OWASP Top 10 API Security: Unrestricted Resource Consumption

Share Now
ResilientX Security - OWASP Top 10 API Security: Unrestricted Resource Consumption

Introduction to Unrestricted Resource Consumption

In the digital age, APIs (Application Programming Interfaces) play a crucial role in enabling communication and data exchange between different software systems. However, with the increasing reliance on APIs, it is important to address potential security vulnerabilities that can arise. One such vulnerability is unrestricted resource consumption, which can lead to various negative impacts, including denial of service (DoS) attacks and increased operational costs. In this article, we will explore the threat agents, attack vectors, security weaknesses, and impacts associated with API4:2023 unrestricted resource consumption. We will also provide examples of attack scenarios and discuss preventive measures to mitigate these risks.

Threat Agents and Attack Vectors

Threat Agents

The threat agents for API4:2023 unrestricted resource consumption can vary, but they typically include malicious individuals or automated tools designed to exploit vulnerabilities in APIs. These threat agents can be categorized as:

  1. External attackers: These are individuals or groups who attempt to exploit vulnerabilities in APIs for personal gain or to cause disruption.
  2. Malicious insiders: Insiders with authorized access who misuse their privileges to exploit APIs for malicious purposes.
  3. Automated bots: Programs or scripts that are designed to automatically send a high volume of API requests to exhaust system resources.

Attack Vectors

The attack vectors for API4:2023 unrestricted resource consumption are typically focused on overwhelming the target API with excessive requests or consuming excessive resources. Some common attack vectors include:

  1. High-volume requests: Attackers can send a large number of API requests from a single local computer or by utilizing cloud computing resources. This can quickly overload the target API’s service rate and exhaust its resources.
  2. Parameter manipulation: Attackers can craft API requests with parameters that control the number of resources to be returned. By manipulating these parameters, they can force the API to consume excessive resources.
  3. Response analysis: Attackers can analyze the response status, time, or length of API requests to identify potential weaknesses. By exploiting these weaknesses, they can cause resource exhaustion.
  4. Batched operations: APIs that support batched operations are particularly vulnerable. Attackers can leverage batched operations to execute a large number of resource-intensive tasks within a single API request.

Security Weaknesses

API4:2023 unrestricted resource consumption is rooted in security weaknesses that exist in APIs. These weaknesses include:

  1. Lack of resource limits: Many APIs fail to implement appropriate limits on client interactions or resource consumption. This allows attackers to exploit the API by overwhelming it with excessive requests or consuming excessive resources.
  2. Insufficient input validation: APIs may lack proper validation mechanisms for incoming parameters and payloads. Without proper validation, attackers can manipulate input data to force resource consumption beyond acceptable limits.
  3. Inadequate rate limiting: APIs often lack effective rate limiting mechanisms to control the frequency of client interactions. Without rate limits, attackers can bombard the API with a high volume of requests, leading to resource exhaustion.
  4. Poor query string and request body validation: APIs may not implement thorough validation for query string and request body parameters. Attackers can manipulate these parameters to control the number of records returned in the API response, leading to excessive resource consumption.


API4:2023 unrestricted resource consumption can have severe impacts on both the technical and business aspects of an organization. The impacts include:

  1. Denial of Service (DoS): By overwhelming an API with excessive requests, attackers can cause a DoS condition, rendering the API unavailable to legitimate users and disrupting business operations.
  2. Increased operational costs: Unrestricted resource consumption can result in higher operational costs for the organization. This includes costs related to infrastructure, such as increased CPU demand and cloud storage needs, resulting from the excessive resource consumption.
  3. Service degradation : When an API’s resources are exhausted, the quality of service provided by the API may degrade, leading to slower response times and degraded functionality.
  4. Reputational damage: A successful attack on an API can significantly damage the organization’s reputation, leading to loss of customer trust and potential financial losses.

Example Attack Scenarios

To illustrate the impact of API4:2023 unrestricted resource consumption, let’s examine three attack scenarios.

Scenario #1: SMS Flood Attack

A social network implements a “forgot password” flow that involves sending a one-time token via SMS to reset a user’s password. The flow includes API calls to initiate the password reset and send the SMS using a third-party API.

An attacker writes a script that sends a large number of “forgot password” API calls to the social network’s API. Each API call triggers an SMS request to a third-party API that charges $0.05 per request. By flooding the social network’s API with tens of thousands of requests, the attacker causes the company to lose thousands of dollars in a short period.

Scenario #2: GraphQL Memory Exhaustion

A GraphQL API endpoint allows users to upload profile pictures. The API generates multiple thumbnails based on the uploaded picture, which consumes a significant amount of server memory.

Although the API implements rate limiting and checks for uploaded picture sizes, an attacker bypasses these mechanisms by leveraging the flexibility of GraphQL. The attacker sends a series of API requests to upload pictures, exceeding the server’s memory capacity. This results in a denial of service as the server becomes overwhelmed with memory-intensive operations.

Scenario #3: Uncontrolled File Downloads

A service provider offers an API that allows clients to download large files stored in cloud object storage. The API relies on a cache service to improve service rates and reduce bandwidth consumption. However, the cache service has a maximum file size limit of 15GB.

When a file is updated and its size increases to 18GB, all clients immediately start pulling the new version. Due to the absence of consumption cost alerts or a maximum cost allowance, the service provider incurs a significant increase in monthly bills, from an average of $13 to $8,000.

How to Prevent API4:2023 Unrestricted Resource Consumption

To mitigate the risks associated with API4:2023 unrestricted resource consumption, organizations can implement the following preventive measures:

  1. Use resource limitation solutions: Employ containerization or serverless code frameworks (e.g., Lambdas) that make it easy to limit resources such as memory, CPU, number of restarts, file descriptors, and processes. These solutions provide better control over resource consumption.
  2. Implement input validation: Define and enforce maximum size limits for all incoming parameters and payloads. This includes setting maximum length for strings, the maximum number of elements in arrays, and maximum upload file size. Proper input validation helps prevent resource exhaustion caused by malicious manipulation.
  3. Apply rate limiting: Implement rate limiting mechanisms to control how often clients can interact with the API within a defined timeframe. Fine-tune rate limiting based on business needs, ensuring that different API endpoints have appropriate rate limiting policies.
  4. Limit single operation execution: Restrict the number of times or frequency at which a single API client/user can execute a specific operation. For example, limit the validation of a one-time password or password recovery requests without requiring a visit to a one-time URL.
  5. Perform server-side validation: Implement comprehensive server-side validation for query string and request body parameters. Specifically, validate parameters controlling the number of records to be returned in the API response, preventing excessive resource consumption.
  6. Configure spending limits and alerts: Set spending limits for all service providers/API integrations. If setting spending limits is not possible, configure billing alerts to monitor and control costs associated with resource consumption.

By implementing these preventive measures, organizations can significantly reduce the risk of API4:2023 unrestricted resource consumption and protect their APIs from malicious attacks while ensuring efficient resource allocation and cost management.


API4:2023 unrestricted resource consumption poses a significant security risk to APIs, potentially leading to denial of service attacks and increased operational costs. By understanding the threat agents, attack vectors, security weaknesses, and impacts associated with this vulnerability, organizations can take proactive steps to mitigate these risks. Implementing resource limitations, input validation, rate limiting, and other preventive measures discussed in this article can help safeguard APIs and maintain their integrity, availability, and affordability.

Sign up for ResilientX Security Newsletter