JWT Expiration Bypass Scanner
Identifies JWT implementations that don't properly validate expiration.
What is JWT Expiration Bypass?
JWT Expiration Bypass occurs when applications fail to properly validate the exp (expiration), nbf (not before), or iat (issued at) claims. Attackers can use expired tokens indefinitely, modify timestamps to extend validity, or exploit time synchronization issues between servers.
Why is This Important?
Expiration is a critical security control that limits the damage from token theft. If expiration isn't enforced, stolen tokens remain valid forever, refresh token rotation becomes meaningless, and session termination becomes impossible. This extends the window for token abuse from minutes to indefinite.
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
What expiration-related claims should be validated?
exp (expiration time): reject if current time > exp. nbf (not before): reject if current time < nbf. iat (issued at): consider rejecting tokens too old even within exp. Each should have a small clock skew tolerance (typically 30-60 seconds).
How do attackers exploit weak expiration checks?
Attackers: remove the exp claim entirely (if not required), set exp far in the future, modify exp while exploiting algorithm confusion, exploit large clock skew tolerances, or find servers with incorrect system time.
Why do some applications skip expiration validation?
Developers sometimes skip validation during development and forget to enable it, use JWT libraries with lax defaults, misconfigure validation options, or intentionally skip it not understanding the security implications.
How do I properly implement expiration validation?
Configure your JWT library to require and validate exp, set short token lifetimes (15 minutes for access tokens), use refresh tokens for longer sessions, implement token revocation for logout, maintain accurate server time via NTP, and use minimal clock skew tolerance.
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