The Ultimate Guide to JWT Vulnerabilities and Attacks (with Exploitation Examples)

JWT vulnerabilities pose serious security risks in modern web applications. Common attacks include signature bypass, algorithm confusion (switching from RS256 to HS256), weak secret brute-forcing, and injection attacks through header parameters like 'kid' and 'jku'. The guide covers exploitation techniques for each vulnerability type, from trivial signature removal to sophisticated ECDSA psychic signature attacks. Key defense strategies include strict algorithm validation, secure key management, input sanitization, and proper signature verification implementation.