CWE-154: Improper Neutralization of Variable Name Delimiters

What is Improper Neutralization of Variable Name Delimiters?

• Overview: Improper Neutralization of Variable Name Delimiters (CWE-154) occurs when a software product receives input containing special elements that are not correctly neutralized. These elements can be interpreted as variable name delimiters, potentially altering the intended processing flow.

• Exploitation Methods:

• Attackers can inject special delimiters, such as "$" for environment variables, to manipulate the way data is parsed or processed.
• Common attack patterns include injecting variable delimiters into input fields to change variable references, leading to unauthorized behavior.

• Security Impact:

• Direct consequences of successful exploitation include unauthorized access to sensitive data or the execution of unintended commands.
• Potential cascading effects can involve system instability or data corruption as a result of unexpected variable resolution.
• Business impact may involve data breaches, loss of customer trust, and potential legal repercussions.

• Prevention Guidelines:

• Specific code-level fixes include validating and sanitizing all input to ensure that special elements are neutralized before processing.
• Security best practices involve using input validation libraries and avoiding direct handling of variable names from untrusted sources.
• Recommended tools and frameworks include static analysis tools to detect improper neutralization and utilize secure coding guidelines to prevent such vulnerabilities.

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Technical Details

Likelihood of Exploit: Not specified

Affected Languages: Not Language-Specific

Affected Technologies: Not specified

Vulnerable Code Example

JavaScript Example

// This code is vulnerable to CWE-154: Improper Neutralization of Variable Name Delimiters

function getConfigValue(config, key) {
    // User-controlled input for key should not be directly used
    // as a delimiter in accessing object properties
    return config[key];  // Direct use of user input as key
}

const userInput = process.argv[2];  // Simulating user input
const config = {
    "validKey": "someValue",
    "anotherKey": "anotherValue"
};

console.log(getConfigValue(config, userInput));  // Potential security risk

Explanation of the Vulnerability

In this example, the function getConfigValue uses a user-controlled input key to access properties of an object config. This can lead to security issues such as unauthorized access to object properties or prototype pollution if the input is not properly validated. An attacker might input a key that could access unintended properties or manipulate the object in unexpected ways.

How to fix Improper Neutralization of Variable Name Delimiters?

To mitigate this vulnerability, you can apply the following strategies:

1. Whitelist Valid Keys: Implement a whitelist of allowed keys to restrict access to only known, safe properties.
2. Input Validation: Validate the input to ensure it matches expected patterns and does not include any malicious content.
3. Use of a Safe Map: Instead of using plain objects, use constructs like Map that do not have prototype properties, reducing the risk of prototype pollution.

Fixed Code Example

// Fixed code with comments explaining the security controls implemented

function getConfigValue(config, key) {
    const validKeys = ["validKey", "anotherKey"];  // Define a whitelist of valid keys

    if (validKeys.includes(key)) {  // Check if the provided key is in the whitelist
        return config[key];  // Safe use of user input after validation
    } else {
        throw new Error("Invalid configuration key");  // Handle invalid key scenario
    }
}

const userInput = process.argv[2];  // Simulating user input
const config = {
    "validKey": "someValue",
    "anotherKey": "anotherValue"
};

try {
    console.log(getConfigValue(config, userInput));
} catch (error) {
    console.error(error.message);  // Handle invalid key scenario
}

Explanation of the Fix

In the fixed example, we implement a whitelist of valid keys to ensure that only known and safe properties of the configuration object can be accessed. By checking if the key is included in the validKeys array, we prevent unauthorized access to object properties. This approach helps to mitigate the security risks associated with improper neutralization of variable name delimiters. Additionally, throwing an error for invalid keys provides a clear mechanism to handle unexpected input scenarios.