JWT Authentication in Practice: Security Pitfalls and Best Practices

Common Security Pitfalls

Algorithm None Attack: Some JWT libraries allow the "none" algorithm, enabling attackers to craft unsigned tokens that bypass verification. Key Confusion Attack: When systems support both RSA and HMAC, attackers may use the public key as an HMAC secret. Never-Expiring Tokens: JWTs without reasonable expiration times are equivalent to permanent credentials.

Best Practices

Use asymmetric encryption (RS256) over symmetric (HS256); set reasonable expiration times (15-30 minutes recommended); implement token refresh mechanisms; use JTI (JWT ID) to prevent replay attacks; never store sensitive data in the payload.

Refresh Token Strategy

Adopt a dual-token approach: short-lived Access Token (15 min) + long-lived Refresh Token (7 days), with the Refresh Token stored in an HttpOnly cookie.

---

Small team, big output. iDev builds web apps, AI solutions and custom systems with startup speed and enterprise quality. Based in Malaysia, serving Southeast Asia. Free consultation.