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Top API Vulnerabilities and 6 Ways to Mitigate Them

October 4, 2023
Nedim Maric

What Are API Vulnerabilities? 

API vulnerabilities refer to the potential weaknesses or gaps in an API’s security that could be exploited by a malicious actor. These vulnerabilities can be present in any part of the API, from the design phase to the deployment stage. They can result in severe consequences, such as data breaches, unauthorized access, and even system crashes.

Despite the significant role that APIs play in software applications, they are often left unprotected due to misconfigurations, lack of security measures, or simply unawareness of the potential risks. This lack of protection can provide an open door for hackers to exploit these vulnerabilities and gain unauthorized access to sensitive data or systems.

Understanding these API vulnerabilities is the first step to mitigating the risks they pose. By comprehending the potential threats and implementing the appropriate security measures, developers can ensure the safety and integrity of their APIs.

In this article:

What Is the OWASP API Security Top 10?

OWASP, or the Open Web Application Security Project, is an international non-profit organization dedicated to improving software security. The OWASP API Security Top 10 is a list of the most critical API security risks, compiled by security experts from around the world. It was last updated in 2023.

The OWASP Top 10 serves as a standard guideline for businesses and developers to understand and mitigate the risks associated with API security. This list is updated regularly to reflect the evolving threat landscape. The 2023 list includes, in order of severity: Object Level Authorization, Broken Authentication, Broken Object Property Level Authorization, Unrestricted Resource Consumption, Broken Function Level Authorization, Unrestricted Access to Sensitive Business Flows, Server Side Request Forgery, Security Misconfiguration, Improper Inventory Management, and Unsafe Consumption of APIs.

Each of these risks represents a potential vulnerability in your API security architecture. By understanding these risks, you can take proactive steps to ensure that your APIs are as secure as possible.

Common API Security Vulnerabilities

Broken Object-Level Authorization

Broken Object-Level Authorization is one of the most common API vulnerabilities. It occurs when an API fails to validate a user’s authorization to access certain data objects. This vulnerability could allow an unauthorized user to access, manipulate, or delete data that they should not have access to.

To mitigate this risk, developers should implement proper object-level authorization checks for each API endpoint. This involves validating the user’s rights and permissions for each request they make, ensuring that they are only able to access the data they are authorized to.

Broken User Authentication

Broken User Authentication occurs when an API does not correctly authenticate a user’s identity before granting them access. This can lead to unauthorized users gaining access to sensitive data or systems.

To protect against this vulnerability, developers should implement strong user authentication mechanisms, such as two-factor authentication or biometric authentication. Additionally, they should also ensure that session management is securely handled, preventing unauthorized users from hijacking user sessions.

Injection Attacks

Injection attacks are among the most notorious API vulnerabilities. They occur when an attacker injects malicious code into an API request, tricking the API into executing unintended commands. This can result in data breaches, data corruption, or even full-scale system takeovers.

Developers can mitigate this risk by employing robust input validation measures. By validating and sanitizing all data entering the API, developers can prevent harmful code from ever reaching the API.

Excessive Data Exposure

Excessive Data Exposure is a vulnerability where an API unintentionally exposes more data than necessary in its responses. This can provide attackers with invaluable information, aiding them in future attacks.

To mitigate this vulnerability, developers should adopt a policy of providing the least amount of data necessary in their API responses. This can be achieved through proper data filtering and limiting the amount of data returned in each API response.

Lack of Rate Limiting

Lack of Rate Limiting is when an API does not limit the number of requests a user or system can make over a given timeframe. This can lead to potential Denial-of-Service (DoS) attacks, where an attacker floods the API with requests, causing it to become unresponsive.

Developers can protect against this vulnerability by implementing rate limiting on their APIs. This involves setting a limit to the number of requests a user or system can make within a certain timeframe, preventing potential DoS attacks.

Insecure Direct Object Reference (IDOR)

Insecure Direct Object Reference (IDOR) is a vulnerability where an API exposes direct references to internal implementation objects. This can allow an attacker to manipulate these references and gain unauthorized access to data.

