CWE-799: Improper Control of Interaction Frequency

What is Improper Control of Interaction Frequency?

• Overview: Improper Control of Interaction Frequency occurs when a system fails to appropriately limit the number or frequency of interactions with an actor, leading to potential abuse such as spamming requests or executing actions more frequently than intended.

• Exploitation Methods:

• Attackers can exploit this vulnerability by sending a high volume of requests in a short period, overwhelming the system.
• Common attack patterns include brute force attacks, where repeated login attempts are made, and vote stuffing in online polls.

• Security Impact:

• Direct consequences include denial of service, where legitimate users cannot access the service.
• Potential cascading effects include data corruption or logic compromise, such as multiple unauthorized votes.
• Business impact could involve loss of trust, financial loss due to downtime, and increased operational costs.

• Prevention Guidelines:

• Implement rate limiting to control the number of requests from a single user or IP address.
• Employ CAPTCHA or other human verification mechanisms to differentiate between humans and bots.
• Use monitoring and alerting tools to detect unusual interaction patterns and respond in real-time.
• Utilize frameworks with built-in security features to manage request handling and authentication processes.

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Technical Details

Likelihood of Exploit: Not specified

Affected Languages: Not Language-Specific

Affected Technologies: Not specified

Vulnerable Code Example

from flask import Flask, request

app = Flask(__name__)

@app.route('/login', methods=['POST'])
def login():
    # Vulnerable: No rate limiting on login attempts
    username = request.form.get('username')
    password = request.form.get('password')
    if authenticate(username, password):
        return "Login successful"
    else:
        return "Login failed", 401

def authenticate(username, password):
    # Placeholder for actual authentication logic
    return username == "admin" and password == "password"

if __name__ == '__main__':
    app.run()

Explanation

In this vulnerable code example, the /login endpoint does not have any rate limiting. This means an attacker can automate login attempts and perform a brute-force attack by trying numerous password combinations in a short period. This lack of control over interaction frequency can lead to unauthorized access if an attacker guesses the correct password.

How to fix Improper Control of Interaction Frequency?

To mitigate this vulnerability, we should implement rate limiting on the /login endpoint. This can be done by restricting the number of login attempts from a single IP address or user within a specified time frame. We can use libraries like Flask-Limiter to easily integrate rate limits into our Flask application.

Fixed Code Example

from flask import Flask, request
from flask_limiter import Limiter
from flask_limiter.util import get_remote_address

app = Flask(__name__)
limiter = Limiter(app, key_func=get_remote_address)

@app.route('/login', methods=['POST'])
@limiter.limit("5 per minute")
def login():
    # Fixed: Implemented rate limiting to prevent brute-force attacks
    username = request.form.get('username')
    password = request.form.get('password')
    if authenticate(username, password):
        return "Login successful"
    else:
        return "Login failed", 401

def authenticate(username, password):
    # Placeholder for actual authentication logic
    return username == "admin" and password == "password"

if __name__ == '__main__':
    app.run()

Explanation

In the fixed code example, we use the Flask-Limiter library to apply a rate limit to the /login endpoint. The @limiter.limit("5 per minute") decorator ensures that a client can only attempt to log in five times per minute from the same IP address. This rate limiting significantly reduces the risk of successful brute-force attacks by controlling the frequency of login attempts, thereby enhancing the security of the application.