The python-cryptography and python-cryptography-vectors packages have been updated to version 2.3.1 and fixes the following security issue:
The finalizewithtag API did not enforce a minimum tag length. If a user did not validate the input length prior to passing it to finalizewithtag an attacker could craft an invalid payload with a shortened tag (e.g. 1 byte) such that they would have a 1 in 256 chance of passing the MAC check. GCM tag forgeries can cause key leakage (CVE-2018-10903).