A Bind security update has been released for Ubuntu Linux 18.04 LTS, 20.04 LTS, 21.04, and 21.10.

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Ubuntu Security Notice USN-5126-1
October 28, 2021

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

- Ubuntu 21.10
- Ubuntu 21.04
- Ubuntu 20.04 LTS
- Ubuntu 18.04 LTS

Summary:

Bind could be made to consume resources if it received specially crafted
network traffic.

Software Description:
- bind9: Internet Domain Name Server

Details:

Kishore Kumar Kothapalli discovered that Bind incorrectly handled the lame
cache when processing responses. A remote attacker could possibly use this
issue to cause Bind to consume resources, resulting in a denial of service.

Update instructions:

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

Ubuntu 21.10:
bind9 1:9.16.15-1ubuntu1.1

Ubuntu 21.04:
bind9 1:9.16.8-1ubuntu3.2

Ubuntu 20.04 LTS:
bind9 1:9.16.1-0ubuntu2.9

Ubuntu 18.04 LTS:
bind9 1:9.11.3+dfsg-1ubuntu1.16

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

References:
  https://ubuntu.com/security/notices/USN-5126-1
CVE-2021-25219

Package Information:
  https://launchpad.net/ubuntu/+source/bind9/1:9.16.15-1ubuntu1.1
  https://launchpad.net/ubuntu/+source/bind9/1:9.16.8-1ubuntu3.2
  https://launchpad.net/ubuntu/+source/bind9/1:9.16.1-0ubuntu2.9
  https://launchpad.net/ubuntu/+source/bind9/1:9.11.3+dfsg-1ubuntu1.16