A Dnsmasq security update has been released for Ubuntu Linux 16.04 ESM.

USN-4976-2: Dnsmasq vulnerability

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Ubuntu Security Notice USN-4976-2
September 07, 2022

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

- Ubuntu 16.04 ESM

Summary:

Dnsmasq could be exposed to cache poisoning.

Software Description:
- dnsmasq: Small caching DNS proxy and DHCP/TFTP server

Details:

USN-4976-1 fixed a vulnerability in Dnsmasq. This update provides
the corresponding update for Ubuntu 16.04 ESM.

Dnsmasq has been updated to 2.79-1 for Ubuntu 16.04 ESM in order to fix
some security issues.

Original advisory details:

Petr Mensik discovered that Dnsmasq incorrectly randomized source ports in
certain configurations. A remote attacker could possibly use this issue to
facilitate DNS cache poisoning attacks.

Update instructions:

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

Ubuntu 16.04 ESM:
dnsmasq 2.79-1ubuntu0.16.04.1+esm1
dnsmasq-base 2.79-1ubuntu0.16.04.1+esm1
dnsmasq-utils 2.79-1ubuntu0.16.04.1+esm1

After a standard system update you need to reboot your computer to make
all the necessary changes.

References:
  https://ubuntu.com/security/notices/USN-4976-2
  https://ubuntu.com/security/notices/USN-4976-1
CVE-2021-3448