=========================================================================Ubuntu Security Notice USN-4929-1
April 29, 2021

bind9 vulnerabilities
=========================================================================
A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 21.04
- Ubuntu 20.10
- Ubuntu 20.04 LTS
- Ubuntu 18.04 LTS
- Ubuntu 16.04 LTS

Summary:

Several security issues were fixed in Bind.

Software Description:
- bind9: Internet Domain Name Server

Details:

Greg Kuechle discovered that Bind incorrectly handled certain incremental
zone updates. A remote attacker could possibly use this issue to cause Bind
to crash, resulting in a denial of service. (CVE-2021-25214)

Siva Kakarla discovered that Bind incorrectly handled certain DNAME
records. A remote attacker could possibly use this issue to cause Bind to
crash, resulting in a denial of service. (CVE-2021-25215)

It was discovered that Bind incorrectly handled GSSAPI security policy
negotiation. A remote attacker could use this issue to cause Bind to crash,
resulting in a denial of service, or possibly execute arbitrary code.
(CVE-2021-25216)

Update instructions:

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

Ubuntu 21.04:
  bind9                           1:9.16.8-1ubuntu3.1

Ubuntu 20.10:
  bind9                           1:9.16.6-3ubuntu1.2

Ubuntu 20.04 LTS:
  bind9                           1:9.16.1-0ubuntu2.8

Ubuntu 18.04 LTS:
  bind9                           1:9.11.3+dfsg-1ubuntu1.15

Ubuntu 16.04 LTS:
  bind9                           1:9.10.3.dfsg.P4-8ubuntu1.19

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

References:
  https://ubuntu.com/security/notices/USN-4929-1
  CVE-2021-25214, CVE-2021-25215, CVE-2021-25216

Package Information:
  https://launchpad.net/ubuntu/+source/bind9/1:9.16.8-1ubuntu3.1
  https://launchpad.net/ubuntu/+source/bind9/1:9.16.6-3ubuntu1.2
  https://launchpad.net/ubuntu/+source/bind9/1:9.16.1-0ubuntu2.8
  https://launchpad.net/ubuntu/+source/bind9/1:9.11.3+dfsg-1ubuntu1.15
  https://launchpad.net/ubuntu/+source/bind9/1:9.10.3.dfsg.P4-8ubuntu1.19