What Is SAST? Static Application Security Testing Explained

SAST (Static Application Security Testing) is a category of security testing that analyzes application source code, bytecode, or binaries for vulnerabilities without executing the program. SAST is the security-focused application of static analysis—specifically targeting vulnerability classes like injection, cryptographic failures, and access control weaknesses.

SAST tools sit in the "shift left" category of application security, meaning they operate as early as possible in the software development lifecycle. While penetration testing and DAST (Dynamic Application Security Testing) require a deployed application, SAST works on source code the moment it is committed, making it the first automated security gate in a development pipeline.

The core value of SAST is coverage at scale. A human code reviewer might spend 30 minutes reviewing a 500-line pull request and still miss a subtle injection pattern buried in error handling logic. A SAST tool analyzes the same code in seconds, checking every line against hundreds of vulnerability patterns simultaneously.

SAST is a mandatory requirement in multiple compliance frameworks. PCI-DSS requires automated code review or static analysis for applications that handle payment data. Many SOC 2 and ISO 27001 audits expect evidence of automated security testing in the CI/CD pipeline.

SAST tools work by modeling code behavior without executing it. The process follows a consistent pattern across tools and languages:

1. Code Ingestion

The tool reads source files, resolves imports and module boundaries, and identifies the languages and frameworks in use. Multi-language repositories require analyzers for each language present.

2. Vulnerability Rule Matching

Each SAST tool ships with a rule set defining vulnerability patterns. Rules map to CWE identifiers and target specific code constructs:

// Rule: CWE-78 OS Command Injection
// Matches: child_process calls with unsanitized input
const { exec } = require('child_process');
exec('ls ' + userInput);  // Flagged: user input in command string

// Rule: CWE-327 Weak Cryptography
const hash = crypto.createHash('md5');  // Flagged: deprecated algorithm

3. Triage and Reporting

Findings are assigned severity scores (typically CVSS), mapped to CWE identifiers, and presented with file locations and remediation guidance. Teams triage findings by severity and reachability—a Critical finding in a request handler is more urgent than the same pattern in an unused utility function.

4. Integration

SAST tools integrate into the development workflow at multiple points: IDE plugins for real-time feedback, pre-commit hooks for local gatekeeping, CI/CD pipelines for PR checks, and scheduled scans for comprehensive repository audits.

Organizations that adopt SAST consistently find vulnerabilities earlier and reduce remediation costs. The opposite—discovering vulnerabilities in production—has proven catastrophic:

• SolarWinds (2020): Malicious code inserted into the build pipeline went undetected for months. Automated SAST on every build would have flagged the anomalous code patterns introduced by the attacker.
• Capital One (2019): An SSRF vulnerability in a web application firewall configuration allowed access to cloud metadata and 106 million customer records. SAST detects SSRF patterns (CWE-918) as a standard check.
• British Airways (2018): Attackers injected malicious JavaScript into the payment page through a supply chain attack. SAST with dependency analysis would have flagged the compromised third-party script.

Gartner estimates that 70% of application security testing will shift to developers by 2026. SAST is the primary mechanism for that shift because it operates in the developer's existing workflow—code editor, pull request, pre-commit hook—rather than requiring separate security testing environments.

CodeSlick delivers SAST across 5 languages with 294 security checks and three deployment options:

• Free web scanner: Paste or upload code, get results in under 3 seconds. No signup required.
• GitHub App: Install in one click. Runs automatically on every pull request with inline findings and SARIF upload to the GitHub Security Tab.
• CLI: Pre-commit hook integration for local scanning before code leaves the developer's machine.

Every finding includes CWE classification, CVSS 3.1 severity scoring, and AI-powered fix suggestions. Beyond traditional SAST, CodeSlick adds secrets detection (38 patterns), malicious package detection (66 packages), AI code detection (150 signals), and SBOM generation—combining SAST, SCA, and secrets scanning in a single tool.