What is Improper Restriction of Excessive (CWE-307)?

TL;DR: Improper Restriction of Excessive Authentication Attempts (CWE-307) allows attackers to perform brute force attacks by repeatedly attempting logins. Fix this by implementing rate limiting and account lockout measures.

What is Improper Restriction of Excessive Authentication Attempts?

Improper Restriction of Excessive Authentication Attempts (CWE-307) is a type of vulnerability that occurs when an application does not implement sufficient measures to prevent multiple failed authentication attempts within a short time frame. As defined by the MITRE Corporation under CWE-307, and classified by the OWASP Foundation under A07:2025 - Authentication Failures…

Quick Summary

Improper Restriction of Excessive Authentication Attempts is a critical vulnerability that allows attackers to perform brute force attacks on user accounts. This can lead to unauthorized access and compromise sensitive data. Jump to: What is Improper Restriction of Excessive Authentication Attempts? · Overview · How It Works · Business Impact · Attack Scenario · Detection · Fix · Framework-Specific Fixes · Ask AI · Best Practices · FAQ · Vulnerabilities Related

Jump to: Quick Summary · Improper Restriction of Excessive Authentication Attempts Overview · How Improper Restriction of Excessive Authentication Attempts Works · Business Impact of Improper Restriction of Excessive Authentication Attempts · Improper Restriction of Excessive Authentication Attempts Attack Scenario · How to Detect Improper Restriction of Excessive Authentication Attempts · How to Fix Improper Restriction of Excessive Authentication Attempts · Framework-Specific Fixes for Improper Restriction of Excessive Authentication Attempts · How to Ask AI to Check Your Code for Improper Restriction of Excessive Authentication Attempts · Improper Restriction of Excessive Authentication Attempts Best Practices Checklist · Improper Restriction of Excessive Authentication Attempts FAQ · Vulnerabilities Related to Improper Restriction of Excessive Authentication Attempts · References · Scan Your Own Site

Improper Restriction of Excessive Authentication Attempts Overview

What: Improper Restriction of Excessive Authentication Attempts is a vulnerability where an application does not limit the number of failed login attempts.

Why it matters: This allows attackers to perform brute force attacks, potentially gaining access to user accounts and compromising sensitive data.

Where it occurs: In web applications that handle authentication without proper rate limiting or account lockout mechanisms.

Who is affected: Any system with an exposed login interface that does not enforce strict limitations on failed attempts.

How Improper Restriction of Excessive Authentication Attempts Works

Root Cause

The root cause lies in the lack of measures to prevent multiple failed authentication attempts within a short time frame, allowing attackers to perform brute force attacks.

Attack Flow

1. Attacker identifies an exposed login interface.
2. Attacker initiates multiple failed login attempts using different passwords.
3. If no rate limiting or account lockout mechanism is in place, the attacker continues until successful access is gained.

Prerequisites to Exploit

• The application must lack rate limiting and account lockout mechanisms.
• The attacker needs network access to repeatedly attempt logins.

Vulnerable Code

def authenticate(username, password):
    if not validate_credentials(username, password):
        failed_attempts += 1

This code does not implement any mechanism to limit the number of failed login attempts.

Secure Code

def authenticate(username, password):
    if not validate_credentials(username, password):
        failed_attempts += 1
        if failed_attempts >= MAX_FAILED_ATTEMPTS:
            lock_account()
            return False

This code ensures that after a certain number of failed attempts, the account is locked.

Business Impact of Improper Restriction of Excessive Authentication Attempts

Confidentiality: Sensitive data can be exposed through unauthorized access to user accounts. Integrity: Unauthorized users may modify or delete sensitive information. Availability: Account lockouts due to brute force attacks can disrupt legitimate user activity.

• Financial loss from compromised credentials
• Compliance violations due to unauthorized access
• Damage to reputation and trust

Improper Restriction of Excessive Authentication Attempts Attack Scenario

1. Attacker identifies an exposed login interface without rate limiting.
2. The attacker initiates multiple failed login attempts using different passwords.
3. After a series of unsuccessful attempts, the attacker gains access due to lack of account lockout.

