Kerberos KDC Security Feature Bypass Vulnerability

2020-11-1008:00:00

Microsoft

msrc.microsoft.com

225

9 High

CVSS2

Attack Vector

NETWORK

Attack Complexity

LOW

Authentication

SINGLE

Confidentiality Impact

COMPLETE

Integrity Impact

COMPLETE

Availability Impact

COMPLETE

AV:N/AC:L/Au:S/C:C/I:C/A:C

6.6 Medium

CVSS3

Attack Vector

NETWORK

Attack Complexity

HIGH

Privileges Required

HIGH

User Interaction

NONE

Scope

UNCHANGED

Confidentiality Impact

HIGH

Integrity Impact

HIGH

Availability Impact

HIGH

CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H

0.027 Low

EPSS

Percentile

90.6%

JSON

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.