JWT authentication is one of those things that looks simple until you see the CVEs. Algorithm confusion, weak secrets, missing expiry — most JWT vulnerabilities aren't exotic. They come from implementation shortcuts that seemed harmless at the time. This article covers how to do JWT auth correctly in Go Fiber, including token generation, validation, and the refresh flow.
Why JWT Auth Fails in Practice
The spec is fine. The failures happen in implementation:
Algorithm confusion attacks: if you don't explicitly lock the expected signing algorithm, an attacker can switch from RS256 to HS256 and sign tokens with your public key
Weak secrets: HS256 with a short or predictable secret is brute-forceable — the JWT spec recommends 256 bits (32 bytes) minimum
