Static Application Security Testing (SAST): What You Need to Know

By Jit

Published January 24, 2025.

a screenshot of a web page with the text core concepts of static application security

Modern software applications operate within increasingly complex ecosystems, spanning multiple layers of the stack—from the user interface and application logic to APIs, databases, and third-party dependencies. Each layer introduces unique vulnerabilities, often requiring specialized domain expertise to identify and mitigate.

Static Application Security Testing (SAST) offers a proactive solution, enabling teams to identify and resolve security issues at the very early stages of the development cycle, before they escalate into critical problems. This is also what is more commonly referred to as “shift-left”, meaning shifting security as far left as possible in the software development lifecycle (SDLC).

What is Static Application Security Testing (SAST)?

SAST, is a security technique designed to analyze an application’s source code, bytecode, or binaries for vulnerabilities without requiring the program to execute. Unlike dynamic testing methods that interact with running applications, SAST focuses solely on the static elements of the codebase. By operating in a pre-runtime context, SAST tools can identify issues such as insecure API calls, hardcoded secrets, or unsafe data handling patterns before they become active threats.

What’s the Purpose of SAST?

The primary goal of SAST is to empower development teams to address vulnerabilities at their inception. By identifying issues early in the SDLC, SAST minimizes the cost and complexity of remediation. This proactive approach helps prevent security flaws from propagating through subsequent stages, reducing the risk of exploitation in production environments. Furthermore, integrating SAST into CI/CD pipelines ensures continuous feedback for developers, fostering a culture of secure coding and enabling teams to maintain high security standards as their applications evolve.

How SAST Works

SAST tools function by parsing the codebase and constructing an abstract syntax tree (AST) or control flow graph (CFG) to model the structure and behavior of the application. These representations allow the tool to do the following:

Lexical Analysis: Analyze the source code line by line, identifying syntactic patterns that match predefined security rules. For example, it can flag unsafe uses of functions like eval() or detect hard coded credentials.
Semantic Analysis: Understand the relationships and data flows within the code. This step helps identify vulnerabilities such as SQL injection, where unsanitized user input traverses into a database query without proper validation.
Data Flow Analysis: Track how data moves through the application, focusing on sources (e.g., user input), sinks (e.g., database queries or system calls), and transformations (e.g., sanitization functions). For instance, the tool can detect if user input flows into a SQL query without being sanitized.
Taint Analysis: Mark untrusted inputs as "tainted" and follow their propagation through the code. This method detects cases where untrusted data influences sensitive operations, such as file system access or command execution.
Pattern Matching and Rule Application: Apply a library of security rules to identify code segments that violate best practices. These rules can range from generic (e.g., detecting hardcoded passwords) to language-specific (e.g., improper use of Go’s os/exec package).
Control Flow and Dependency Analysis: Examine the execution paths and external dependencies of the application. This can reveal vulnerabilities caused by insecure third-party libraries or unguarded conditional branches.

By integrating these techniques, SAST tools provide a detailed map of potential vulnerabilities, highlighting both the root causes and their broader implications in the application’s logic.

Examples of vulnerabilities detected by Static Application Security testing (SAST)

SAST tools rely on predefined rules to detect common and emerging security vulnerabilities by scanning codebases for unsafe patterns, insecure function calls, and improper data handling practices, as noted above. These rules are continuously updated to reflect the latest security research, ensuring ongoing protection against evolving threats. By applying both generic and language-specific rules, SAST tools provide broad and deep coverage of potential vulnerabilities, enabling development teams to stay ahead of attackers.

Below we’re going to dive into a few examples using rules from Semgrep, a best of breed open source SAST tool with wide programming language coverage.

SAST Detection Example: SQL Injection Vulnerability

This example will demonstrate a rule that detects unsafe query constructions where user input is directly concatenated into SQL queries:

conn.execute("SELECT * FROM users WHERE name = " + user_input)

This rule identifies code segments where user input is not sanitized, leaving applications vulnerable to SQL injection attacks.

Suggested Remediation: Always use parameterized queries or prepared statements. These techniques separate SQL logic from data, ensuring that user input is treated as data rather than executable code.

Insecure Function Usage

This will flag the use of functions known for their security risks, such as eval:

eval($X)

This pattern alerts developers to replace insecure functions with safer alternatives.

Suggested Remediation: Replace eval() with safer alternatives, such as JSON.parse() for JSON data or direct function calls for predefined operations. Avoid executing dynamic code unless absolutely necessary.

Improper Input Validation

This example highlights areas where user input is processed without adequate validation:

input = get_user_input()

This rule enforces the need for input sanitization and validation to prevent injection attacks and other exploits.

Suggested Remediation: Implement strict input validation rules. Use libraries or frameworks like Django Validators, Joi (for JavaScript), or OWASP’s ESAPI to define strict constraints for input length, format, and allowed characters. Implement validation at the API layer and ensure rules are consistently applied across all user inputs, rejecting anything that falls outside the defined constraints.

Additionally, sanitize inputs before using them in sensitive operations. Sanitizing input neutralizes harmful characters, preventing exploits like SQL injection or XSS. It complements validation by ensuring data passed to sensitive operations is safe, even if validation is bypassed.

