What is Weak Password Requirements (CWE-521)?

TL;DR: Weak Password Requirements (CWE-521) is a security vulnerability where products do not enforce strong password policies. To mitigate this, implement comprehensive password strength requirements.

What is Weak Password Requirements?

Weak Password Requirements (CWE-521) is a type of authentication vulnerability where products do not enforce strong password policies. As defined by the MITRE Corporation under CWE-521, and classified by the OWASP Foundation under A07:2025 - Authentication Failures.

Quick Summary

Weak Password Requirements occur when a system does not enforce strong password policies, making it easy for attackers to guess user passwords. This vulnerability can lead to unauthorized access and potential privilege escalation within an application. Jump to: Overview · How It Works · Business Impact · Attack Scenario · Detection · Fixes

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

Weak Password Requirements Overview

What

Weak password requirements occur when a system does not enforce strong password policies.

Why it matters

This vulnerability allows attackers to easily guess user passwords, compromising access control and potentially leading to unauthorized access or privilege escalation.

Where it occurs

In web applications that do not implement robust password strength requirements.

Who is affected

Users and organizations whose systems allow weak passwords.

Who is NOT affected

Systems already using strong password policies and enforcement mechanisms.

How Weak Password Requirements Works

Root Cause

The root cause of this vulnerability lies in the absence of a comprehensive password policy that enforces minimum length, complexity, and restrictions on common or contextual passwords.

Attack Flow

1. An attacker identifies a system with weak password requirements.
2. The attacker attempts to guess user passwords using brute-force techniques.
3. If successful, the attacker gains unauthorized access to user accounts.
4. In some cases, the attacker may escalate privileges within the application.

Prerequisites to Exploit

• Weak or non-existent password policies in place.
• User accounts with weak or easily guessable passwords.

Vulnerable Code

def create_user(username, password):
    # No validation for strong password requirements
    user = {'username': username, 'password': password}
    return user

This code does not enforce any strong password policies, making it vulnerable to weak password attacks.

Secure Code

from django.contrib.auth.password_validation import validate_password

def create_user(username, password):
    try:
        validate_password(password)
    except Exception as e:
        raise ValueError("Password is too weak") from e
    
    user = {'username': username, 'password': password}
    return user

This secure code enforces strong password requirements using Django’s validate_password function.

Business Impact of Weak Password Requirements

Confidentiality

Attackers can gain unauthorized access to sensitive data and user accounts.

Integrity

Compromised accounts may be used to modify or manipulate application data.

Availability

In severe cases, attackers may disrupt system availability through privilege escalation attacks.

• Financial Losses: Unauthorized access can result in financial losses due to theft of sensitive information.
• Compliance Violations: Weak password requirements violate security compliance regulations and standards.
• Reputation Damage: Data breaches caused by weak passwords damage an organization’s reputation.

Weak Password Requirements Attack Scenario

1. An attacker identifies a web application with weak password requirements.
2. The attacker uses automated tools to attempt brute-force attacks on user accounts.
3. If successful, the attacker gains unauthorized access and potentially escalates privileges within the system.

How to Detect Weak Password Requirements

Manual Testing

• Check if the system enforces minimum length and complexity for passwords.
• Verify that common or contextual passwords are restricted.
• Test password strength using automated tools like ZAP or Wapiti.

Automated Scanners (SAST / DAST)

Static analysis can detect lack of strong password policies, while dynamic testing simulates brute-force attacks to identify weak passwords.

PenScan Detection

PenScan’s scanner engines such as ZAP and Wapiti can identify systems with insufficient password strength requirements during security assessments.

False Positive Guidance

False positives may occur when a system enforces strong password policies but uses non-standard validation mechanisms. Ensure that the application actually allows weak passwords before marking it as vulnerable.

How to Fix Weak Password Requirements

• Enforce minimum length and complexity for passwords.
• Restrict common or contextual passwords.
• Implement password expiration and reuse restrictions.
• Consider multi-factor authentication (MFA) beyond just strong passwords.

Framework-Specific Fixes for Weak Password Requirements

Python/Django

AUTH_PASSWORD_VALIDATORS = [
    {
        'NAME': 'django.contrib.auth.password_validation.UserAttributeSimilarityValidator',
    },
    {
        'NAME': 'django.contrib.auth.password_validation.MinimumLengthValidator',
        'OPTIONS': {'min_length': 12},
    },
    {
        'NAME': 'django.contrib.auth.password_validation.CommonPasswordValidator',
    },
    {
        'NAME': 'django.contrib.auth.password_validation.NumericPasswordValidator',
    },
]

Java

@Configuration
public class SecurityConfig extends WebSecurityConfigurerAdapter {

    @Override
    protected void configure(AuthenticationManagerBuilder auth) throws Exception {
        auth.userDetailsService(userDetailsService())
            .passwordEncoder(passwordEncoder());
    }

    @Bean
    public PasswordEncoder passwordEncoder() {
        return new BCryptPasswordEncoder();
    }
}

Node.js

const bcrypt = require('bcrypt');

function createHashedPassword(password) {
    const saltRounds = 10;
    return bcrypt.hashSync(password, saltRounds);
}

How to Ask AI to Check Your Code for Weak Password Requirements

Weak Password Requirements Best Practices Checklist

✅ Enforce minimum length and complexity requirements. ✅ Restrict common or contextual passwords. ✅ Implement password expiration policies. ✅ Consider multi-factor authentication (MFA) beyond just strong passwords.

Weak Password Requirements FAQ

How do I define weak password requirements?

Weak password requirements occur when a system does not enforce strong password policies, making it easier for attackers to guess user passwords.

What are the consequences of weak password requirements?

Attackers can easily gain unauthorized access to user accounts and potentially escalate privileges within an application.

How do I detect weak password requirements in my code?

Review your authentication mechanisms and check if they enforce minimum length, complexity, and other strong password policies.

What are some best practices for fixing weak password requirements?

Implement a robust password policy that includes minimum length, character diversity, and restrictions on common or contextual passwords.

How does PenScan detect weak password requirements?

PenScan’s automated scanners can identify systems with insufficient password strength requirements during security assessments.

Can you show an example of secure password handling code?

Use a framework-specific mechanism to enforce strong password policies, such as Django’s AUTH_PASSWORD_VALIDATORS setting.

How do I prevent weak passwords in my application?

Enforce a comprehensive password policy that includes complexity requirements and regular updates.

Vulnerabilities Related to Weak Password Requirements

References

• MITRE: CWE-521
• OWASP Top 10: A07:2025 - Authentication Failures
• CAPEC: CAPEC-112, CAPEC-16, CAPEC-49, CAPEC-509, CAPEC-55, CAPEC-555, CAPEC-561, CAPEC-565, CAPEC-70
• NVD: NIST National Vulnerability Database

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 Weak Password Requirements and other risks before an attacker does.