Date published: 2017-08-24T12:29:00.197-04:00
Date last modified: 2017-11-03T21:29:33.413-04:00
CVSS Score: 5.0
Principal attack vector: NETWORK
Reference URL: http://www.debian.org/security/2017/dsa-3979
Summary: 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.