Benefits of Static Application Security Testing

Early Detection of Vulnerabilities: SAST identifies vulnerabilities during the coding phase, enabling developers to resolve issues before they impact downstream processes. This early intervention minimizes the risk of releasing flawed software into production.
Cost Efficiency: Studies show that addressing vulnerabilities in the early development stages is significantly more cost-effective than resolving them after deployment. SAST provides a cost-efficient mechanism to bolster security without inflating budgets.
Improved Code Quality: Beyond security, SAST encourages developers to adhere to best coding practices, as many SAST tools include code quality checks that enforce best practices, such as avoiding overly complex functions, ensuring proper naming conventions, and maintaining code readability. This emphasis on secure coding results in more maintainable and robust codebases.
Regulatory Compliance: For organizations bound by regulatory frameworks like PCI DSS or GDPR, SAST tools offer a systematic way to meet security requirements. These tools generate audit-ready reports that demonstrate adherence to industry standards.
Integration with IDEs and CI/CD Pipelines: Modern SAST solutions integrate seamlessly with integrated development environments (IDEs) and CI/CD pipelines. This integration ensures that security becomes an intrinsic part of the development workflow, reducing friction for developers and enhancing overall productivity.

To derive these benefits there are some key features you should prioritize when selecting the right SAST tool for your stack.

Key Features to Look for in Static Application Security Testing

A well-chosen tool can seamlessly integrate into your workflows, enhance productivity, and ensure comprehensive security coverage, while providing the benefits above.

Consider the Developer Experience (DX): The success of any SAST tool hinges on its usability––and developers will be the primary consumers of the SAST tooling you select. Tools must offer an intuitive interface and seamless workflows to ensure developers adopt them willingly. Poor DX can render even the most powerful tools ineffective.
Reduce Cognitive Load by Automating Triage: Which brings us to the next critical features. A critical piece in DX and adoptability is your SAST solution’s ability to automate the triage of vulnerabilities––and do so well. It should be able to categorize them based on predefined criteria such as exploitability and impact, not just an arbitrary CVE scale. Automation minimizes manual effort and ensures that critical issues receive timely attention.
Contextual Prioritization is Key: The automated triage is a product of modern SAST tools’ ability to prioritize vulnerabilities by considering their runtime context. For instance, vulnerabilities in production-facing code or externally accessible systems should take precedence over those in less critical areas.
Unified with Other AppSec Tools: Just like other engineering domains, AppSec can no longer be siloed to understand the entire application logic and context required to properly prioritize and triage vulnerabilities. Avoid tool sprawl by choosing a platform that unifies SAST with other application security tools. A unified approach streamlines workflows, reduces complexity, and enhances overall efficiency.
In a Polyglot Multiverse: Opt for Comprehensive Language Support Just like most engineering organizations are running on multiple clouds, and leveraging a diversity of tools per team and stack––the same goes for programming languages. A comprehensive SAST solution should support a wide range of programming languages, ensuring coverage across diverse codebases. This will also future proof your decision, in the event that you need to integrate a new language for specific engineering considerations. The wider the coverage, the greater confidence you will have that it will stick with your team in the long-term.
Accuracy: False positives and negatives can erode trust in SAST tools, likewise inability to properly triage or contextualize prioritization of threats. When our tooling gets this wrong, and is unable to properly flag the most critical issues we should be working on immediately, then developers abandon these tools, and security is compromised. High accuracy is essential for actionable insights that developers can rely on.
Reporting Capabilities: For Transparency and Levelling Up Effective reporting allows organizations to identify security gaps, mitigate them, and measure progress over time. It enables greater transparency around AppSec, which always seems to be perceived as a black box, and to continuously level up security hygiene and practices. Look for tools that provide customizable, audit-friendly reports for internal and external stakeholders.

Common Static Application Security Testing Tools

Selecting the right SAST tool for your needs involves balancing customization, integration, and developer-friendly features. This is because not all SAST tools provide the same depth or breadth of analysis across the techniques mentioned, such as lexical analysis, semantic analysis, data flow tracking, and taint analysis. Some tools may focus on basic pattern matching or rule-based detection, while others incorporate advanced techniques like dependency analysis or contextual prioritization.

Among the most popular options:

Opengrep focuses on rule-based pattern matching and provides great flexibility for lightweight and customizable analysis, but it may lack more advanced capabilities like deep taint analysis or comprehensive dependency mapping.
Veracode and Coverity typically include robust semantic and data flow analysis, making them more suitable for complex applications or enterprise use cases where a detailed understanding of application logic is essential.
Jit differentiates itself by adding a contextual prioritization layer that leverages runtime information to focus on vulnerabilities that pose the most immediate risk.

The convergence of the many layers of product code, APIs and data, and the third-party libraries they employ, creates an intricate web of interdependencies, where a single flaw can cascade into significant security risks. For instance, front-end vulnerabilities might involve cross-site scripting (XSS), while back-end systems contend with issues like insecure deserialization or SQL injection.

Open source third-party dependencies and libraries that have become increasingly ubiquitous in modern stacks, add another layer of risk through potential supply chain attacks. This multifaceted environment makes it essential to adopt comprehensive and proactive security practices capable of tackling vulnerabilities across all layers of the application stack.

Static Application Security Testing (SAST) is the backbone of building secure, reliable software, and adopting a developer-friendly approach that is key to the success of your AppSec programs. There are many excellent open source tools that you can explore, alongside Jit which offers a proactive, unified solution that integrates seamlessly into your workflows, ensuring you can identify and remediate vulnerabilities without disrupting your development process.

Ready to streamline your security management? Try Jit today and experience how developer-focused SAST can transform the way you build secure applications.