How to Detect Improper Restriction of Excessive Authentication Attempts

Manual Testing

• Review authentication logic for rate limiting and account lockout mechanisms.
• Check if there are timeouts or CAPTCHA requirements after failed login attempts.

Automated Scanners (SAST / DAST)

Static analysis can detect the absence of rate limiting, while dynamic testing can simulate brute force attacks to verify their effectiveness.

PenScan Detection

PenScan’s scanner engines such as ZAP and Wapiti can identify vulnerabilities related to improper authentication restrictions.

False Positive Guidance

A false positive may occur if the application has implemented a CAPTCHA or other anti-brute force mechanisms, even if they are not visible in the code.

How to Fix Improper Restriction of Excessive Authentication Attempts

• Implement rate limiting on failed login attempts.
• Lock accounts after a certain number of consecutive failed logins.
• Require users to complete a CAPTCHA challenge after multiple failed attempts.

Framework-Specific Fixes for Improper Restriction of Excessive Authentication Attempts

Python/Django

def authenticate(request):
    if not validate_credentials(request.POST['username'], request.POST['password']):
        failed_attempts = get_failed_attempts(request)
        if failed_attempts >= MAX_FAILED_ATTEMPTS:
            lock_account(request.user)
            return HttpResponse("Account locked due to excessive login attempts.")

Java Spring Boot

@PostMapping("/login")
public ResponseEntity<String> authenticate(@RequestBody LoginRequest request) {
    if (!validateCredentials(request.getUsername(), request.getPassword())) {
        int failedAttempts = getFailedAttempts(request.getUsername());
        if (failedAttempts >= MAX_FAILED_ATTEMPTS) {
            lockAccount(request.getUsername());
            return new ResponseEntity<>("Account locked due to excessive login attempts.", HttpStatus.UNAUTHORIZED);
        }
    }
}

How to Ask AI to Check Your Code for Improper Restriction of Excessive Authentication Attempts

Review the following Python code block for potential CWE-307 Improper Restriction of Excessive Authentication Attempts vulnerabilities and rewrite it using rate limiting:

def authenticate(username, password):
    if not validate_credentials(username, password):
        failed_attempts += 1

Improper Restriction of Excessive Authentication Attempts Best Practices Checklist

✅ Implement a mechanism to limit the number of failed login attempts. ✅ Lock user accounts after a certain number of consecutive failed logins. ✅ Require users to complete a CAPTCHA challenge after multiple failed attempts.

Improper Restriction of Excessive Authentication Attempts FAQ

How does Improper Restriction of Excessive Authentication Attempts work?

An attacker can repeatedly attempt authentication using different passwords until they gain access, exploiting the lack of rate limiting or account lockout mechanisms.

What are the common consequences of Improper Restriction of Excessive Authentication Attempts?

It leads to unauthorized access and compromise of sensitive data through brute force attacks on user accounts.

How can I detect Improper Restriction of Excessive Authentication Attempts in my code?

Review authentication logic for rate limiting, account lockout mechanisms, or timeouts after failed attempts.

What are the best practices to prevent Improper Restriction of Excessive Authentication Attempts?

Implement measures like disconnecting users after a few failed attempts and requiring CAPTCHA verification during login.

How can I use AI to check my code for Improper Restriction of Excessive Authentication Attempts vulnerabilities?

Use an AI coding assistant to review your authentication logic and suggest improvements based on best practices.

What are the related weaknesses to Improper Restriction of Excessive Authentication Attempts?

Weak Authentication (CWE-1390) and Improper Control of Interaction Frequency (CWE-799) are closely related issues.

Vulnerabilities Related to Improper Restriction of Excessive Authentication Attempts

References

• MITRE
• OWASP Top 10:2025 - A07: Authentication Failures
• CAPEC-16, CAPEC-49, CAPEC-560, CAPEC-565, CAPEC-600, CAPEC-652, CAPEC-653
• NVD NIST

Scan Your Own Site

Manual code review catches what you know to look for. An automated scan catches what you didn’t. Scan your own website using PenScan to find Improper Restriction of Excessive Authentication Attempts and other risks before an attacker does.