CVE-2016-9243: Canonical Ubuntu Linux

High severity, CVSS 7.5. EPSS: 3.5% chance of exploitation in the next 30 days.

HKDF in cryptography before 1.5.2 returns an empty byte-string if used with a length less than algorithm.digest_size.

Affected products

• Canonical Ubuntu Linux: version 16.04 only; version 16.10 only
• Cryptography.io Cryptography: up to and including 1.5.2
• Fedoraproject Fedora: version 23 only; version 24 only; version 25 only

Published 2017-03-27. Last modified 2026-06-17.