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Fencer Vulns
high 7.2

CVE-2020-17049 in the critical feed json

Kerberos KDC Security Feature Bypass Vulnerability

published 2020-11-11 5 y ago modified 2026-06-17 4 mo ago also EUVD-2020-9005

cvss
7.2
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
13.8%
EPSS 13.8% chance of exploitation in 30 days, percentile 96%
public exploits
0
none known

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.

Patch / fix

  • Microsoft Windows Server 2019 10.0.17763.2061
  • Microsoft Windows Server 2019 (Server Core installation) 10.0.17763.2061
  • Microsoft Windows Server version 2004 10.0.19041.1110
  • Microsoft Windows Server 2016 10.0.14393.4530
  • Microsoft Windows Server 2016 (Server Core installation) 10.0.14393.4530
  • Microsoft Windows Server 2008 Service Pack 2 6.0.6003.21167
  • Microsoft Windows Server 2008 Service Pack 2 (Server Core installation) 6.0.6003.21167
  • Microsoft Windows Server 2008 Service Pack 2 6.0.6003.21167
  • Microsoft Windows Server 2008 R2 Service Pack 1 6.1.7601.25661
  • Microsoft Windows Server 2008 R2 Service Pack 1 (Server Core installation) 6.1.7601.25661
  • Microsoft Windows Server 2012 6.2.9200.23409
  • Microsoft Windows Server 2012 (Server Core installation) 6.2.9200.23409
  • Microsoft Windows Server 2012 R2 6.3.9600.20069
  • Microsoft Windows Server 2012 R2 (Server Core installation) 6.3.9600.20069
  • Microsoft Windows Server version 20H2 10.0.19041.1110
  • ipa RHEL 8 4.9.12-11.module+el8.9.0+20824+f2605038
  • pyusb RHEL 8 1.0.0-9.1.module+el8.9.0+18911+94941f82
  • softhsm RHEL 8 2.6.0-5.module+el8.9.0+18911+94941f82
  • custodia RHEL 8 0.6.0-3.module+el8.9.0+18911+94941f82
  • slapi-nis RHEL 8 0.60.0-4.module+el8.9.0+20420+fef9eb45
  • ipa-client RHEL 8 4.9.12-11.module+el8.9.0+20824+f2605038
  • ipa-common RHEL 8 4.9.12-11.module+el8.9.0+20824+f2605038
  • ipa-server RHEL 8 4.9.12-11.module+el8.9.0+20824+f2605038

red hat advisories RHSA-2024:0137RHSA-2024:0139RHSA-2024:0143RHSA-2023:2570

  • samba Enterprise Storage 7 4.13.13+git.545.5897c2d94f3-3.12.1
  • ldb Enterprise Storage 7 2.2.2-4.6.1

suse advisories SUSE-SU-2022:0361-1

  • python-impacket openSUSE Tumbleweed 0.13.1-1.2
  • samba openSUSE Tumbleweed 4.15.2+git.193.a4d6307f1fd-1.1

opensuse advisories openSUSE-SU-2026:12011-1openSUSE-SU-2024:11631-1

  • softhsm AlmaLinux 8 2.6.0-5.module_el8.6.0+2881+2f24dc92
  • softhsm AlmaLinux 8 2.6.0-5.module_el8.6.0+3031+2f24dc92
  • custodia AlmaLinux 8 0.6.0-3.module_el8.6.0+2881+2f24dc92
  • slapi-nis AlmaLinux 8 0.60.0-4.module_el8.9.0+3682+f63caf3e.alma.1
  • ipa-client AlmaLinux 8 4.9.12-11.module_el8.9.0+3715+e4197dc9.alma.1
  • ipa-common AlmaLinux 8 4.9.12-11.module_el8.9.0+3715+e4197dc9.alma.1
  • ipa-server AlmaLinux 8 4.9.12-11.module_el8.9.0+3715+e4197dc9.alma.1
  • opendnssec AlmaLinux 8 2.1.7-1.module_el8.6.0+2881+2f24dc92

almalinux advisories ALSA-2024:0143ALSA-2023:2570

  • pyusb Rocky Linux 8 1.0.0-9.1.module+el8.9.0+1371+ffa84eb9
  • pyusb Rocky Linux 8 1.0.0-9.1.module+el8.9.0+1372+09f67869
  • softhsm Rocky Linux 8 2.6.0-5.module+el8.9.0+1371+ffa84eb9
  • custodia Rocky Linux 8 0.6.0-3.module+el8.9.0+1371+ffa84eb9
  • slapi-nis Rocky Linux 8 0.60.0-4.module+el8.9.0+1573+39ab85f4
  • opendnssec Rocky Linux 8 2.1.7-1.module+el8.9.0+1371+ffa84eb9
  • python-qrcode Rocky Linux 8 5.1-12.module+el8.9.0+1371+ffa84eb9
  • python-qrcode Rocky Linux 8 5.1-12.module+el8.9.0+1372+09f67869

