A Dnsmasq regression update has been relased for Ubuntu Linux 16.04 LTS, 18.04 LTS, 20.04 LTS, and 20.10.

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Ubuntu Security Notice USN-4698-2
February 24, 2021

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

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

Summary:

USN-4698-1 introduced regressions in Dnsmasq.

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

Details:

USN-4698-1 fixed vulnerabilities in Dnsmasq. The updates introduced
regressions in certain environments related to issues with multiple
queries, and issues with retries. This update fixes the problem.

Original advisory details:

Moshe Kol and Shlomi Oberman discovered that Dnsmasq incorrectly handled
memory when sorting RRsets. A remote attacker could use this issue to cause
Dnsmasq to hang, resulting in a denial of service, or possibly execute
arbitrary code. (CVE-2020-25681, CVE-2020-25687)
Moshe Kol and Shlomi Oberman discovered that Dnsmasq incorrectly handled
extracting certain names. A remote attacker could use this issue to cause
Dnsmasq to hang, resulting in a denial of service, or possibly execute
arbitrary code. (CVE-2020-25682, CVE-2020-25683)
Moshe Kol and Shlomi Oberman discovered that Dnsmasq incorrectly
implemented address/port checks. A remote attacker could use this issue to
perform a cache poisoning attack. (CVE-2020-25684)
Moshe Kol and Shlomi Oberman discovered that Dnsmasq incorrectly
implemented query resource name checks. A remote attacker could use this
issue to perform a cache poisoning attack. (CVE-2020-25685)
Moshe Kol and Shlomi Oberman discovered that Dnsmasq incorrectly handled
multiple query requests for the same resource name. A remote attacker could
use this issue to perform a cache poisoning attack. (CVE-2020-25686)
It was discovered that Dnsmasq incorrectly handled memory during DHCP
response creation. A remote attacker could possibly use this issue to
cause Dnsmasq to consume resources, leading to a denial of service. This
issue only affected Ubuntu 16.04 LTS, Ubuntu 18.04 LTS, and Ubuntu 20.04
LTS. (CVE-2019-14834)

Update instructions:

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

Ubuntu 20.10:
dnsmasq 2.82-1ubuntu1.2
dnsmasq-base 2.82-1ubuntu1.2
dnsmasq-utils 2.82-1ubuntu1.2

Ubuntu 20.04 LTS:
dnsmasq 2.80-1.1ubuntu1.3
dnsmasq-base 2.80-1.1ubuntu1.3
dnsmasq-utils 2.80-1.1ubuntu1.3

Ubuntu 18.04 LTS:
dnsmasq 2.79-1ubuntu0.3
dnsmasq-base 2.79-1ubuntu0.3
dnsmasq-utils 2.79-1ubuntu0.3

Ubuntu 16.04 LTS:
dnsmasq 2.75-1ubuntu0.16.04.8
dnsmasq-base 2.75-1ubuntu0.16.04.8
dnsmasq-utils 2.75-1ubuntu0.16.04.8

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

References:
  https://usn.ubuntu.com/4698-2
  https://usn.ubuntu.com/4698-1
  https://launchpad.net/bugs/1916462

Package Information:
  https://launchpad.net/ubuntu/+source/dnsmasq/2.82-1ubuntu1.2
  https://launchpad.net/ubuntu/+source/dnsmasq/2.80-1.1ubuntu1.3
  https://launchpad.net/ubuntu/+source/dnsmasq/2.79-1ubuntu0.3
  https://launchpad.net/ubuntu/+source/dnsmasq/2.75-1ubuntu0.16.04.8