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Fencer Vulns
high 7.5

CVE-2020-28196 json

MIT Kerberos 5 (aka krb5) before 1.17.2 and 1.18.x before 1.18.3 allows unbounded recursion via an ASN.1-encoded Kerberos message because t…

published 2020-11-06 6 y ago modified 2026-10-14 25 d ago also EUVD-2020-20680

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
4.2%
EPSS 4.2% chance of exploitation in 30 days, percentile 91%
public exploits
0
none known

Summary

MIT Kerberos 5 (aka krb5) before 1.17.2 and 1.18.x before 1.18.3 allows unbounded recursion via an ASN.1-encoded Kerberos message because the lib/krb5/asn.1/asn1_encode.c support for BER indefinite lengths lacks a recursion limit.

Patch / fix

  • Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP V3.1.5
  • Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP V3.1.5
  • Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP V3.1.5
  • krb5 Debian 14, Debian 13, Debian 12 1.18.3-1

debian advisories DEBIAN-CVE-2020-28196

  • krb5 Ubuntu 16.04 LTS 1.13.2+dfsg-5ubuntu2.2
  • krb5 Ubuntu 18.04 LTS 1.16-2ubuntu0.2
  • krb5 Ubuntu 20.04 LTS 1.17-6ubuntu4.1
  • krb5 Ubuntu Pro 14.04 LTS 1.12+dfsg-2ubuntu5.4+esm2

ubuntu advisories UBUNTU-CVE-2020-28196

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • redhat-virtualization-host rhev hypervisor 4.4 4.4.6-20210527.3.el8_4
  • redhat-virtualization-host-image-update rhev hypervisor 4.4 4.4.6-20210527.3.el8_4
  • krb5 RHEL 8 1.18.2-8.el8
  • libkadm5 RHEL 8 1.18.2-8.el8
  • krb5-libs RHEL 8 1.18.2-8.el8
  • krb5-pkinit RHEL 8 1.18.2-8.el8
  • krb5-server RHEL 8 1.18.2-8.el8
  • krb5-server-ldap RHEL 8 1.18.2-8.el8

red hat advisories RHSA-2021:2239RHSA-2021:1593

  • krb5 SLES for SAP 12 SP5, SLES for SAP 12 SP4, SLES for SAP 12 SP3 +15 more 1.12.5-40.40.2
  • krb5 SLE Module for Server Applications 15 SP2, SLE Module for Server Applications 15 SP1, SLE Module for Basesystem 15 SP2 +1 more 1.16.3-3.15.1
  • krb5 SLES for SAP 15, SLES 15-LTSS, SLE High Performance Computing 15-LTSS +1 more 1.15.2-6.12.2

suse advisories SUSE-SU-2020:3379-1SUSE-SU-2020:3377-1SUSE-SU-2020:3375-1

  • krb5 openSUSE Tumbleweed 1.19.2-3.1
  • krb5 openSUSE Leap 15.2 1.16.3-lp152.5.13.1
  • krb5-mini openSUSE Leap 15.2 1.16.3-lp152.5.13.1
  • krb5 openSUSE Leap 15.1 1.16.3-lp151.2.15.1
  • krb5-mini openSUSE Leap 15.1 1.16.3-lp151.2.15.1

opensuse advisories openSUSE-SU-2024:11549-1openSUSE-SU-2020:2062-1openSUSE-SU-2020:2037-1

  • krb5 Rocky Linux 8 1.18.2-8.el8

rocky linux advisories RLSA-2021:1593

  • krb5 Alpine 3.11, Alpine 3.10 1.17.2-r0
  • krb5 Alpine 3.24, Alpine 3.23, Alpine 3.22 +10 more 1.18.3-r0
  • krb5 Alpine 3.9 1.15.5-r1

alpine advisories ALPINE-CVE-2020-28196

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

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-2020-28196 updated cvss 7.5

krb5: unbounded recursion via an ASN.1-encoded Kerberos message in lib/krb5/asn.1/asn1_encode.c may lead to DoS

  • Red Hat Enterprise Linux 7 krb5, libkadm5, krb5-libs, krb5-pkinit, krb5-server, krb5-server-ldap, +1 more Red Hat JBoss Enterprise Web Server 2 krb5
    affected: no fix planned “Out of support scope”
  • Red Hat Enterprise Linux BaseOS (v. 8) krb5 1.18.2-8.el8, libkadm5 1.18.2-8.el8, krb5-libs 1.18.2-8.el8, krb5-pkinit 1.18.2-8.el8, krb5-server 1.18.2-8.el8, krb5-server-ldap 1.18.2-8.el8, +1 more
    fixed: vendor fix RHSA-2021:1593
  • Red Hat Virtualization 4 Hypervisor for RHEL 8 redhat-virtualization-host 4.4.6-20210527.3.el8_4, redhat-virtualization-host-image-update 4.4.6-20210527.3.el8_4
    fixed: vendor fix RHSA-2021:2239
  • Red Hat Enterprise Linux 5 krb5 Red Hat Enterprise Linux 6 krb5, libkadm5, krb5-libs, krb5-server, krb5-server-ldap, krb5-workstation, +1 more Red Hat JBoss Core Services krb5 Red Hat Virtualization 4 Hypervisor for RHEL 8 elfutils-debuginfod-client 0.182-3.el8 Red Hat Virtualization 4 Management Agent for RHEL 7 Hosts cockpit-ovirt 0.15.0-2.el8ev, ovirt-hosted-engine-ha 2.4.7-1.el8ev, cockpit-ovirt-dashboard 0.15.0-2.el8ev Red Hat RHEL 8-based RHEV-H for RHEV 4 (build requirements) imgbased 1.2.19-1.el8ev, python3-imgbased 1.2.19-1.el8ev, scap-security-guide 0.1.54-1.el8ev, scap-security-guide-rhv 0.1.54-1.el8ev, redhat-release-virtualization-host 4.4.6-1.el8ev, redhat-virtualization-host-image-update-placeholder 4.4.6-1.el8ev
    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 ICSA-23-348-10 updated cvss 7.5

Siemens SIMATIC S7-1500

  • Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0) >= 3.1.0, < 3.1.5 Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0) >= 3.1.0, < 3.1.5 Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0) >= 3.1.0, < 3.1.5 Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0) >= 3.1.0, < 3.1.5 Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0) >= 3.1.0, < 3.1.5
    affected: fixed in V3.1.5, mitigation support.industry.siemens.com

Facts from CISA's republication of the vendor's own advisory (CSAF); the linked advisory is the authoritative source. CISA notification · csaf

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
11 mo ago

Exploit prediction

4.25% chance of exploitation in the next 30 days, higher than 91% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CISA ADP 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD 2.0 5.0 AV:N/AC:L/Au:N/C:N/I:N/A:P

Affected products

  • Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP
  • Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP
  • Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP

Classification

Weakness
Technology feeds

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.