Nov json-jwt version >= 0.5.0 && < 1.9.4 contains a CWE-347: Improper Verification of Cryptographic Signature vulnerability in Decryption of AES-GCM encrypted JSON Web Tokens that can result in Attacker can forge a authentication tag. This attack appear to be exploitable via network connectivity. This vulnerability appears to have been fixed in 1.9.4 and later.
Debian Linux Security Advisory 4283-1 - It was discovered that ruby-json-jwt, a Ruby implementation of JSON web tokens performed insufficient validation of GCM auth tags.