=========================================================================
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