively allows an attacker to read and exfiltrate privileged data from the victim's web application context.

References

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What to do

Affected software

Description

AI analysisMachine-generated, updated 30 Sep 2026, 16:37 UTC

Technical details

References

Community reviews