# 2FA Bypass Using a Brute Force Attack
## Overview
The Nagios Fusion application (version 2024R1.2 and 2024R2) is vulnerable to a Brute-Force attack on its Two-Factor Authentication (2FA) mechanism. Specifically, the 2FA implementation does not adequately enforce rate-limiting or account lockout mechanisms, allowing an attacker to bypass 2FA by repeatedly guessing the One-Time Password (OTP).
**The following issues were observed:**
- **Lack of Rate-Limiting**: The 2FA endpoint does not limit the number of OTP submission attempts.
- **Weak Lockout Policy**: No account lockout is triggered after repeated failed OTP attempts, enabling brute-force attacks to succeed.
- **Potential for Unauthorized Access**: With sufficient computational resources, an attacker could bypass 2FA and gain unauthorized access to sensitive accounts, including administrator accounts.
*This vulnerability stems from the absence of proper defences against brute-force attacks, rendering the 2FA mechanism ineffective against targeted attacks.*
## Severity
- **Severity**: High
- **CWE**: CWE-307 (primary); CWE-287 (secondary)
- **CVSS Score (v3.0)**: 7.6 High
- **CVSS Vector**: AV:A/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:L
## Affected Components
- 2FA Verification Endpoint (e.g., /verify-otp)
- Authentication Middleware
- Session Issuance Service
- Rate Limiting / Anti-Automation Controls
## Affected Vendor/Product
- **Product Name**- Nagios Fusion
- **Affected Version**: 2024R1.2 and 2024R2
- **Fixed Version**: 2024R2.1
## Summary of the Issue
**What Happens:**
1. User attempts login with valid username and password.
2. System prompts for OTP from authenticator app/SMS/email.
3. Attacker scripts automated requests to /verify-otp endpoint.
4. Due to lack of rate limiting and lockout, attacker can attempt unlimited guesses.
5. Within feasible time, attacker predicts correct OTP and bypasses 2FA.
**Security Posture Gap**:
2FA is meant to increase entropy and reduce brute-force feasibility. Without proper anti-automation controls, OTP becomes brute-forceable, negating the second factor.
**Abuse Scenarios**:
- Automated credential stuffing + brute-force OTP to achieve mass account takeover.
- Targeted attack against high-value accounts where password was phished or leaked.
## Mitigation Recommendations
- Enforce strict rate limiting per account/IP/device for OTP attempts.
- Lock account after N failed OTP attempts and require re-authentication.
- Introduce back-off delays (e.g., exponential) on repeated failures.
## Disclosure Timeline
- **[05-01-2025]**: Vulnerability discovered
- **[05-01-2025]**: Reported to vendor
- **[10-01-2025]**: Vendor verified the vulnerability
- **[23-07-2025]**: Vendor patched the vulnerability with a new release
- **[16-08-2025]**: Apply For CVE
- **[23-10-2025]**: Assign CVE
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📌 *This repository is intended solely for vulnerability reporting and CVE reference.*
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