CVE-2019-17023: Canonical Ubuntu Linux

Medium severity, CVSS 6.5. EPSS: 1.3% chance of exploitation in the next 30 days.

After a HelloRetryRequest has been sent, the client may negotiate a lower protocol that TLS 1.3, resulting in an invalid state transition in the TLS State Machine. If the client gets into this state, incoming Application Data records will be ignored. This vulnerability affects Firefox < 72.

Affected products

• Canonical Ubuntu Linux: version 16.04 only; version 18.04 only; version 19.04 only; version 19.10 only; version 20.04 only
• Debian Debian Linux: version 10.0 only
• Mozilla Firefox: before 72.0 (fixed in 72.0)

Published 2020-01-08. Last modified 2026-06-17.