rocky linux advisories RLSA-2024:0143

  • samba Azure Linux 3.0 4.18.3-1

azure linux advisories AZL-36992

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2020-17049 updated cvss 7.2

Kerberos: delegation constrain bypass in S4U2Proxy

  • Red Hat Enterprise Linux 7 krb5, libkadm5, krb5-libs, krb5-pkinit, krb5-server, krb5-server-ldap, +1 more
    affected: workaround, no fix planned “Will not fix”
  • Red Hat Enterprise Linux AppStream (v. 8) ipa 4.9.12-11.module+el8.9.0+20824+f2605038, pyusb 1.0.0-9.1.module+el8.9.0+18911+94941f82, softhsm 2.6.0-5.module+el8.9.0+18911+94941f82, custodia 0.6.0-3.module+el8.9.0+18911+94941f82, opendnssec 2.1.7-1.module+el8.9.0+18911+94941f82, slapi-nis 0.60.0-4.module+el8.9.0+20420+fef9eb45, +29 more
    fixed: vendor fix RHSA-2024:0143
  • Red Hat Enterprise Linux AppStream (v. 9) krb5-devel 1.20.1-8.el9
    fixed: vendor fix RHSA-2023:2570
  • Red Hat Enterprise Linux AppStream EUS (v.8.6) ipa 4.9.8-11.module+el8.6.0+20984+095e5c46, pyusb 1.0.0-9.module+el8.1.0+4098+f286395e, custodia 0.6.0-3.module+el8.1.0+4098+f286395e, softhsm 2.6.0-5.module+el8.4.0+10227+076cd560, opendnssec 2.1.7-1.module+el8.4.0+9007+5084bdd8, slapi-nis 0.60.0-1.module+el8.6.0+16878+6c033536, +29 more
    fixed: vendor fix RHSA-2024:0139
  • Red Hat Enterprise Linux AppStream EUS (v.8.8) ipa 4.9.11-9.module+el8.8.0+20825+52dd1628, custodia 0.6.0-3.module+el8.1.0+4098+f286395e, pyusb 1.0.0-9.1.module+el8.7.0+15691+2b2c1dd5, softhsm 2.6.0-5.module+el8.4.0+10227+076cd560, opendnssec 2.1.7-1.module+el8.4.0+9007+5084bdd8, slapi-nis 0.60.0-4.module+el8.8.0+20635+330e3683, +29 more
    fixed: vendor fix RHSA-2024:0137
  • Red Hat Enterprise Linux BaseOS (v. 9) krb5 1.20.1-8.el9, libkadm5 1.20.1-8.el9, krb5-libs 1.20.1-8.el9, krb5-pkinit 1.20.1-8.el9, krb5-server 1.20.1-8.el9, krb5-server-ldap 1.20.1-8.el9, +1 more
    fixed: vendor fix RHSA-2023:2570
  • Red Hat Enterprise Linux 7 ctdb, samba, samba-dc, ctdb-tests, samba-libs, samba-pidl, +18 more Red Hat Enterprise Linux 8 ctdb, samba, libnetapi, ctdb-tests, samba-libs, samba-pidl, +24 more Red Hat Enterprise Linux 9 ctdb, samba, libldb, ldb-tools, libnetapi, samba-libs, +27 more Red Hat JBoss Core Services krb5 Red Hat JBoss Enterprise Application Platform 6 krb5 Red Hat Storage 3 ctdb, samba, samba-dc, ctdb-tests, samba-libs, samba-pidl, +21 more
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
total
Assessed
23 mo ago

Exploit prediction

13.79% chance of exploitation in the next 30 days, higher than 96% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 6.6 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
CNA 3.1 6.6 CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H
CNA 3.1 7.2 CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 9.0 AV:N/AC:L/Au:S/C:C/I:C/A:C

Affected products

  • Microsoft Windows Server 2019
  • Microsoft Windows Server 2019 (Server Core installation)
  • Microsoft Windows Server, version 1909 (Server Core installation)
  • Microsoft Windows Server, version 1903 (Server Core installation)
  • Microsoft Windows Server version 2004
  • Microsoft Windows Server 2016
  • Microsoft Windows Server 2016 (Server Core installation)
  • Microsoft Windows Server 2008 Service Pack 2
  • Microsoft Windows Server 2008 Service Pack 2 (Server Core installation)
  • Microsoft Windows Server 2008 Service Pack 2
  • Microsoft Windows Server 2008 R2 Service Pack 1
  • Microsoft Windows Server 2008 R2 Service Pack 1 (Server Core installation)
  • Microsoft Windows Server 2012
  • Microsoft Windows Server 2012 (Server Core installation)
  • Microsoft Windows Server 2012 R2
  • Microsoft Windows Server 2012 R2 (Server Core installation)
  • Microsoft Windows Server version 20H2

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.