CWE-475: Undefined Behavior for Input to API

What is Undefined Behavior for Input to API?

• Overview: Undefined Behavior for Input to API occurs when a function's behavior is not explicitly defined unless a specific control parameter is set, leading to unpredictable and potentially harmful outcomes.

• Exploitation Methods:

• Attackers can exploit this vulnerability by providing unexpected or malicious input that causes the function to behave unpredictably.
• Common attack patterns include manipulating input parameters to bypass security checks or trigger unintended behavior in the application.

• Security Impact:

• Direct consequences of successful exploitation include application crashes, data corruption, or unauthorized access.
• Potential cascading effects include system instability and vulnerabilities in other parts of the application.
• Business impact can involve data breaches, loss of customer trust, and legal repercussions.

• Prevention Guidelines:

• Specific code-level fixes involve validating all input parameters and ensuring that control parameters are always set to expected values.
• Security best practices include thorough API documentation and implementing input validation and error handling.
• Recommended tools and frameworks include static analysis tools to detect undefined behavior and secure coding frameworks that enforce input validation.

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Technical Details

Likelihood of Exploit: Not specified

Affected Languages: Not Language-Specific

Affected Technologies: Not specified

Vulnerable Code Example

function processRequest(requestType, data) {
    // Vulnerability: Undefined behavior when requestType is not "GET" or "POST"
    if (requestType === "GET") {
        return handleGet(data);
    } else if (requestType === "POST") {
        return handlePost(data);
    }
    // No handling for other values of requestType, leading to undefined behavior
    // This could result in the function returning undefined, causing unexpected behavior in the application
}

How to fix Undefined Behavior for Input to API?

To fix this issue in JavaScript, implement input validation to ensure that all possible request types are handled. A default case should be added to handle any unexpected inputs, which can log an error or throw an exception, ensuring that the program does not continue in an undefined state.

Fixed Code Example

function processRequest(requestType, data) {
    if (requestType === "GET") {
        return handleGet(data);
    } else if (requestType === "POST") {
        return handlePost(data);
    } else {
        // Handle undefined behavior by throwing an error
        // This ensures that the function has a defined outcome for all inputs
        throw new Error(`Unsupported request type: \${requestType}`);
    }
}

In both examples, the fix involves validating the input and handling unexpected values gracefully. This approach ensures the code remains robust and secure against undefined behavior due to unexpected input values. By clearly defining behavior for all possible inputs, the code avoids potential errors and security issues that could arise from unhandled cases.