OnlyFm252
Microsoft Windows

CVE-2020-17049 — Kerberos KDC Security Feature Bypass Vulnerability

Important CVSS 6.6 EPSS 0.13794 2020-11 archive

Executive Summary

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.

Overview

6.6
CVSS MEDIUM
Important
MS Severity
Not Exploited
MS Exploit Status
Less Likely
MS Exploit Likelihood
Category Security Feature Bypass
Released Nov 10 2020
Last Updated Nov 10 2020
Publicly Disclosed No
CISA KEV Not Listed
Known Exploits None Known
EPSS Score 0.13794 — 0.96033 percentile
NVD CVSS 6.6 MEDIUM — matches MSRC

CVSS Vector

CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C
ATTACK VECTOR
Network
ATTACK COMPLEXITY
High
PRIVILEGES REQUIRED
High
USER INTERACTION
None
SCOPE
Unchanged
CONFIDENTIALITY
High
INTEGRITY
High
AVAILABILITY
High
EXPLOIT CODE MATURITY
Unproven
REMEDIATION LEVEL
Official Fix
REPORT CONFIDENCE
Confirmed
Temporal Score: 5.8

EPSS Score

0.13794
probability of exploitation in the next 30 days
0.96033 percentile - updated 2026-06-21
View on FIRST.org

Affected Products

8 affected products
Product KB Article Severity Impact Restart Required
Windows Server 2008 for 32-bit Systems Service Pack 2 5004305 (Monthly Rollup) 5004299 (Security Only) Important Security Feature Bypass 5004955 Base: 6.6 Temporal: 5.8 Vector: CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C 6.0.6003.21167 Yes 5004305 5004299 Windows Server 2008 for 32-bit Systems Service Pack 2 (Server Core installation) 5004305 (Monthly Rollup) 5004299 (Security Only) Important Security Feature Bypass 5004955 Base: 6.6 Temporal: 5.8 Vector: CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C 6.0.6003.21167 Yes 5004305 5004299 Windows Server 2008 for x64-based Systems Service Pack 2 5004305 (Monthly Rollup) 5004299 (Security Only) Important Security Feature Bypass 5004955 Base: 6.6 Temporal: 5.8 Vector: CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C 6.0.6003.21167 Yes 5004305 5004299 Windows Server 2008 for x64-based Systems Service Pack 2 (Server Core installation) 5004305 (Monthly Rollup) 5004299 (Security Only) Important Security Feature Bypass 5004955 Base: 6.6 Temporal: 5.8 Vector: CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C 6.0.6003.21167 Yes 5004305 5004299 Windows Server 2008 R2 for x64-based Systems Service Pack 1 5004289 (Monthly Rollup) 5004307 (Security Only) Important Security Feature Bypass 5004953 Base: 6.6 Temporal: 5.8 Vector: CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C 6.1.7601.25661 Yes 5004289 5004307 Windows Server 2008 R2 for x64-based Systems Service Pack 1 (Server Core installation) 5004289 (Monthly Rollup) 5004307 (Security Only) Important Security Feature Bypass 5004953 Base: 6.6 Temporal: 5.8 Vector: CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C 6.1.7601.25661 Yes 5004289 5004307 Windows Server 2012 5004294 (Monthly Rollup) 5004302 (Security Only) Important Security Feature Bypass 5004956 Base: 6.6 Temporal: 5.8 Vector: CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C 6.2.9200.23409 Yes 5004294 5004302 Windows Server 2012 (Server Core installation) 5004294 (Monthly Rollup) 5004302 (Security Only) Important Security Feature Bypass 5004956 Base: 6.6 Temporal: 5.8 Vector: CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C 6.2.9200.23409 Yes 5004294 5004302 Windows Server 2012 R2 5004298 (Monthly Rollup) 5004285 (Security Only) Important Security Feature Bypass 5004954 Base: 6.6 Temporal: 5.8 Vector: CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C 6.3.9600.20069 Yes 5004298 5004285 Windows Server 2012 R2 (Server Core installation) 5004298 (Monthly Rollup) 5004285 (Security Only) Important Security Feature Bypass 5004954 Base: 6.6 Temporal: 5.8 Vector: CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C 6.3.9600.20069 Yes 5004298 5004285 Windows Server 2016 5004238 (Security Update) Important Security Feature Bypass Yes
Windows Server 2016 (Server Core installation) 5004238 (Security Update) Important Security Feature Bypass Yes
Windows Server 2019 5004244 (Security Update) Important Security Feature Bypass Yes
Windows Server 2019 (Server Core installation) 5004244 (Security Update) Important Security Feature Bypass Yes
Windows Server, version 1903 (Server Core installation) 4592449 (Security Update) Important Security Feature Bypass Yes
Windows Server, version 1909 (Server Core installation) 5001337 (Security Update) Important Security Feature Bypass Yes
Windows Server, version 2004 (Server Core installation) 5004237 (Security Update) Important Security Feature Bypass Yes
Windows Server, version 20H2 (Server Core Installation) 5004237 (Security Update) Important Security Feature Bypass Yes

Patches

5 patches
Article Type Restart
5004238 Security Update Yes
5004244 Security Update Yes
4592449 Security Update Yes
5001337 Security Update Yes
5004237 Security Update Yes

Known Exploits

Acknowledgments

NetSPI

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