2FA Bypass - Race Condition Scanner
Identifies 2FA race conditions allowing code reuse.
What is 2FA Bypass - Race Condition?
2FA Race Condition Bypass occurs when the two-factor authentication verification process has timing vulnerabilities. Attackers can send multiple parallel requests with the same OTP code, and due to race conditions in validation or session handling, multiple requests succeed before the code is invalidated.
Why is This Important?
Race conditions in 2FA can allow a single stolen OTP to be used multiple times across different sessions. This is especially dangerous with time-based OTP (TOTP) where attackers have a 30-second window. A single intercepted code can create multiple authenticated sessions.
How It Works
1. Auth Flow Analysis
Maps authentication mechanisms including login, registration, password reset, and session management flows.
2. Security Testing
Tests for authentication bypasses, weak credentials, session flaws, and token vulnerabilities.
3. Access Verification
Validates findings by demonstrating unauthorized access or privilege escalation paths.
Key Capabilities
Comprehensive authentication security testing to protect user accounts and prevent unauthorized access.
- Complete authentication flow analysis
- Token and session security validation
- Password policy and brute-force testing
- Multi-factor authentication bypass detection
- OAuth, SAML, and JWT security assessment
Frequently Asked Questions
How does the 2FA race condition attack work?
Attacker obtains a valid OTP (phishing, SIM swap, etc.), sends many parallel requests with that code before any completes, the server validates each request against the still-valid code, and multiple sessions get authenticated. The code is only invalidated after the first response, too late for parallel requests.
What types of 2FA are vulnerable?
TOTP (Google Authenticator style) is most commonly vulnerable due to the 30-second validity window. SMS codes with longer windows are also at risk. Hardware tokens with event counters are less vulnerable but can still have race issues in session creation.
What server-side issues enable this?
Issues include: code validation and invalidation not being atomic, session creation happening before code invalidation, database transactions not properly isolating validation, caching of valid codes, and load balancer distribution to multiple servers with separate state.
How do I prevent 2FA race conditions?
Use atomic operations for code validation and invalidation, implement database-level locking during validation, use transaction isolation, add nonce or request ID checking, implement short code lifetimes, use hardware tokens with strict counters, and test with parallel request tools.
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