jwt-scala 1.2.2 and earlier fails to verify token signatures correctly which may lead to an attacker being able to pass specially crafted JWT data as a correctly signed token.

In PyJWT 1.5.0 and below the `invalid_strings` check in `HMACAlgorithm.prepare_key` does not account for all PEM encoded public keys. Specifically, the PKCS1 PEM encoded format would be allowed because it is prefaced with the string `-----BEGIN RSA PUBLIC KEY-----` which is not accounted for. This enables symmetric/asymmetric key confusion attacks against users using the PKCS1 PEM encoded public keys, which would allow an attacker to craft JWTs from scratch.

Nimbus JOSE+JWT before 4.39 proceeds improperly after detection of an invalid HMAC in authenticated AES-CBC decryption, which allows attackers to conduct a padding oracle attack.

Nimbus JOSE+JWT before 4.36 proceeds with ECKey construction without ensuring that the public x and y coordinates are on the specified curve, which allows attackers to conduct an Invalid Curve Attack in environments where the JCE provider lacks the applicable curve validation.

In Nimbus JOSE+JWT before 4.39, there is no integer-overflow check when converting length values from bytes to bits, which allows attackers to conduct HMAC bypass attacks by shifting Additional Authenticated Data (AAD) and ciphertext so that different plaintext is obtained for the same HMAC.

The verify function in Encryption/Symmetric.php in Malcolm Fell jwt before 1.0.3 does not use a timing-safe function for hash comparison, which allows attackers to spoof signatures via a timing attack.

JWT.php in F21 JWT before 2.0 allows remote attackers to bypass signature verification via crafted tokens.