1. Introduction
The Login Form Bruteforced vulnerability occurs when an attacker attempts multiple login attempts with various credentials on a web application’s login form. This can lead to unauthorized access if default or weak passwords are used. It affects any web application with a login feature, particularly those without sufficient account protection measures. Successful exploitation could compromise confidentiality, integrity and availability of the application and its data.
2. Technical Explanation
The vulnerability arises from applications allowing excessive login attempts without rate limiting or account lockout mechanisms, combined with weak password policies. Attackers exploit this by using automated tools to try common usernames and passwords against the login form. The scanner successfully authenticated on the target web application by using predictable credentials on its login form.
- Root cause: Lack of a complex password policy and insufficient protection against brute-force attacks.
- Exploit mechanism: An attacker uses tools like Hydra or Burp Suite to automate credential guessing attempts against the login form. For example, an attacker could use a wordlist containing common passwords to attempt logins repeatedly until a valid account is found.
- Scope: Web applications with publicly accessible login forms that do not enforce strong password policies and rate limiting.
3. Detection and Assessment
To confirm vulnerability, check for weak or default accounts and monitor login attempts.
- Quick checks: Check the application’s configuration files for any hardcoded credentials or default account settings.
- Scanning: Use vulnerability scanners like OWASP ZAP or Burp Suite to perform brute-force attacks against the login form (with permission).
- Logs and evidence: Examine web server logs for failed login attempts originating from a single IP address within a short timeframe. Look for patterns indicating automated attacks.
# Example command placeholder:
# Check user accounts with weak passwords using a script or tool
4. Solution / Remediation Steps
Implement strong password policies and account protection measures to prevent brute-force attacks.
4.1 Preparation
- Ensure you have access to modify the application’s authentication settings and database. Roll back plan: Restore from backup if issues occur.
- Change window needs may apply for production systems; approval from security team is recommended.
4.2 Implementation
- Step 1: Implement a complex password policy requiring minimum length, uppercase/lowercase letters, numbers, and special characters.
- Step 3: Implement rate limiting to restrict the number of login attempts from a single IP address within a given timeframe.
- Step 4: Consider implementing multi-factor authentication (MFA) for increased security.
4.3 Config or Code Example
Before
# No password complexity requirements configured
After
# Password policy configured with minimum length, character types, and account lockout settings.
# Example (Apache .htaccess):
#
# Require all granted
# LimitRequestBody 1024 # Limit request size to prevent large payloads
#
4.4 Security Practices Relevant to This Vulnerability
List only practices that directly address this vulnerability type. Use neutral wording and examples instead of fixed advice. For example: least privilege, input validation, safe defaults, secure headers, patch cadence. If a practice does not apply, do not include it.
- Least privilege: Limit user access to only the necessary resources to reduce the impact if an account is compromised.
- Input validation: Validate all user inputs on both client and server-side to prevent malicious data from being processed.
- Secure defaults: Configure secure default settings for accounts and authentication mechanisms.
4.5 Automation (Optional)
# Example PowerShell script to check password policy strength:
# Get-ADDefaultDomainPasswordPolicy | Select-Object PasswordHistoryCount, MinimumPasswordLength, PasswordComplexityEnabled
5. Verification / Validation
Confirm the fix by testing the new password policy and account lockout features.
- Post-fix check: Attempt to create an account with a weak password; it should be rejected.
- Smoke test: Verify that legitimate users can still log in successfully with strong passwords.
- Monitoring: Monitor web server logs for account lockout events and excessive login attempts from single IP addresses.
# Post-fix command and expected output:
# Attempt to create a user with password "password123" - should fail due to policy restrictions.
6. Preventive Measures and Monitoring
Suggest only measures that are relevant to the vulnerability type. Use “for example” to keep advice conditional, not prescriptive.
- Baselines: Update security baselines or policies to include strong password requirements and account lockout settings (for example, CIS control 5).
- Asset and patch process: Regularly review user accounts and passwords for compliance with the defined security policies.
7. Risks, Side Effects, and Roll Back
- Risk or side effect 1: Users may experience difficulty logging in if they are unaware of the new password policy requirements. Provide clear communication and support resources.
- Risk or side effect 2: Account lockout can disrupt legitimate users; ensure a self-service password reset mechanism is available.
- Roll back: Restore the previous application configuration from backup. Revert any changes made to authentication settings.
8. References and Resources
- Vendor advisory or bulletin: N/A – depends on the specific application vendor.
- NVD or CVE entry: N/A – This is a common vulnerability pattern, not a specific CVE.
- Product or platform documentation relevant to the fix: OWASP Authentication Cheat Sheet