A Kerberos security update has been released for Ubuntu Linux 14.04 ESM, 16.04 LTS, 18.04 LTS, 20.04 LTS, and 20.10.

USN-4635-1: Kerberos vulnerability

=========================================================================
Ubuntu Security Notice USN-4635-1
November 17, 2020

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

- Ubuntu 20.10
- Ubuntu 20.04 LTS
- Ubuntu 18.04 LTS
- Ubuntu 16.04 LTS
- Ubuntu 14.04 ESM

Summary:

Kerberos could be made to consume unlimited resources if it received specially crafted
ASN.1.

Software Description:
- krb5: MIT Kerberos Network Authentication Protocol

Details:

Demi Obenour discovered that Kerberos incorrectly handled certain ASN.1.
An attacker could possibly use this issue to cause a denial of service.

Update instructions:

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

Ubuntu 20.10:
krb5-admin-server 1.17-10ubuntu0.1
krb5-k5tls 1.17-10ubuntu0.1
krb5-kdc 1.17-10ubuntu0.1
krb5-kdc-ldap 1.17-10ubuntu0.1
krb5-kpropd 1.17-10ubuntu0.1
krb5-locales 1.17-10ubuntu0.1
krb5-multidev 1.17-10ubuntu0.1
krb5-otp 1.17-10ubuntu0.1
krb5-pkinit 1.17-10ubuntu0.1
krb5-user 1.17-10ubuntu0.1
libgssapi-krb5-2 1.17-10ubuntu0.1
libgssrpc4 1.17-10ubuntu0.1
libk5crypto3 1.17-10ubuntu0.1
libkadm5clnt-mit11 1.17-10ubuntu0.1
libkadm5srv-mit11 1.17-10ubuntu0.1
libkdb5-9 1.17-10ubuntu0.1
libkrad0 1.17-10ubuntu0.1
libkrb5-3 1.17-10ubuntu0.1
libkrb5support0 1.17-10ubuntu0.1

Ubuntu 20.04 LTS:
krb5-admin-server 1.17-6ubuntu4.1
krb5-k5tls 1.17-6ubuntu4.1
krb5-kdc 1.17-6ubuntu4.1
krb5-kdc-ldap 1.17-6ubuntu4.1
krb5-kpropd 1.17-6ubuntu4.1
krb5-locales 1.17-6ubuntu4.1
krb5-multidev 1.17-6ubuntu4.1
krb5-otp 1.17-6ubuntu4.1
krb5-pkinit 1.17-6ubuntu4.1
krb5-user 1.17-6ubuntu4.1
libgssapi-krb5-2 1.17-6ubuntu4.1
libgssrpc4 1.17-6ubuntu4.1
libk5crypto3 1.17-6ubuntu4.1
libkadm5clnt-mit11 1.17-6ubuntu4.1
libkadm5srv-mit11 1.17-6ubuntu4.1
libkdb5-9 1.17-6ubuntu4.1
libkrad0 1.17-6ubuntu4.1
libkrb5-3 1.17-6ubuntu4.1
libkrb5support0 1.17-6ubuntu4.1

Ubuntu 18.04 LTS:
krb5-admin-server 1.16-2ubuntu0.2
krb5-k5tls 1.16-2ubuntu0.2
krb5-kdc 1.16-2ubuntu0.2
krb5-kdc-ldap 1.16-2ubuntu0.2
krb5-kpropd 1.16-2ubuntu0.2
krb5-locales 1.16-2ubuntu0.2
krb5-otp 1.16-2ubuntu0.2
krb5-pkinit 1.16-2ubuntu0.2
krb5-user 1.16-2ubuntu0.2
libgssapi-krb5-2 1.16-2ubuntu0.2
libgssrpc4 1.16-2ubuntu0.2
libk5crypto3 1.16-2ubuntu0.2
libkadm5clnt-mit11 1.16-2ubuntu0.2
libkadm5srv-mit11 1.16-2ubuntu0.2
libkdb5-9 1.16-2ubuntu0.2
libkrad0 1.16-2ubuntu0.2
libkrb5-3 1.16-2ubuntu0.2
libkrb5support0 1.16-2ubuntu0.2

Ubuntu 16.04 LTS:
krb5-admin-server 1.13.2+dfsg-5ubuntu2.2
krb5-k5tls 1.13.2+dfsg-5ubuntu2.2
krb5-kdc 1.13.2+dfsg-5ubuntu2.2
krb5-kdc-ldap 1.13.2+dfsg-5ubuntu2.2
krb5-locales 1.13.2+dfsg-5ubuntu2.2
krb5-multidev 1.13.2+dfsg-5ubuntu2.2
krb5-otp 1.13.2+dfsg-5ubuntu2.2
krb5-pkinit 1.13.2+dfsg-5ubuntu2.2
krb5-user 1.13.2+dfsg-5ubuntu2.2
libgssapi-krb5-2 1.13.2+dfsg-5ubuntu2.2
libgssrpc4 1.13.2+dfsg-5ubuntu2.2
libk5crypto3 1.13.2+dfsg-5ubuntu2.2
libkadm5clnt-mit9 1.13.2+dfsg-5ubuntu2.2
libkadm5srv-mit9 1.13.2+dfsg-5ubuntu2.2
libkdb5-8 1.13.2+dfsg-5ubuntu2.2
libkrad0 1.13.2+dfsg-5ubuntu2.2
libkrb5-3 1.13.2+dfsg-5ubuntu2.2
libkrb5support0 1.13.2+dfsg-5ubuntu2.2

Ubuntu 14.04 ESM:
krb5-admin-server 1.12+dfsg-2ubuntu5.4+esm2
krb5-kdc 1.12+dfsg-2ubuntu5.4+esm2
krb5-kdc-ldap 1.12+dfsg-2ubuntu5.4+esm2
krb5-locales 1.12+dfsg-2ubuntu5.4+esm2
krb5-multidev 1.12+dfsg-2ubuntu5.4+esm2
krb5-otp 1.12+dfsg-2ubuntu5.4+esm2
krb5-pkinit 1.12+dfsg-2ubuntu5.4+esm2
krb5-user 1.12+dfsg-2ubuntu5.4+esm2
libgssapi-krb5-2 1.12+dfsg-2ubuntu5.4+esm2
libgssrpc4 1.12+dfsg-2ubuntu5.4+esm2
libk5crypto3 1.12+dfsg-2ubuntu5.4+esm2
libkadm5clnt-mit9 1.12+dfsg-2ubuntu5.4+esm2
libkadm5srv-mit8 1.12+dfsg-2ubuntu5.4+esm2
libkadm5srv-mit9 1.12+dfsg-2ubuntu5.4+esm2
libkdb5-7 1.12+dfsg-2ubuntu5.4+esm2
libkrad0 1.12+dfsg-2ubuntu5.4+esm2
libkrb5-3 1.12+dfsg-2ubuntu5.4+esm2
libkrb5support0 1.12+dfsg-2ubuntu5.4+esm2

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

References:
  https://usn.ubuntu.com/4635-1
CVE-2020-28196

Package Information:
  https://launchpad.net/ubuntu/+source/krb5/1.17-10ubuntu0.1
  https://launchpad.net/ubuntu/+source/krb5/1.17-6ubuntu4.1
  https://launchpad.net/ubuntu/+source/krb5/1.16-2ubuntu0.2
  https://launchpad.net/ubuntu/+source/krb5/1.13.2+dfsg-5ubuntu2.2