A Dovecot security update has been released for Ubuntu Linux 20.04 LTS, 18.04 LTS, and 16.04 LTS.

USN-4456-1: Dovecot vulnerabilities

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Ubuntu Security Notice USN-4456-1
August 12, 2020

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

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

Summary:

Several security issues were fixed in Dovecot.

Software Description:
- dovecot: IMAP and POP3 email server

Details:

It was discovered that Dovecot incorrectly handled deeply nested MIME
parts. A remote attacker could possibly use this issue to cause Dovecot to
consume resources, resulting in a denial of service. (CVE-2020-12100)

It was discovered that Dovecot incorrectly handled memory when using NTLM.
A remote attacker could possibly use this issue to cause Dovecot to crash,
resulting in a denial of service. (CVE-2020-12673)

It was discovered that the Dovecot RPA mechanism incorrectly handled
zero-length messages. A remote attacker could possibly use this issue to
cause Dovecot to crash, resulting in a denial of service. (CVE-2020-12674)

Update instructions:

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

Ubuntu 20.04 LTS:
dovecot-core 1:2.3.7.2-1ubuntu3.2

Ubuntu 18.04 LTS:
dovecot-core 1:2.2.33.2-1ubuntu4.6

Ubuntu 16.04 LTS:
dovecot-core 1:2.2.22-1ubuntu2.13

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

References:
  https://usn.ubuntu.com/4456-1
CVE-2020-12100, CVE-2020-12673, CVE-2020-12674

Package Information:
  https://launchpad.net/ubuntu/+source/dovecot/1:2.3.7.2-1ubuntu3.2
  https://launchpad.net/ubuntu/+source/dovecot/1:2.2.33.2-1ubuntu4.6
  https://launchpad.net/ubuntu/+source/dovecot/1:2.2.22-1ubuntu2.13