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

NOTE: Tenable Network Security has extracted the preceding description block directly from the DLA security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.

Aki Tuomi reports :

When imap hibernation is active, an attacker can cause Dovecot to discover file system directory structure and access other users' emails using specially crafted command. The attacker must have valid credentials to access the mail server.

Mail delivery / parsing crashed when the 10 000th MIME part was message/rfc822 (or if parent was multipart/digest). This happened due to earlier MIME parsing changes for CVE-2020-12100.

This update for dovecot23 fixes the following issues :

Security issues fixed :

  - CVE-2020-12100: Fixed a resource exhaustion caused by     deeply nested MIME parts (bsc#1174920).

  - CVE-2020-24386: Fixed an issue with IMAP hibernation     that allowed users to access other users' emails     (bsc#1180405).

  - CVE-2020-25275: Fixed a crash when the 10000th MIME part     was message/rfc822 (bsc#1180406).

Non-security issues fixed :

  - Pigeonhole was updated to version 0.5.11.

  - Dovecot was updated to version 2.3.11.3.

This update was imported from the SUSE:SLE-15-SP1:Update update project.

The remote AlmaLinux 8 host has packages installed that are affected by multiple vulnerabilities as referenced in the ALSA-2021:1887 advisory.

  - An issue was discovered in Dovecot before 2.3.13. By using IMAP IDLE, an authenticated attacker can     trigger unhibernation via attacker-controlled parameters, leading to access to other users' email messages     (and path disclosure). (CVE-2020-24386)

  - Dovecot before 2.3.13 has Improper Input Validation in lda, lmtp, and imap, leading to an application     crash via a crafted email message with certain choices for ten thousand MIME parts. (CVE-2020-25275)

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

The remote Alibaba Cloud Linux 3 host has packages installed that are affected by multiple vulnerabilities as referenced in the ALINUX3-SA-2022:0115 advisory.

    Package updates are available for Alibaba Cloud Linux 3 that fix the following vulnerabilities:

    CVE-2019-11500:
    In Dovecot before 2.2.36.4 and 2.3.x before 2.3.7.2 (and Pigeonhole before 0.5.7.2), protocol processing     can fail for quoted strings. This occurs because '\0' characters are mishandled, and can lead to out-of-     bounds writes and remote code execution.

    CVE-2019-3814:
    It was discovered that Dovecot before versions 2.2.36.1 and 2.3.4.1 incorrectly handled client     certificates. A remote attacker in possession of a valid certificate with an empty username field could     possibly use this issue to impersonate other users.

    CVE-2020-10957:
    In Dovecot before 2.3.10.1, unauthenticated sending of malformed parameters to a NOOP command causes a     NULL Pointer Dereference and crash in submission-login, submission, or lmtp.

    CVE-2020-10958:
    In Dovecot before 2.3.10.1, a crafted SMTP/LMTP message triggers an unauthenticated use-after-free bug in     submission-login, submission, or lmtp, and can lead to a crash under circumstances involving many newlines     after a command.

    CVE-2020-10967:
    In Dovecot before 2.3.10.1, remote unauthenticated attackers can crash the lmtp or submission process by     sending mail with an empty localpart.

    CVE-2020-12100:
    In Dovecot before 2.3.11.3, uncontrolled recursion in submission, lmtp, and lda allows remote attackers to     cause a denial of service (resource consumption) via a crafted e-mail message with deeply nested MIME     parts.

    CVE-2020-12673:
    In Dovecot before 2.3.11.3, sending a specially formatted NTLM request will crash the auth service because     of an out-of-bounds read.

    CVE-2020-12674:
    In Dovecot before 2.3.11.3, sending a specially formatted RPA request will crash the auth service because     a length of zero is mishandled.

    CVE-2020-24386:
    An issue was discovered in Dovecot before 2.3.13. By using IMAP IDLE, an authenticated attacker can     trigger unhibernation via attacker-controlled parameters, leading to access to other users' email messages     (and path disclosure).

