CVE-2018-10903: Canonical Ubuntu Linux

High severity, CVSS 7.5. EPSS: 3.2% chance of exploitation in the next 30 days.

A flaw was found in python-cryptography versions between >=1.9.0 and <2.3. The finalize_with_tag API did not enforce a minimum tag length. If a user did not validate the input length prior to passing it to finalize_with_tag 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.

Affected products

• Canonical Ubuntu Linux: version 18.04 only
• Cryptography Python-Cryptography: from 1.9.0, before 2.3 (fixed in 2.3)
• Red Hat Openstack: version 13 only

Published 2018-07-30. Last modified 2026-06-17.