What is SCA?

What SCA actually does

Software Composition Analysis finds known vulnerabilities in the open-source libraries your application depends on. It does not scan your code. It scans your dependencies.

Modern applications are mostly open source. The Synopsys 2024 OSSRA report found 96% of commercial codebases contain open-source components, and 84% of those have at least one known vulnerability. The average application pulls in over 500 open-source dependencies.

You can write the most secure code in the world, but if you import a library with a critical vulnerability, you inherit that risk.

SCA tools read your manifest files (package.json, pom.xml, requirements.txt, go.mod, Gemfile.lock), identify every direct and transitive dependency, and cross-reference them against vulnerability databases like the National Vulnerability Database (NVD), OSV, and vendor-curated databases.

The tool runs in seconds. It tells you which dependencies have known CVEs, how severe they are, and in many cases, which version to upgrade to.

SCA also handles license compliance. Open source does not always mean “free to use however you want.” A copyleft license like GPL can require you to open-source your own code. If you ship commercial software, SCA catches licensing conflicts before they become legal problems.

How SCA works

SCA follows a simpler pipeline than SAST or DAST. Identify dependencies, check them against databases, report what you find.

Dependency discovery

The tool scans your manifest files and lock files to build a complete dependency tree: direct dependencies (what you explicitly installed) and transitive dependencies (what your dependencies depend on). A typical Node.js project with 20 direct dependencies might have 200+ transitive dependencies.

Some tools also scan compiled binaries and container images to identify components not in manifest files. Black Duck is particularly strong at binary analysis.

Vulnerability matching

Each component and version is checked against vulnerability databases. OWASP Dependency-Check uses NVD directly. Commercial tools like Snyk and Mend maintain their own curated databases that update faster. The speed difference matters: NVD can take weeks to publish a new CVE, while vendor databases often pick it up within hours.

Reachability analysis

This is what separates basic SCA from actually useful SCA. A dependency might have a vulnerability in a function your application never calls. Traditional tools report it anyway, and the noise piles up.

Reachability analysis checks whether the vulnerable code path is actually reachable from your application. Endor Labs and Contrast SCA do this through static call graph analysis. Qwiet AI uses code property graphs. The result is typically a 70-90% reduction in alerts, which makes a huge difference for developer adoption.

License compliance

SCA tools check the licenses of every dependency against your organization’s policies. Common license types:

• MIT, Apache 2.0, BSD — Permissive. Generally safe for commercial use.
• GPL, AGPL — Copyleft. Can require you to open-source your own code if you distribute software.
• LGPL — Weak copyleft. Typically okay for dynamic linking in commercial software.

FOSSA and Black Duck are the strongest tools for license compliance. Snyk covers it too, but with less depth on complex licensing scenarios.

SBOM generation

Most SCA tools can produce a Software Bill of Materials in CycloneDX or SPDX format. The US Executive Order on Cybersecurity (2021) mandates SBOMs for software sold to federal agencies, and adoption is growing beyond government. Even if compliance is not your concern today, having an SBOM makes it much faster to check whether you are affected when the next Log4Shell drops.

What SCA catches

SCA focuses on a specific attack surface:

• Known vulnerabilities (CVEs) — The core function. If a dependency version has a published CVE, SCA flags it.
• License violations — Dependencies with licenses that conflict with your organization’s policies or commercial distribution model.
• Outdated dependencies — Components that are several versions behind, which may indicate unmaintained or abandoned libraries.
• Malicious packages — Newer tools like Socket analyze package behavior to detect typosquatting, dependency confusion, and other supply chain attack patterns.

The noise problem

The biggest complaint about SCA is alert volume. A typical enterprise application might show hundreds of vulnerable dependencies, most of which are transitive (dependencies of dependencies) and many of which are not exploitable in context.

I have seen teams disable SCA alerts entirely because the noise was unbearable. That is worse than having no SCA at all, because it creates a false sense of coverage.

Three things help.

Reachability analysis. Endor Labs and Contrast SCA cut alerts by 70-90% by showing which vulnerabilities are actually reachable from your code. The most effective noise reduction available.

Severity filtering. Not every CVE is critical. Block merges on critical and high, warn on medium, suppress low. Most tools support this.

Transitive dependency focus. A vulnerability in a direct dependency you control is more actionable than one buried three levels deep. Some tools let you prioritize accordingly.

Supply chain attacks

Traditional SCA checks dependencies against databases of known vulnerabilities. That works for CVEs that have already been reported. Supply chain attacks are a different problem.