    CVE-2020-25275:
    Dovecot before 2.3.13 has Improper Input Validation in lda, lmtp, and imap, leading to an application     crash via a crafted email message with certain choices for ten thousand MIME parts.

Tenable has extracted the preceding description block directly from the Alibaba Cloud Linux security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - Dovecot before 2.3.13 has Improper Input Validation in lda, lmtp, and imap, leading to an application     crash via a crafted email message with certain choices for ten thousand MIME parts. (CVE-2020-25275)

Note that Nessus relies on the presence of the package as reported by the vendor.

According to the versions of the dovecot packages installed, the EulerOS installation on the remote host is affected by the following vulnerabilities :

  - An issue was discovered in Dovecot before 2.3.13. By     using IMAP IDLE, an authenticated attacker can trigger     unhibernation via attacker-controlled parameters,     leading to access to other users' email messages (and     path disclosure).(CVE-2020-24386)

  - Dovecot before 2.3.13 has Improper Input Validation in     lda, lmtp, and imap, leading to an application crash     via a crafted email message with certain choices for     ten thousand MIME parts.(CVE-2020-25275)

Note that Tenable Network Security has extracted the preceding description block directly from the EulerOS security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.

The remote Oracle Linux 8 host has packages installed that are affected by multiple vulnerabilities as referenced in the ELSA-2021-1887 advisory.

    - fix CVE-2020-24386 IMAP hibernation function allows mail access (#1913534)
    - fix CVE-2020-25275 denial of service via mail MIME parsing (#1914019)

Tenable has extracted the preceding description block directly from the Oracle Linux security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote Fedora 32 host has a package installed that is affected by multiple vulnerabilities as referenced in the FEDORA-2021-c90cb486f7 advisory.

  - An issue was discovered in Dovecot before 2.3.13. By using IMAP IDLE, an authenticated attacker can     trigger unhibernation via attacker-controlled parameters, leading to access to other users' email messages     (and path disclosure). (CVE-2020-24386)

  - Dovecot before 2.3.13 has Improper Input Validation in lda, lmtp, and imap, leading to an application     crash via a crafted email message with certain choices for ten thousand MIME parts. (CVE-2020-25275)

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

The Rocky Linux 8.6 host has packages installed that are affected by multiple vulnerabilities as referenced in the CIQ ciqsa-2026_0035 advisory.

    This advisory aggregates security fixes for the dovecot SRPM in CIQ LTS 8.6. It addresses 21 CVEs:
    CVE-2019-11500, CVE-2020-24386, CVE-2020-25275, CVE-2020-12100, CVE-2017-14461, and 16 more.

Tenable has extracted the preceding description block directly from the CIQ security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote Redhat Enterprise Linux 8 host has packages installed that are affected by multiple vulnerabilities as referenced in the RHSA-2021:1887 advisory.

    Dovecot is an IMAP server for Linux and other UNIX-like systems, written primarily with security in mind.
    It also contains a small POP3 server, and supports e-mail in either the maildir or mbox format. The SQL     drivers and authentication plug-ins are provided as subpackages.

    Security Fix(es):

    * dovecot: IMAP hibernation function allows mail access (CVE-2020-24386)

    * dovecot: Denial of service via mail MIME parsing (CVE-2020-25275)

    For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and     other related information, refer to the CVE page(s) listed in the References section.

    Additional Changes:

    For detailed information on changes in this release, see the Red Hat Enterprise Linux 8.4 Release Notes     linked from the References section.

Tenable has extracted the preceding description block directly from the Red Hat Enterprise Linux security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote Ubuntu 16.04 LTS / 18.04 LTS / 20.04 LTS host has packages installed that are affected by multiple vulnerabilities as referenced in the USN-4674-1 advisory.

