A dovecot security update has been released for Debian GNU/Linux 9 LTS to address two security issues.

DLA 2517-1: dovecot security update

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Debian LTS Advisory DLA-2517-1 debian-lts@lists.debian.org
  https://www.debian.org/lts/security/ Chris Lamb
January 05, 2021   https://wiki.debian.org/LTS
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Package : dovecot
Version : 1:2.2.27-3+deb9u7
CVE IDs : CVE-2020-24386 & CVE-2020-25275

It was discovered that there were two issues in the Dovecot IMAP
server:

* CVE-2020-24386: Prevent an issue where an attacker could cause
Dovecot to discover file system directory structure and even
access other users' emails using a pecially crafted command.

* CVE-2020-25275: Prevent an issue where a malicious sender can
crash Dovecot repeatedly by sending messages with more than
10,000 MIME parts.

For Debian 9 "Stretch", these problems has been fixed in version
1:2.2.27-3+deb9u7 and we recommend that you upgrade your dovecot
packages.

For the detailed security status of dovecot please refer to
its security tracker page at:
  https://security-tracker.debian.org/tracker/dovecot

Further information about Debian LTS security advisories, how to apply
these updates to your system and frequently asked questions can be
found at:   https://wiki.debian.org/LTS