Business Logic Vulnerability – Examples and Attack Prevention

Breaking into an organisation’s IT infra doesn’t always require complex methods. Hackers often exploit normal applications and API functions in unexpected ways to access sensitive data.

For example, the 2019 Venmo breach involved the exploitation of an open API to scrape millions of payment records. A design oversight in the API allowed attackers to exploit its normal functions in an unintended manner—scraping payment records without proper authorization.

This incident highlights a critical business logic flaw that stemmed from a security misconfiguration – a critical API threat ranked #7 on the OWASP API top 10 2023 list.

What is Business Logic Vulnerability?

Business logic vulnerability is a security weakness that arises from flaws in the design and implementation of an application’s business logic.

At its core, business logic defines the rules and processes that drive an application’s behavior in alignment with the organization’s objectives.

The business logic attack exploits these weaknesses, allowing attackers to manipulate the application’s intended functionality.

Such manipulation can lead to unauthorized actions, data breaches, financial losses, and other harmful consequences.

How Do Business Logic Vulnerabilities Arise?

These vulnerabilities often stem from various factors and scenarios:

Misinterpretation of Requirements: One common way is through a misunderstanding or misinterpretation of the business requirements during the development process. Developers may fail to fully grasp the workings of the business processes they are attempting to translate into code, leading to inconsistencies or oversights in the implementation.

Complex Interactions and Edge Cases: Modern applications often involve complex interactions between different components, such as databases, APIs, and external services. A successful business logic attack can happen when developers fail to account for all possible scenarios or edge cases in these interactions.

Unanticipated Usage Scenarios: Sometimes, business logic vulnerabilities arise from scenarios that were not considered during the design and development phases. These scenarios may involve unexpected combinations of inputs or actions that result in unintended behavior or security vulnerabilities.

Examples of Business Logic Vulnerabilities

1. Unlimited Discounts: Vulnerable Coupon Code

An e-commerce platform offers users a one-time-use coupon code for discounts at checkout, which is common and effective for boosting sales and customer satisfaction.

However, the application was designed with a flaw: it didn’t validate the number of times a coupon code could be used by a single user. As a result, an attacker discovered that the same coupon code could be reused indefinitely.

Use case:

• An attacker makes a legitimate purchase using the coupon code & gets a discount.
• Then he realizes that the application does not cancel the coupon code after use.
• He repeatedly uses the same coupon code to make multiple purchases at a discounted rate, leading to potential financial damage to the business.

2. The Faulty Wallet Vulnerability

This business logic vulnerability occurs when a wallet always throws an exception when receiving funds, causing the entire transaction to fail. Despite the transaction failing, the wallet incorrectly shows the funds as credited, while the bank’s balance remains unchanged.

This mismatch between the wallet’s displayed balance and the actual transaction status can lead to confusion and reconciliation issues.

For example:

1. The attacker first creates a wallet.
2. The attacker transfers an appropriate amount to the wallet.
3. During the transaction, an exception is thrown, causing the entire transaction to revert.
4. Due to a logical flaw, the amount intended for the wallet appears to be credited, even though the transaction is reverted, and the bank balance is not reduced.
5. The attacker repeats the transaction process multiple times.
6. Once a substantial amount of funds has accumulated in the wallet, the attacker transfers the funds and cashes out, stealing them without debiting the bank’s balance.

How To Detect Business Logic Vulnerabilities?

Business logic vulnerabilities are often overlooked by many companies. Most companies only become aware of these flaws when monetary losses occur.

While automated vulnerability scanners are effective at finding technical flaws like SQLi and XSS, they struggle to grasp complex situations or bypass controls.

Since automation cannot fully address business logic abuse cases, these vulnerabilities require manual penetration testing.

Effective detection of business logic vulnerabilities relies on the tester’s expertise and comprehensive understanding of the business process and its rules. Testers must think unconventionally, simulate diverse misuse scenarios, and use techniques akin to those employed by functional testers.

A key best practice is to test for unusual use cases in your application. For example, in a web application with a multi-step checkout process, what happens if a user skips the payment step and tries to access the order confirmation page directly? Does the application grant access, deny it, or show an error message?

Testing these scenarios helps identify how the application handles unexpected behaviors and potential vulnerabilities. Here are the key areas to focus on during testing:

• Money-Related Application Logics: These govern online monetary transactions, deals, discounts, refunds, shipping fees, etc.
• Time-Related Application Logics: These determine how web applications manage user sessions and timeouts.
• Process-Related Application Logics: Internal-facing applications, like those for human resources management, procurement, and warehousing, can also be exploited.

Best Practices to Prevent Business Logic Attacks

Preventing the exploitation of business logic flaws requires a comprehensive approach. Here are some best practices:

Threat Modeling: Conduct threat modeling exercises to identify potential attack vectors and prioritize security controls accordingly. This involves analyzing the application’s architecture, data flows, and trust boundaries to anticipate potential threats.

Implementing Proper Authentication: Utilize strong authentication mechanisms, such as multi-factor authentication (MFA), to add a robust security layer by requiring multiple verification factors, making it significantly harder for attackers to exploit weaknesses, even if they gain access to user credentials.

Transaction Integrity: Implement mechanisms to ensure the integrity of transactions, such as using cryptographic techniques to sign and verify sensitive data and transactions.

Immutable Audit Trails: Maintain immutable audit trails to track and monitor user actions and detect any unauthorized or anomalous behavior.

Business Logic Layer: Segregate the business logic layer from presentation and data layers to prevent users’ or attackers’ direct manipulation of business logic.

Defensive Programming: Adhere to defensive programming practices, such as input validation, error handling, and secure coding standards, to mitigate common vulnerabilities like injection attacks and improper error handling.

Secure Configuration Management: Ensure that application configurations are securely managed and do not expose sensitive information or weaken security controls.

Secure API Design: If the application exposes APIs, design them with security in mind, including proper authentication, authorization, input validation, and rate limiting to prevent business logic attacks.

Secure Data Handling: Implement proper data handling practices, including encryption, data masking, and access controls, to protect sensitive information from unauthorized access or disclosure.

Regular Security Reviews: Conduct regular security reviews and threat assessments to identify emerging threats and vulnerabilities and update security controls accordingly.

Tackling Business Logical Vulnerability with AppTrana WAAP

Addressing business logic vulnerabilities effectively requires more than just automated tools. AppTrana’s WAAP combines an integrated DAST scanner with expert penetration testing to uncover these complex issues.

The DAST scanner automatically detects security issues like SQL injections and Cross-site Scripting (XSS) and assesses their severity to help prioritize fixes.

Alongside automated scanning, AppTrana also includes a pentesting add-on where expert penetration testers analyze the expected and unexpected behaviors of your website or application, to identify business logic vulnerabilities.

Thereby they create and test various attack scenarios, helping to uncover vulnerabilities that automated tools might miss.

Identifying logic vulnerabilities is meaningless unless you fix them. Autonomously patch the identified vulnerabilities with SwyftComply on AppTrana WAAP.

Indusface’s managed service team collaborates with your team to understand your applications and their intended functionality. After careful analysis, they help create and implement custom policies to ensure your application operates as intended.

Furthermore, AppTrana provides visibility into attempted attacks and insights about attackers. This information helps take proactive measures to detect and block business logic attacks, enhancing your application’s security posture.

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