CVE-2019-14870: Canonical Ubuntu Linux

Medium severity, CVSS 5.4. EPSS: 2.7% chance of exploitation in the next 30 days.

All Samba versions 4.x.x before 4.9.17, 4.10.x before 4.10.11 and 4.11.x before 4.11.3 have an issue, where the S4U (MS-SFU) Kerberos delegation model includes a feature allowing for a subset of clients to be opted out of constrained delegation in any way, either S4U2Self or regular Kerberos authentication, by forcing all tickets for these clients to be non-forwardable. In AD this is implemented by a user attribute delegation_not_allowed (aka not-delegated), which translates to disallow-forwardable. However the Samba AD DC does not do that for S4U2Self and does set the forwardable flag even if the impersonated client has the not-delegated flag set.

Affected products

• Canonical Ubuntu Linux: version 14.04 only; version 16.04 only; version 18.04 only; version 19.04 only; version 19.10 only
• Debian Debian Linux: version 9.0 only; version 10.0 only
• Fedoraproject Fedora: version 30 only; version 31 only
• Opensuse Leap: version 15.1 only
• Samba Samba: from 4.0.0, before 4.9.17 (fixed in 4.9.17); from 4.10.0, before 4.10.11 (fixed in 4.10.11); from 4.11.0, before 4.11.3 (fixed in 4.11.3)

Published 2019-12-10. Last modified 2026-06-17.