[USN-4976-1] Dnsmasq vulnerability

Marc Deslauriers marc.deslauriers at canonical.com
Wed Jun 2 13:52:49 UTC 2021

Ubuntu Security Notice USN-4976-1
June 02, 2021

dnsmasq vulnerability

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


Dnsmasq could be exposed to cache poisoning.

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


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 21.04:
  dnsmasq                         2.84-1ubuntu2.1
  dnsmasq-base                    2.84-1ubuntu2.1
  dnsmasq-utils                   2.84-1ubuntu2.1

Ubuntu 20.10:
  dnsmasq                         2.82-1ubuntu1.3
  dnsmasq-base                    2.82-1ubuntu1.3
  dnsmasq-utils                   2.82-1ubuntu1.3

Ubuntu 20.04 LTS:
  dnsmasq                         2.80-1.1ubuntu1.4
  dnsmasq-base                    2.80-1.1ubuntu1.4
  dnsmasq-utils                   2.80-1.1ubuntu1.4

Ubuntu 18.04 LTS:
  dnsmasq                         2.79-1ubuntu0.4
  dnsmasq-base                    2.79-1ubuntu0.4
  dnsmasq-utils                   2.79-1ubuntu0.4

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


Package Information:

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