Software supply chain attacks aren’t theoretical anymore–they’re operational risks. Because organizations rely on open source and third-party components, maintaining software supply chain integrity is a fundamental security requirement. But how do you secure the thousands of external components flowing into your development environment every day?

That’s exactly why the Secure Supply Chain Consumption Framework (S2C2F) framework exists.

S2C2F provides a practical, principles‑driven approach to strengthening trust specifically for the consumption of open source software (OSS). Unlike other frameworks that focus on how you build software (like SLSA), S2C2F focuses on how you ingest it.

In this post, we’ll break down the eight practices that comprise S2C2F, explain how they work together, and show how they help organizations consume open source software with confidence.

New to S2C2F? Before diving in, we recommend reading our previous post in the series:

👉 Understanding S2C2F: How It Strengthens OSS Security

What is the S2C2F framework?

At its core, S2C2F is a software supply chain integrity framework designed to reduce the risk of consuming malicious or vulnerable open source components. Originally developed by Microsoft and contributed to the OpenSSF, it shifts the focus from "secure coding" to "secure consumption."

The framework is built on a maturity model that helps organizations move from ad-hoc ingestion to a fully governed, secure supply chain.

Why S2C2F matters for supply chain integrity

Instead of vague promises about "security," S2C2F defines clear expectations for how external code enters your ecosystem. The S2C2F security principles focus on:

• Reducing the attack surface of external dependencies.
• Improving inventory visibility (knowing what you have).
• decreasing mean-time-to-remediate (MTTR) when vulnerabilities are found.

The 8 core principles of S2C2F

The S2C2F framework is organized into eight distinct areas of practice. Individually, they address specific consumption risks; collectively, they create a "defense in depth" strategy for your OSS supply chain security.

1. Ingest

Control the front door. The first and most critical practice is defining how open source packages enter your organization. Instead of allowing developers to pull directly from public registries (like npm or PyPI), which exposes you to typo-squatting and "dependency confusion" attacks, S2C2F mandates using a central artifact repository.

• Goal: Centralize and cache all external dependencies.
• Impact: Prevents "left-pad" incidents (deleted packages) and establishes a single control point for policy enforcement.

2. Inventory

You can't secure what you can't see. This practice focuses on maintaining a complete, accurate record of all third-party artifacts used across your organization. This goes beyond a simple list; it requires generating and managing a Software Bill of Materials (SBOM) for every application.

• Goal: Universal visibility into dependencies.
• Impact: When the next Log4j happens, you can instantly query where it is running in your stack.

3. Scan

Automate vulnerability detection. Ingested components must be scanned before they are used. S2C2F emphasizes scanning not just for known vulnerabilities (CVEs), but also for malware, license compliance, and heuristic risk signals.

• Goal: Stop bad packages before they reach the build server.
• Impact: Reduces technical debt by blocking high-risk components early in the lifecycle.

4. Update

Keep dependencies fresh. Software rot is a security risk. This practice ensures that your organization has a process for keeping dependencies up to date. Outdated packages are the number one vector for exploitation.

• Goal: Automate dependency updates (e.g., via bot PRs).
• Impact: Minimizes the "vulnerability window" that attackers can exploit.

5. Enforce

Governance as code. Explicitly define trust boundaries . The "Enforce" practice involves setting policies that automatically reject components that don't meet your security standards (e.g., blocking packages with critical CVEs or unacceptable licenses).

• Goal: Automated policy gates at the ingestion point.
• Impact: Prevents human error and ensures compliance with supply chain integrity principles.

6. Audit

Verify first, then trust. Every action in the supply chain–from ingestion to deployment–should be logged. This practice ensures that you can trace exactly who brought a package in, when it was scanned, and where it was used.

• Goal: immutable logging and traceability.
• Impact: Enables forensic investigation and proves compliance to auditors.

7. Rebuild

Advanced integrity verification. For organizations with high security requirements , trusting the binary isn't enough. This practice involves rebuilding open source packages from the source code on your own trusted infrastructure to verify that the distributed binary matches the source code.

• Goal: Verify artifact integrity independent of the upstream publisher.
• Impact: Mitigates sophisticated attacks where the upstream build system is compromised (like SolarWinds).

8. Fix & upstream

Contribute back to security. Security is a community effort. This practice encourages organizations to fix vulnerabilities they find in open source projects and, critically, contribute those fixes back to the upstream community.

• Goal: Patch locally, share globally.
• Impact: Strengthens the entire open source security framework and reduces the maintenance burden of carrying private patches.

How S2C2F strengthens OSS security

Taken together, these eight practices provide a structured way to understand, assess, and control risk in complex, dependency‑driven ecosystems.

For organizations that rely heavily on open source, the S2C2F framework answers the hard questions:

• Can we trust the artifacts we consume? (Yes, because we Ingest and Scan them.)
• Do we know where they are? (Yes, because we Inventory them.)
• Can we survive a compromise? (Yes, because we have Audit logs and Update paths.)

By addressing these questions directly, S2C2F becomes a practical secure software supply chain model, moving you from reactive patching to proactive governance. Using an artifact manager to apply and enforce these practices allows organizations to automate and incorporate security into development pipelines without creating extra work for developers.

FAQ: S2C2F principles explained

What is the S2C2F framework?

Secure Supply Chain Consumption Framework (S2C2F) is a security framework adopted by the OpenSSF that focuses on securing how organizations consume (ingest) open source software. It outlines eight core practices and four maturity levels to improve supply chain integrity.

2. What is the difference between S2C2F and SLSA?

S2C2F is for consumers (focusing on ingestion, scanning, and inventory of dependencies), while SLSA is for producers (focusing on the build integrity and provenance of the artifacts you create). They are complementary frameworks.

3. Why are S2C2F practices important for open source security?

Because most modern applications are 80-90% open source code, the supply chain is the largest attack surface. S2C2F provides a standardized way to vet and manage this code, preventing attacks like dependency confusion and malicious injection.

Continue the S2C2F Journey

Understanding the practices is only one step toward stronger supply chain integrity. Now, it's time to assess your maturity.

What to do next:

1. Download the guide: Software Supply Chain and Artifact Management Maturity Assessment
2. Audit your ingestion: Check if your developers are pulling directly from public repositories, like npm and Maven, or using a secure proxy.
3. Explore Cloudsmith: See how our platform automates the Ingest, Scan, and Enforce pillars of S2C2F today.