An unbound security update has been released for Ubuntu Linux 18.04 LTS and 20.04 LTS.

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Ubuntu Security Notice USN-4938-1
May 06, 2021

unbound vulnerabilities
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A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 20.04 LTS
- Ubuntu 18.04 LTS

Summary:

Several security issues were fixed in Unbound.

Software Description:
- unbound: validating, recursive, caching DNS resolver

Details:

It was discovered that Unbound contained multiple security issues. A
remote attacker could possibly use these issues to cause a denial of
service, inject arbitrary commands, execute arbitrary code, and overwrite
local files.

Update instructions:

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

Ubuntu 20.04 LTS:
libunbound8 1.9.4-2ubuntu1.2
unbound 1.9.4-2ubuntu1.2

Ubuntu 18.04 LTS:
libunbound2 1.6.7-1ubuntu2.4
unbound 1.6.7-1ubuntu2.4

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

References:
  https://ubuntu.com/security/notices/USN-4938-1
CVE-2019-25031, CVE-2019-25032, CVE-2019-25033, CVE-2019-25034,
CVE-2019-25035, CVE-2019-25036, CVE-2019-25037, CVE-2019-25038,
CVE-2019-25039, CVE-2019-25040, CVE-2019-25041, CVE-2019-25042,
CVE-2020-28935

Package Information:
  https://launchpad.net/ubuntu/+source/unbound/1.9.4-2ubuntu1.2
  https://launchpad.net/ubuntu/+source/unbound/1.6.7-1ubuntu2.4