CWE-440: Expected Behavior Violation

What is Expected Behavior Violation?

• Overview: This vulnerability occurs when a feature, API, or function does not perform according to its specification, leading to unexpected behavior that can be exploited by attackers.

• Exploitation Methods:

• Attackers can exploit this vulnerability by identifying discrepancies between actual and documented behavior to bypass security controls.
• Common attack patterns include manipulating inputs to achieve unintended outputs or leveraging the unexpected behavior to gain unauthorized access or escalate privileges.

• Security Impact:

• Direct consequences of successful exploitation can include unauthorized access to sensitive data, execution of unauthorized actions, or system instability.
• Potential cascading effects may involve further exploitation of other connected systems or services due to trust relationships.
• Business impact can be significant, leading to data breaches, loss of customer trust, and regulatory non-compliance.

• Prevention Guidelines:

• Specific code-level fixes include rigorous input validation, thorough testing of all feature specifications, and ensuring outputs align with expected behavior.
• Security best practices involve maintaining up-to-date documentation, ensuring consistency between code and documentation, and conducting regular security audits.
• Recommended tools and frameworks include using automated testing tools, static code analysis tools, and adopting frameworks that support contract-based programming.

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Technical Details

Likelihood of Exploit: Not specified

Affected Languages: Not Language-Specific

Affected Technologies: ICS/OT

Vulnerable Code Example

JavaScript Example

// A simple API endpoint that returns user profile data based on the user ID
function getUserProfile(userId) {
    // The function assumes that the userId is always valid and that the database query will always succeed
    const userProfile = database.query(`SELECT * FROM users WHERE id = \${userId}`);
    return userProfile;
}

Explanation:

In this vulnerable code example, the function getUserProfile expects that the userId passed is always valid and that the database query will succeed without any error handling. This violates expected behavior by not handling possible exceptions or invalid input, which can lead to security issues such as SQL injection or application crashes. The use of string interpolation for the SQL query makes it susceptible to SQL injection attacks if userId is not properly validated.

How to fix Expected Behavior Violation?

To fix the expected behavior violation, we should:

1. Validate Input: Ensure that the userId is a valid and expected value before using it in a query.
2. Use Parameterized Queries: Protect against SQL injection by using parameterized queries instead of string interpolation.
3. Error Handling: Implement proper error handling to manage unexpected database errors gracefully.
4. Logging: Log any errors or exceptions for monitoring and debugging purposes.

Fixed Code Example

// A secure version of the API endpoint that handles user input validation and database errors
function getUserProfile(userId) {
    // Validate the userId to ensure it is a positive integer
    if (!Number.isInteger(userId) || userId <= 0) {
        throw new Error("Invalid user ID");
    }

    try {
        // Use parameterized query to prevent SQL injection
        const userProfile = database.query("SELECT * FROM users WHERE id = ?", [userId]);
        return userProfile;
    } catch (error) {
        // Log the error and throw a customized error message
        console.error("Database query failed:", error);
        throw new Error("Could not retrieve user profile. Please try again later.");
    }
}

Explanation:

In the fixed code example, we introduce input validation to ensure the userId is a valid positive integer. We use parameterized queries to prevent SQL injection, and we add a try-catch block to handle potential database errors gracefully. By logging the errors, we improve monitoring and make debugging easier, while throwing user-friendly error messages. These changes ensure the function behaves as expected under various conditions, enhancing the security and reliability of the application.