CVE-2020-17049: Microsoft Windows Server 2012

Medium severity, CVSS 6.6. EPSS: 13.8% chance of exploitation in the next 30 days.

A security feature bypass vulnerability exists in the way Key Distribution Center (KDC) determines if a service ticket can be used for delegation via Kerberos Constrained Delegation (KCD). To exploit the vulnerability, a compromised service that is configured to use KCD could tamper with a service ticket that is not valid for delegation to force the KDC to accept it. The update addresses this vulnerability by changing how the KDC validates service tickets used with KCD.

Affected products

• Microsoft Windows Server 2012: any version; version r2 only
• Microsoft Windows Server 2016: affected versions not specified; version 20h2 only; version 1903 only; version 1909 only; version 2004 only
• Microsoft Windows Server 2019: affected versions not specified
• Samba Samba: from 4.1.0, before 4.13.13 (fixed in 4.13.13); from 4.14.0, before 4.14.9 (fixed in 4.14.9); from 4.15.0, before 4.15.1 (fixed in 4.15.1)

Published 2020-11-11. Last modified 2026-06-17.