CVE-2018-20217

Publication date 26 December 2018

Last updated 25 August 2025

Ubuntu priority

Medium

Why this priority?

Cvss 3 Severity Score

5.3 · Medium

Score breakdown

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.

From the Ubuntu Security Team

It was discovered that Kerberos incorrectly handled certain S4U2Self requests. An attacker could possibly use this issue to cause a denial of service.

Status

Package Ubuntu Release Status
krb5 22.10 kinetic
Not affected
22.04 LTS jammy
Not affected
21.10 impish
Not affected
21.04 hirsute
Not affected
20.10 groovy
Not affected
20.04 LTS focal
Not affected
19.10 eoan Ignored end of life
19.04 disco Ignored end of life
18.10 cosmic Ignored end of life
18.04 LTS bionic
Fixed 1.16-2ubuntu0.3
16.04 LTS xenial
Fixed 1.13.2+dfsg-5ubuntu2.2+esm3
14.04 LTS trusty
Fixed 1.12+dfsg-2ubuntu5.4+esm1

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Patch details

For informational purposes only. We recommend not to cherry-pick updates. How can I get the fixes?

Package Patch details
krb5

Severity score breakdown

CVSS version: CVSS v3.0

Base score 5.3 · Medium

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

References

Related Ubuntu Security Notices (USN)

    • USN-5828-1
    • Kerberos vulnerabilities
    • 25 January 2023

Other references

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