A Bind security update has been released for Ubuntu 14.04 ESM and 16.04 ESM.

USN-5332-2: Bind vulnerability

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Ubuntu Security Notice USN-5332-2
March 17, 2022

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

- Ubuntu 16.04 ESM
- Ubuntu 14.04 ESM

Summary:

Bind could be made to manipulate cache results.

Software Description:
- bind9: Internet Domain Name Server

Details:

USN-5332-1 fixed a vulnerability in Bind. This update provides
the corresponding update for Ubuntu 14.04 ESM and Ubuntu 16.04 ESM.

Original advisory details:

Xiang Li, Baojun Liu, Chaoyi Lu, and Changgen Zou discovered that Bind
incorrectly handled certain bogus NS records when using forwarders. A
remote attacker could possibly use this issue to manipulate cache results.
(CVE-2021-25220)

Update instructions:

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

Ubuntu 16.04 ESM:
bind9 1:9.10.3.dfsg.P4-8ubuntu1.19+esm2

Ubuntu 14.04 ESM:
bind9 1:9.9.5.dfsg-3ubuntu0.19+esm6

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

References:
  https://ubuntu.com/security/notices/USN-5332-2
  https://ubuntu.com/security/notices/USN-5332-1
CVE-2021-25220