    It was discovered that Dovecot incorrectly handled certain imap hibernation commands. A remote     authenticated attacker could possibly use this issue to access other users' email. This issue only     affected Ubuntu 18.04 LTS, Ubuntu 20.04 LTS, and Ubuntu 20.10. (CVE-2020-24386)

    Innokentii Sennovskiy discovered that Dovecot incorrectly handled MIME parsing. A remote attacker could     possibly use this issue to cause Dovecot to crash, resulting in a denial of service. (CVE-2020-25275)

Tenable has extracted the preceding description block directly from the Ubuntu security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

This update for dovecot23 fixes the following issues :

Security issues fixed :

CVE-2020-12100: Fixed a resource exhaustion caused by deeply nested MIME parts (bsc#1174920).

CVE-2020-24386: Fixed an issue with IMAP hibernation that allowed users to access other users' emails (bsc#1180405).

CVE-2020-25275: Fixed a crash when the 10000th MIME part was message/rfc822 (bsc#1180406).

Non-security issues fixed :

Pigeonhole was updated to version 0.5.11.

Dovecot was updated to version 2.3.11.3.

Note that Tenable Network Security has extracted the preceding description block directly from the SUSE security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.

ID	名稱	產品	系列	已發布	已更新	嚴重性
144758	Debian DLA-2517-1 : dovecot security update	Nessus	Debian Local Security Checks	2021/1/6	2022/10/14	medium
144841	FreeBSD : mail/dovecot -- multiple vulnerabilities (bd98066d-4ea4-11eb-b412-e86a64caca56)	Nessus	FreeBSD Local Security Checks	2021/1/11	2021/1/13	medium
145396	openSUSE Security Update : dovecot23 (openSUSE-2021-72)	Nessus	SuSE Local Security Checks	2021/1/25	2024/1/26	medium
157483	AlmaLinux 8 : dovecot (ALSA-2021:1887)	Nessus	Alma Linux Local Security Checks	2022/2/9	2022/2/14	medium
236418	Alibaba Cloud Linux 3 : 0115: dovecot (ALINUX3-SA-2022:0115)	Nessus	Alibaba Cloud Linux Local Security Checks	2025/5/14	2025/5/14	critical
229907	Linux Distros Unpatched Vulnerability : CVE-2020-25275	Nessus	Misc.	2025/3/5	2026/11/6	high
145365	openSUSE Security Update : dovecot23 (openSUSE-2021-26)	Nessus	SuSE Local Security Checks	2021/1/25	2024/1/26	medium
145730	EulerOS 2.0 SP8 : dovecot (EulerOS-SA-2021-1139)	Nessus	Huawei Local Security Checks	2021/2/1	2021/2/4	medium
149946	Oracle Linux 8 : dovecot (ELSA-2021-1887)	Nessus	Oracle Linux Local Security Checks	2021/5/26	2024/11/1	medium
145197	Fedora 32 : 1:dovecot (2021-c90cb486f7)	Nessus	Fedora Local Security Checks	2021/1/20	2021/4/12	medium
357898	Rocky Linux 8.6 [CIQ] Security Update: dovecot / dovecot-debuginfo / dovecot-debugsource / dovecot-devel / etc Multiple Vulnerabilities (ciqsa-2026_0035)	Nessus	Rocky Linux Local Security Checks	2026/10/1	2026/10/11	critical
149667	RHEL 8 : dovecot (RHSA-2021:1887)	Nessus	Red Hat Local Security Checks	2021/5/19	2024/11/7	medium
144710	Ubuntu 16.04 LTS / 18.04 LTS / 20.04 LTS : Dovecot vulnerabilities (USN-4674-1)	Nessus	Ubuntu Local Security Checks	2021/1/4	2025/9/3	medium
144757	SUSE SLES15 Security Update : dovecot23 (SUSE-SU-2021:0029-1)	Nessus	SuSE Local Security Checks	2021/1/6	2024/1/30	medium

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