krb5: Reachable assertion in the KDC using S4U2Self requests
Published Dec 26, 2018
5.3
MEDIUMCVSS 3.1
EPSS 1.42%
Description
A Reachable Assertion issue was discovered in the KDC in MIT Kerberos 5 (aka krb5) before 1.17. If an attacker can obtain a krbtgt ticket using an older encryption type (single-DES, triple-DES, or RC4), the attacker can crash the KDC by making an S4U2Self request.
Affected products
No data.
Configuration 2
- 8.0
- 9.0
No data.
Red Hat Ansible Tower 3.4 for RHEL 7
ansible-tower-34/ansible-tower-memcached:1.4.15-28
Fixed · RHBA-2020:0547
Red Hat Ansible Tower 3.4 for RHEL 7
ansible-tower-35/ansible-tower-memcached:1.4.15-28
Fixed · RHBA-2020:0547
Red Hat Ansible Tower 3.4 for RHEL 7
ansible-tower-37/ansible-tower-memcached-rhel7:1.4.15-28
Fixed · RHBA-2020:0547
Red Hat Enterprise Linux 7
krb5-0:1.15.1-37.el7_7.2
Fixed · RHBA-2019:2599
Red Hat Enterprise Linux 5
krb5
Not affected
Red Hat Enterprise Linux 6
krb5
Will not fix
Red Hat Enterprise Linux 8
krb5
Not affected
Red Hat JBoss Core Services
krb5
Out of support scope
Red Hat JBoss Enterprise Application Platform 6
krb5
Out of support scope
Red Hat JBoss Enterprise Web Server 2
krb5
Out of support scope
| Product | Package | State | Advisory |
|---|---|---|---|
| Red Hat Ansible Tower 3.4 for RHEL 7 | ansible-tower-34/ansible-tower-memcached:1.4.15-28 | Fixed | RHBA-2020:0547 |
| Red Hat Ansible Tower 3.4 for RHEL 7 | ansible-tower-35/ansible-tower-memcached:1.4.15-28 | Fixed | RHBA-2020:0547 |
| Red Hat Ansible Tower 3.4 for RHEL 7 | ansible-tower-37/ansible-tower-memcached-rhel7:1.4.15-28 | Fixed | RHBA-2020:0547 |
| Red Hat Enterprise Linux 7 | krb5-0:1.15.1-37.el7_7.2 | Fixed | RHBA-2019:2599 |
| Red Hat Enterprise Linux 5 | krb5 | Not affected | n/a |
| Red Hat Enterprise Linux 6 | krb5 | Will not fix | n/a |
| Red Hat Enterprise Linux 8 | krb5 | Not affected | n/a |
| Red Hat JBoss Core Services | krb5 | Out of support scope | n/a |
| Red Hat JBoss Enterprise Application Platform 6 | krb5 | Out of support scope | n/a |
| Red Hat JBoss Enterprise Web Server 2 | krb5 | Out of support scope | n/a |
No package ranges for this CVE.
Remediation
No remediation recorded yet.
Metrics
No CVSS v4.0 score for this CVE.
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
CVSS:3.0/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
AV:N/AC:M/Au:S/C:N/I:N/A:P
This CVE is not in the KEV list.
No CISA SSVC assessment for this CVE yet.
Estimated probability of exploitation in the wild in the next 30 days (FIRST EPSS). As of Oct 1, 2026.
Score over time
2021–2026- EPSS v1
- EPSS v5
- EPSS v2
- EPSS v3
- EPSS v4
Percentile over time
- EPSS v1
- EPSS v5
- EPSS v2
- EPSS v3
- EPSS v4
Table of values (18 key points)
Flat stretches are collapsed; showing up to 120 newest points.
