Detecting Dependency Confusion

Legal Notice: This skill is for authorized security testing, defensive engineering, and educational purposes only. Registering or claiming package namespaces you do not own, or testing build pipelines without written authorization, may be illegal and may violate the terms of service of public registries. Only run namespace-claiming or resolution-testing activities against names and infrastructure you control or are explicitly authorized to assess.

Overview

Dependency confusion (also called a substitution or namespace-shadowing attack) was popularized by Alex Birsan in 2021 when he forced malicious code into the internal build systems of Apple, Microsoft, PayPal, and dozens of others. The root cause is that many package managers, when configured to resolve from both an internal/private registry and a public one, will prefer whichever copy has the higher version number rather than honoring the source. An attacker who learns the name of a private package (@acme/internal-utils, acme-billing-sdk) can publish a malicious package of the same name to the public registry (npmjs.com, PyPI, Maven Central) with a very high version (e.g. …