A dovecot security update has been released for Debian GNU/Linux 10 to address several vulnerabilities.

DSA 4825-1: dovecot security update

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Debian Security Advisory DSA-4825-1 security@debian.org
  https://www.debian.org/security/ Salvatore Bonaccorso
January 04, 2021   https://www.debian.org/security/faq
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Package : dovecot
CVE ID : CVE-2020-24386 CVE-2020-25275

Several vulnerabilities have been discovered in the Dovecot email
server.

CVE-2020-24386

When imap hibernation is active, an attacker (with valid credentials
to access the mail server) can cause Dovecot to discover file system
directory structures and access other users' emails via specially
crafted commands.

CVE-2020-25275

Innokentii Sennovskiy reported that the mail delivery and parsing in
Dovecot can crash when the 10000th MIME part is message/rfc822 (or
if the parent was multipart/digest). This flaw was introduced by
earlier changes addressing CVE-2020-12100.

For the stable distribution (buster), these problems have been fixed in
version 1:2.3.4.1-5+deb10u5.

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 Security Advisories, how to apply
these updates to your system and frequently asked questions can be
found at:   https://www.debian.org/security/