A Kerberos security update has been released for Ubuntu Linux 18.04 LTS and 20.04 LTS.

USN-5959-1: Kerberos vulnerabilities

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Ubuntu Security Notice USN-5959-1
March 16, 2023

krb5 vulnerabilities
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A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 20.04 LTS
- Ubuntu 18.04 LTS

Summary:

Several security issues were fixed in Kerberos.

Software Description:
- krb5: MIT Kerberos Network Authentication Protocol

Details:

It was discovered that Kerberos incorrectly handled memory when processing
KDC data, which could lead to a NULL pointer dereference. An attacker could
possibly use this issue to cause a denial of service or have other
unspecified impacts. (CVE-2021-36222, CVE-2021-37750)

Update instructions:

The problem can be corrected by updating your system to the following
package versions:

Ubuntu 20.04 LTS:
krb5-k5tls 1.17-6ubuntu4.3
krb5-kdc 1.17-6ubuntu4.3
krb5-kdc-ldap 1.17-6ubuntu4.3
krb5-pkinit 1.17-6ubuntu4.3

Ubuntu 18.04 LTS:
krb5-k5tls 1.16-2ubuntu0.4
krb5-kdc 1.16-2ubuntu0.4
krb5-kdc-ldap 1.16-2ubuntu0.4
krb5-pkinit 1.16-2ubuntu0.4

In general, a standard system update will make all the necessary changes.

References:
  https://ubuntu.com/security/notices/USN-5959-1
CVE-2021-36222, CVE-2021-37750

Package Information:
  https://launchpad.net/ubuntu/+source/krb5/1.17-6ubuntu4.3
  https://launchpad.net/ubuntu/+source/krb5/1.16-2ubuntu0.4