An attacker compromises a legitimate package or publishes a malicious one that looks legitimate. There is no CVE because nobody has reported it yet. Traditional SCA misses these entirely.

The numbers are ugly. The Sonatype 2024 State of the Software Supply Chain report found a 156% year-over-year increase in malicious packages, with over 704,102 malicious packages identified since 2019 across npm, PyPI, and other ecosystems.

Socket takes a different approach to this problem. Instead of matching against CVE databases, it analyzes what packages actually do: network calls, filesystem access, obfuscated code, install scripts. If a package that is supposed to be a string formatting library suddenly starts making HTTP requests to an unknown server, Socket flags it.

Checkmarx SCA has a similar behavioral analysis feature that evaluates package provider credibility, update cadence, and runtime behavior.

For teams worried about supply chain risk, the combination of traditional SCA (for known CVEs) and behavioral analysis (for unknown threats) provides the broadest coverage.

SBOMs and compliance

A Software Bill of Materials is an inventory of every component in your software. If you sell a food product, you list the ingredients. An SBOM does the same for software.

The push for SBOMs accelerated after the US Executive Order on Cybersecurity in 2021, which requires SBOMs for software sold to federal agencies. The EU Cyber Resilience Act has similar requirements coming.

SBOMs are useful beyond compliance. When Log4Shell (CVE-2021-44228) was disclosed in December 2021, organizations with SBOMs could immediately check whether they were affected. Everyone else spent days or weeks manually inventorying their dependencies.

Standard formats:

• CycloneDX — OWASP-maintained, lightweight, widely supported.
• SPDX — Linux Foundation-maintained, ISO standard, more detailed.

Most SCA tools generate SBOMs in both formats. Black Duck, Snyk, and Endor Labs all include SBOM generation.

SCA vs SAST

SCA and SAST are often confused because both run before deployment. They look at completely different things.

You want both. SCA checks what you imported. SAST checks what you wrote. Together they cover the full picture of what goes into production.

For a broader comparison that includes DAST and IAST, see our SAST vs DAST vs IAST guide.

Top SCA tools

These are the tools I would look at first. For full reviews and comparisons, see the SCA tools page.

Free and open-source

• OWASP Dependency-Check — The only fully open-source SCA tool. Uses NVD database. Multi-platform. A solid starting point for teams with zero budget.

Freemium (free tier + paid plans)

• Snyk Open Source — Auto-remediation PRs, IDE integration, SBOM generation. The easiest tool to get started with.
• FOSSA — Strongest option for license compliance. Used by companies like Uber and Verizon.
• Socket — Supply chain attack detection through behavioral analysis. Free for open-source projects.
• JFrog Xray — Works well if you already use JFrog Artifactory for artifact management.

Commercial

• Black Duck — SBOM generation and license compliance. The strongest binary analysis in the market. Now independent after the Synopsys split.
• Endor Labs — Reachability analysis that cuts alert volume dramatically. Newer entrant, but growing fast.
• Mend SCA — Auto-remediation and strong CI/CD integration. Formerly WhiteSource.
• Checkmarx SCA — Part of Checkmarx One platform. Supply chain behavioral analysis included.

Getting started

SCA is probably the easiest security tool category to adopt. Here is a practical path.

Start with a free tool. Snyk Open Source has the smoothest onboarding. Run snyk test in your project directory and you have results in seconds. OWASP Dependency-Check is the fully free alternative.

Review the initial findings. Your first scan will probably show dozens of vulnerable dependencies. Do not panic. Sort by severity, focus on critical and high first, check whether the affected library is actually used in a way that exposes the vulnerability.

Update what you can. Many findings are fixed by bumping a dependency version. Snyk and Mend can open auto-remediation PRs. Review the updates before merging since version bumps can introduce breaking changes.

Add it to CI. Run the tool on every pull request. Block merges on critical vulnerabilities. Warn on high and medium.

Set up license policies. Define which licenses your organization allows. Block any dependency with a copyleft license if you ship commercial software.

Consider SBOM generation. Add it to your release pipeline. Costs nothing and gives you an inventory you can query when the next Log4Shell drops.

FAQ

Frequently Asked Questions

Written by

Suphi Cankurt

Suphi Cankurt is an application security enthusiast based in Helsinki, Finland. He reviews and compares 129 AppSec tools across 10 categories on AppSec Santa. Learn more.