| Date | Score | Percentile | Model |
|---|---|---|---|
| Oct 1, 2026 | 1.42% (0.01417) | 71.81th | v5 (v2026.06.15) |
| Jun 15, 2026 | 1.53% (0.01527) | 71.34th | v5 (v2026.06.15) |
| Feb 26, 2026 | 2.67% (0.02665) | 85.54th | v4 (v2025.03.14) |
| Jan 28, 2026 | 4.38% (0.04381) | 88.67th | v4 (v2025.03.14) |
| Nov 18, 2025 | 2.08% (0.02078) | 82.56th | v4 (v2025.03.14) |
| Mar 30, 2025 | 1.05% (0.01052) | 75.57th | v4 (v2025.03.14) |
| Mar 29, 2025 | 7.93% (0.07931) | 86.48th | v4 (v2025.03.14) |
| Mar 17, 2025 | 0.96% (0.00956) | 74.85th | v4 (v2025.03.14) |
| Dec 12, 2024 | 0.24% (0.00240) | 62.87th | v3 (v2023.03.01) |
| Feb 8, 2024 | 0.30% (0.00303) | 68.84th | v3 (v2023.03.01) |
| Dec 20, 2023 | 0.30% (0.00303) | 66.38th | v3 (v2023.03.01) |
| Nov 8, 2023 | 0.24% (0.00235) | 61.37th | v3 (v2023.03.01) |
| Mar 7, 2023 | 0.17% (0.00165) | 51.37th | v3 (v2023.03.01) |
| Mar 6, 2023 | 1.03% (0.01034) | 41.69th | v2 (v2022.01.01) |
| Oct 11, 2021 | 1.45% (0.01454) | 72.27th | v1 |
| Oct 5, 2021 | 6.21% (0.06208) | 89.60th | v1 |
| Oct 4, 2021 | 1.45% (0.01454) | 71.94th | v5 (v2026.06.15) |
| Apr 14, 2021 | 1.25% (0.01247) | 0.00th | v1 |
References (10)
- http://krbdev.mit.edu/rt/Ticket/Display.html?id=8763 x_refsource_CONFIRMPatchThird Party Advisory
- https://access.redhat.com/security/cve/CVE-2018-20217 Vendor Advisory
- https://bugzilla.redhat.com/show_bug.cgi?id=1665296 Issue Tracking
- https://github.com/krb5/krb5/commit/5e6d1796106df8ba6bc1973ee0917c170d929086 x_refsource_CONFIRMPatchThird Party Advisory
- https://lists.debian.org/debian-lts-announce/2019/01/msg00020.html mailing-listx_refsource_MLISTMailing ListThird Party Advisory
- https://lists.debian.org/debian-lts-announce/2021/09/msg00019.html mailing-listx_refsource_MLISTMailing ListThird Party Advisory
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/2KNHELH4YHNT6H2ESJWX2UIDXLBNGB2O/ vendor-advisoryx_refsource_FEDORA
- https://nvd.nist.gov/vuln/detail/CVE-2018-20217
- https://security.netapp.com/advisory/ntap-20190416-0006/ x_refsource_CONFIRMThird Party Advisory
- https://www.cve.org/CVERecord?id=CVE-2018-20217
| Link | Providers | Tags |
|---|---|---|
| http://krbdev.mit.edu/rt/Ticket/Display.html?id=8763 | x_refsource_CONFIRMPatchThird Party Advisory | |
| https://access.redhat.com/security/cve/CVE-2018-20217 | Vendor Advisory | |
| https://bugzilla.redhat.com/show_bug.cgi?id=1665296 | Issue Tracking | |
| https://github.com/krb5/krb5/commit/5e6d1796106df8ba6bc1973ee0917c170d929086 | x_refsource_CONFIRMPatchThird Party Advisory | |
| https://lists.debian.org/debian-lts-announce/2019/01/msg00020.html | mailing-listx_refsource_MLISTMailing ListThird Party Advisory | |
| https://lists.debian.org/debian-lts-announce/2021/09/msg00019.html | mailing-listx_refsource_MLISTMailing ListThird Party Advisory | |
| https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/2KNHELH4YHNT6H2ESJWX2UIDXLBNGB2O/ | vendor-advisoryx_refsource_FEDORA | |
| https://nvd.nist.gov/vuln/detail/CVE-2018-20217 | ||
| https://security.netapp.com/advisory/ntap-20190416-0006/ | x_refsource_CONFIRMThird Party Advisory | |
| https://www.cve.org/CVERecord?id=CVE-2018-20217 |
Change history (0)
No recorded changes yet.