SAST vs SCA: What's the Difference?

Overview

SAST (Static Application Security Testing) and SCA (Software Composition Analysis) are two of the most important application security disciplines — and they are often confused because both analyze code without running it. The key distinction is whose code they analyze.

SAST analyzes code you wrote. SCA analyzes code you depend on. Both are necessary; neither is a substitute for the other.

What is SAST?

SAST tools analyze your application's source code, bytecode, or binary for security vulnerabilities without executing it. They trace data flows from user-controlled inputs (sources) to dangerous operations (sinks) — detecting injection vulnerabilities, authentication flaws, and insecure configurations in code your team wrote.

SAST is most effective at catching: SQL injection, XSS, SSRF, command injection, hardcoded secrets, and insecure cryptographic usage in your own code.

What is SCA?

SCA tools inventory every package in your application's dependency graph — direct and transitive — and compare those packages against vulnerability databases (NVD, OSV, GitHub Advisory Database). When a package version you depend on has a known CVE, SCA reports it.

SCA also covers license compliance — tracking what open source licenses your dependencies require and flagging license obligations that conflict with your business model.

Where They Overlap

Some vulnerabilities exist at the boundary between SAST and SCA:

• Unsafe usage of a vulnerable library API — a function in a library that is safe in most uses but dangerous in yours. SCA flags the version; SAST flags the usage pattern.
• Dependency confusion — a supply chain attack where your code "imports" a package. SAST may detect the import pattern; SCA detects the malicious package.

Using Both Together

SAST and SCA are complementary. The vast majority of modern application vulnerabilities fall into two categories: vulnerabilities in your code (SAST domain) and vulnerabilities in your dependencies (SCA domain). Running both is required for comprehensive coverage.

Connection to Autonomous Code Governance

Autonomous code governance integrates both SAST and SCA findings into a unified remediation pipeline. When SAST identifies a SQL injection in your code, Hydra generates a parameterized query fix. When SCA identifies a CVE in a dependency, Hydra generates an update PR. Both are handled continuously and autonomously — no manual triage required.