To prevent this vulnerability, developers should avoid exposing direct references to internal objects in their APIs. Instead, they should use indirect references, making it more difficult for an attacker to manipulate the references and gain unauthorized access.

6 Ways to Mitigate API Security Vulnerabilities 

Here are the basic ways you can prevent attackers from exploiting common API security vulnerabilities.

1. Input Validation and Sanitization

Input validation and sanitization is the first line of defense against API vulnerabilities. This process involves verifying the integrity and legitimacy of data before it is processed by the API. This can prevent a wide range of attacks, including SQL injection, cross-site scripting (XSS), and remote code execution.

To implement input validation, you should start by defining a strict schema for each API endpoint. This schema should specify the type, format, and range of acceptable values for each input. It should also reject any input that does not conform to this schema.

After validating the input, you should sanitize it by removing any potentially harmful content. This can include special characters, HTML tags, and scripts. This process can prevent injection attacks, where an attacker tries to insert malicious code into your application through the API.

2. Strong Authentication and Authorization

Strong authentication and authorization are crucial to ensuring that only authorized users can access your API. This can prevent unauthorized access and data breaches, which are among the most common types of API vulnerabilities.

Authentication refers to the process of verifying the identity of a user or a system. This can be achieved through various methods, such as passwords, tokens, or biometric data. To strengthen your authentication process, you should consider implementing multi-factor authentication, which requires users to provide two or more pieces of evidence to verify their identity.

Authorization, on the other hand, refers to the process of determining what actions a user or a system is allowed to perform. This can be based on roles, permissions, or access control lists. To strengthen your authorization process, you should implement the principle of least privilege, which means giving each user or system the minimum permissions they need to perform their tasks.

3. Rate Limiting and Throttling

Rate limiting and throttling are effective measures to protect your API from denial-of-service (DoS) attacks, brute force attacks, and other forms of abuse. These techniques limit the number of requests that a user or a system can make to your API within a certain period.

Rate limiting sets a cap on the number of requests, while throttling slows down the processing of requests once the limit is reached. These measures can be implemented on a per-user basis, a per-IP basis, or a per-endpoint basis.

However, it’s important to strike a balance between security and usability when implementing rate limiting and throttling. Setting the limits too low can hinder the functionality of your application and irritate your users. On the other hand, setting the limits too high can leave your API vulnerable to attacks.

4. Implement an API Gateway

An API gateway serves as a single entry point for all API traffic, providing a layer of abstraction between your application and the underlying services. This can simplify the management of your API, improve its performance, and enhance its security.

The API gateway can enforce security policies, perform input validation and sanitization, implement rate limiting and throttling, and provide other security features. It can also monitor API traffic, detect unusual patterns, and respond to potential threats.

Learn more in our detailed guide to api security best practices.

5. Using API Vulnerability Scanning Tools

API vulnerability scanning tools are software tools designed to automatically detect security vulnerabilities in your API. They can scan your API for common vulnerabilities, such as SQL injection, cross-site scripting, weak authentication, and insecure data transmission.

These tools can provide a detailed report of the vulnerabilities they find, along with recommendations for remediation. This can save you a lot of time and effort in identifying and fixing vulnerabilities, especially in large and complex APIs.

Learn more in our detailed guide to API security testing tools 

6. Test Your APIs with Dynamic Application Security Testing (DAST)

Bright Security is a DAST tool built from the ground up to test APIs and web applications. With support for a wide range of API architectures, test your legacy and modern applications, including REST API, SOAP and GraphQL.

To compliment DevOps and CI/CD, Bright empowers developers to detect and fix vulnerabilities on every build, reducing the reliance on manual testing by leveraging multiple discovery methods:

  • HAR files
  • OpenAPI (Swagger) files 
  • Postman Collections

Start detecting the technical OWASP API Top 10 and more, seamlessly integrated across your pipelines via:

  • Bright REST API
  • Convenient CLI for developers
  • Common DevOps tools like CircleCI, Jenkins, JIRA, GitHub, Azure DevOps, and more

Learn more about Bright Security for APIs

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