CWE-450: Multiple Interpretations of UI Input

What is Multiple Interpretations of UI Input?

• Overview: This vulnerability occurs when a user interface processes input in multiple ways but fails to alert the user when it defaults to a less secure interpretation, potentially leading to unintended actions or security exposures.

• Exploitation Methods:

• Attackers can exploit this by crafting input that is interpreted in an insecure manner, bypassing security controls.
• Common attack patterns include input that triggers different behavior based on context, such as special characters or ambiguous formats.

• Security Impact:

• Direct consequences include unauthorized actions or data exposure due to the system acting on incorrect or malicious input.
• Potential cascading effects include privilege escalation or further exploitation if the system's state is altered unexpectedly.
• Business impact may involve data breaches, loss of customer trust, or non-compliance penalties.

• Prevention Guidelines:

• Specific code-level fixes involve validating and sanitizing input consistently, ensuring that only secure interpretations are allowed.
• Security best practices include implementing clear user prompts for ambiguous input and logging all input interpretation decisions.
• Recommended tools and frameworks involve using libraries that enforce strict input validation and adopting secure coding standards.

Corgea can automatically detect and fix Multiple Interpretations of UI Input in your codebase. [Try Corgea free today](https://corgea.app).

Technical Details

Likelihood of Exploit: Not specified

Affected Languages: Not Language-Specific

Affected Technologies: Not specified

Vulnerable Code Example

// Function to handle user input for a simple command interpreter
function handleUserInput(input) {
    // Vulnerable: Broad normalization can lead to unintended command execution
    let command = input.trim().toLowerCase();
    // Execute command based on input
    if (command === 'delete') {
        console.log('Executing delete command...');
        // Code to delete content goes here
    } else {
        console.log('Unknown command');
    }
}

// Example of problematic input
handleUserInput(' DELETE ');

In this vulnerable code example, the handleUserInput function uses trim() and toLowerCase() to normalize user input. This can lead to security issues as it allows variations of the input, such as ' DELETE ', to be interpreted as valid commands. This could result in unintended execution of sensitive operations without clear user intent.

How to fix Multiple Interpretations of UI Input?

To fix this vulnerability, we must ensure that user input is explicitly validated against known and secure patterns. Instead of automatically normalizing input, the system should ask for confirmation if there is any ambiguity or deviation from expected formats. This can be achieved by:

1. Prompting for Confirmation: If the input is sensitive, ask the user for confirmation before executing the command.
2. Explicit Matching: Avoid using broad normalization techniques like trim() and toLowerCase() without validation.
3. Pattern Matching: Use specific patterns or regular expressions to validate input strictly.
4. User Feedback: Provide feedback to the user to clarify input expectations.

Fixed Code Example

// Function to handle user input with explicit validation and confirmation
function handleUserInput(input) {
    // Explicitly match input using regular expressions
    const deleteCommandRegex = /^delete\$/i;
    
    // If the input matches the 'delete' command exactly
    if (deleteCommandRegex.test(input.trim())) {
        // Prompt user for confirmation before executing sensitive command
        const confirmation = confirm('Are you sure you want to execute the delete command?');
        if (confirmation) {
            console.log('Executing delete command...');
            // Code to delete content goes here
        }
    } else {
        console.log('Unknown command');
    }
}

// Example usage with confirmation
handleUserInput(' DELETE ');

In the fixed code, we use a regular expression to strictly match the input against the 'delete' command while allowing for case insensitivity. By using input.trim() within the test() method, we ensure that only exact matches are considered. Additionally, we prompt the user for confirmation before executing any sensitive operations, ensuring the user is aware of their actions and reducing the risk of unintended command execution due to multiple interpretations of input.