Authentication Failures in OWASP Top 10 (2025)

Authentication is one of the most critical security mechanisms in any web application. It ensures that only legitimate users can access protected resources and perform authorized actions. Authentication Failures occur when weaknesses in the authentication or session management process allow attackers to impersonate valid users, gain unauthorized access, or compromise user accounts.

In the OWASP Top 10 (2025), Authentication Failures (A07) remain a significant security concern because compromised authentication mechanisms often lead directly to account takeover, data breaches, and unauthorized access to sensitive systems.

What Are Authentication Failures?

Authentication Failures arise when an application incorrectly verifies the identity of users or fails to properly manage authentication sessions. These weaknesses allow attackers to bypass login controls, steal credentials, hijack sessions, or gain access to accounts they do not own.

In simple terms, if an unauthorized or unregistered user can trick the application into treating them as a legitimate user, the application may be vulnerable to an Authentication Failure.

Common Causes of Authentication Failures

An application may be vulnerable to Authentication Failures if it contains one or more of the following weaknesses:

1. Credential Stuffing Attacks

Credential stuffing occurs when attackers use lists of usernames and passwords obtained from previous data breaches and automatically test them against application login pages.

If the application lacks protection mechanisms such as account lockout, rate limiting, CAPTCHA, or MFA, attackers may successfully gain access to user accounts.

2. Brute Force Attacks

Applications that allow unlimited login attempts are vulnerable to brute force attacks. Attackers can repeatedly try different password combinations until the correct credentials are discovered.

3. Weak or Default Passwords

Allowing simple passwords such as: password123, admin123, welcome, 12345678

or default vendor-supplied passwords significantly increases the risk of account compromise.

4. Weak Password Recovery Mechanisms

Password reset processes should be secure and difficult to abuse.

Applications are vulnerable when password recovery relies on easily guessable security questions .

Attackers may discover this information through social media or public sources.

5. Insecure Password Storage

Passwords should never be stored in plaintext or protected using weak encryption methods.

If attackers gain database access and passwords are stored insecurely, they can quickly recover user credentials and perform further attacks.

6. Weak Session Management

Authentication does not end after login. Session management is equally important.

Security issues may arise when:

• Session identifiers are predictable.
• Session cookies can be reused.
• Sessions remain active after logout.
• Session tokens are not regenerated after authentication.

These weaknesses can lead to session hijacking and unauthorized access.

7. Missing or Weak Multi-Factor Authentication (MFA)

Applications relying solely on usernames and passwords provide attackers with a single barrier to compromise.

Implementing MFA significantly reduces the risk of account takeover, even when passwords are stolen.

Example of an Authentication Failure

Consider a login page that does not implement account lockout, rate limiting, CAPTCHA, or MFA.

An attacker uses an automated tool to test thousands of username and password combinations against the login form. Because the application places no restrictions on repeated login attempts, the attacker eventually discovers valid credentials and gains unauthorized access to a user account.

This scenario represents a classic Authentication Failure and demonstrates how weak authentication controls can result in account compromise.

Commonly Mapped CWEs

Authentication Failures are frequently associated with the following Common Weakness Enumerations (CWEs):

Prevention of Authentication Failures

Organizations should implement the following security controls to reduce authentication-related risks:

Implement Multi-Factor Authentication (MFA)

Require a second authentication factor such as:

• One-Time Passwords (OTP)
• Authenticator applications
• Hardware security keys

MFA significantly reduces the effectiveness of credential stuffing and password-based attacks.

Protect Against Brute Force Attacks

Use:

• Account lockout policies
• Login rate limiting
• CAPTCHA

These mechanisms help prevent automated login attempts.

Enforce Strong Password Policies

Require passwords that:

• Are at least 8–12 characters long
• Contain uppercase and lowercase letters
• Include numbers and special characters
• Are not found in breached-password databases

Weak and default passwords should never be allowed.

Secure Password Reset Functionality

Password recovery mechanisms should:

• Use secure email verification
• Require MFA when possible
• Generate time-limited reset tokens
• Avoid knowledge-based security questions

Secure Password Storage

Passwords should be stored using strong one-way hashing algorithms.

Plaintext password storage should never be used.

Implement Secure Session Management

Applications should:

• Generate random session identifiers
• Use Secure and HttpOnly cookie attributes
• Regenerate session IDs after authentication
• Invalidate sessions immediately after logout
• Configure appropriate session timeouts

These controls help prevent session fixation and session hijacking attacks.

Use Generic Login Error Messages

Avoid revealing whether a username or password is incorrect.

Instead of displaying:

• “User does not exist”
• “Password is incorrect”

Display a generic message such as:

“Invalid username or password.”

This reduces user enumeration risks.

Authentication Failures remain one of the most dangerous security weaknesses identified in the OWASP Top 10 (2025). Weak passwords, credential stuffing vulnerabilities, insecure session management, poor password recovery processes, and the absence of MFA can all expose applications to account compromise and unauthorized access.

Organizations should adopt strong authentication mechanisms, secure session management practices, robust password policies, and multi-factor authentication to protect user accounts and reduce the risk of authentication-based attacks.

For more information, visit the official OWASP Top 10 project at https://owasp.org/www-project-top-ten/.