Software Supply Chain Failures — OWASP A03:2025

Overview

A03:2025 is the #1 community-voted concern and the highest-risk category by exploit score in the entire OWASP Top 10:2025, despite having only 6 CWEs and limited test data:

Key CWEs:

• CWE-1104 — Use of Unmaintained Third-Party Components
• CWE-1395 — Dependency on Vulnerable Third-Party Component
• CWE-1329 — Reliance on Component That is Not Updateable

What This Category Covers

Supply chain failures span the full lifecycle — from sourcing packages to building, distributing, and deploying them:

1. Untracked / unmonitored dependencies — direct and transitive
2. Vulnerable or unsupported components — unpatched known CVEs
3. Absence of SBOM management — no Software Bill of Materials
4. Unhardened CI/CD pipelines — no separation of duty, unsigned builds
5. Untrusted or typosquatted package sources
6. Delayed or absent patching cadence
7. Build system compromise (e.g. SolarWinds 2019, Log4Shell 2021, npm worms)

Python-specific surface: Flask alone pulls 7+ transitive packages (Jinja2, Werkzeug,
MarkupSafe, itsdangerous, click, blinker, packaging). FastAPI pulls Starlette + Pydantic +
their dependencies. Every transitive package is an attack surface.

Detecting Vulnerabilities — Tool Runbook

1. pip-audit (recommended — scans against OSV + PyPI Advisory DB)

# Install
pip install pip-audit

# Scan current environment
pip-audit

# Scan a requirements file
pip-audit -r requirements.txt

# Output JSON for CI
pip-audit -r requirements.txt -f json -o audit-results.json

# Fix automatically where possible
pip-audit --fix

2. safety (scans against Safety DB / PyUp)

pip install safety

# Basic scan
safety check

# Scan requirements file
safety check -r requirements.txt

# Full JSON output
safety check --json

3. osv-scanner (Google OSV — broadest database)

# Install via Go or download binary
go install github.com/google/osv-scanner/cmd/osv-scanner@latest

# Scan a project directory
osv-scanner --lockfile=requirements.txt .

4. Trivy (containers + filesystem)

# Scan Python project
trivy fs --scanners vuln .

# Scan a Docker image
trivy image myapp:latest

CI/CD Integration: Run pip-audit + safety on every PR. Fail the build on HIGH/CRITICAL
severity findings. See references/ci-cd-templates.md for GitHub Actions and GitLab CI examples.

Generating & Managing SBOMs

An SBOM (Software Bill of Materials) is now a compliance requirement (US Executive Order 14028) and an operational necessity.

Using cyclonedx-py

pip install cyclonedx-bom

# Generate CycloneDX SBOM from current environment
cyclonedx-py environment -o sbom.json --format json

# From a requirements file
cyclonedx-py requirements requirements.txt -o sbom.json --format json

# From poetry
cyclonedx-py poetry -o sbom.json

Using pip-licenses for license compliance

pip install pip-licenses
pip-licenses --format=json --output-file=licenses.json

SBOM should include:

• Package name + version + hashes
• License identifiers
• Known vulnerabilities at time of generation
• Transitive dependency tree

Hash Pinning & Lockfiles

Hash Pinning in requirements.txt

# BAD — unpinned, vulnerable to substitution attacks
flask==3.0.0

# GOOD — hash-pinned, tamper-evident
flask==3.0.0 \
    --hash=sha256:34a14a9e9ea... \
    --hash=sha256:a9b5cf1a...

Generate hash-pinned requirements:

pip install pip-tools
pip-compile --generate-hashes requirements.in -o requirements.txt

Lockfiles (preferred for applications)

Critical checks:

• Lockfile is committed to source control
• CI installs from lockfile, not loose requirements.txt
• Lockfile is regenerated on a schedule (weekly minimum)
• Dependabot / Renovate Bot is configured for automated PRs

Transitive Dependency Auditing

Visualize the full dependency tree

pip install pipdeptree
pipdeptree --json-tree > deptree.json

# Find who requires a specific package
pipdeptree --reverse --packages flask

Check for known malicious packages

# guarddog — detects malicious behavior in packages
pip install guarddog
guarddog pypi scan flask
guarddog pypi verify flask 3.0.0

Flag dangerous import patterns in source code

# Bandit catches these automatically:
import sys
sys.path.insert(0, '/untrusted/path')  # CWE-426: Untrusted Search Path
sys.path.append('/local/unverified')   # Same risk

bandit -r . -t B322,B323,B411  # sys.path manipulation checks

CI/CD Pipeline Hardening

Unhardened pipelines are a primary supply chain vector (SolarWinds attack model).

Minimum pipeline security requirements

GitHub Actions — pin by commit SHA

# BAD — tag can be moved by attacker
- uses: actions/checkout@v4

# GOOD — immutable SHA
- uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683

SLSA Framework compliance levels

• SLSA Level 1: Build process documented, basic provenance
• SLSA Level 2: Build service generates signed provenance
• SLSA Level 3: Hardened build platform, non-falsifiable provenance

# Generate SLSA provenance with slsa-verifier
pip install slsa-verifier
slsa-verifier verify-artifact mypackage.tar.gz \
  --provenance-path provenance.json \
  --source-uri github.com/myorg/myrepo

FastAPI & Flask — Specific Testing Targets

Dependency files to audit

Static analysis with Bandit

pip install bandit

# Full scan with supply-chain relevant rules
bandit -r . -t B301,B302,B303,B324,B411,B412 --format json -o bandit-report.json

Key Bandit rules for supply chain:

• B301 — pickle usage (deserialization risk)
• B302 — marshal (similar risk)
• B411 — xmlrpc imports
• B412 — httpoxy detection

Check for typosquatted / suspicious packages

# Use pip-audit with strict mode
pip-audit --strict -r requirements.txt

# guarddog behavior analysis
guarddog pypi scan <package>

Remediation Priority Matrix

Quick-Start Checklist

[ ] pip-audit and safety check passing in CI (no HIGH/CRITICAL)
[ ] All dependencies pinned in lockfile (poetry.lock / uv.lock)
[ ] Lockfile committed to source control and used in CI installs
[ ] SBOM generated (cyclonedx-py) and stored as CI artifact
[ ] Dependabot or Renovate Bot enabled on repository
[ ] GitHub Actions pinned by commit SHA
[ ] No sys.path.insert() / sys.path.append() on unverified paths
[ ] SLSA Level 2+ for published packages
[ ] Weekly lockfile refresh scheduled

Reference Files

• references/ci-cd-templates.md — GitHub Actions + GitLab CI pipeline templates with

pip-audit, safety, SBOM generation, and SLSA provenance steps

• references/cwe-mapping.md — Full CWE-to-detection-tool mapping for audit reporting