If auth_username_chars is empty, it is possible to inject arbitrary LDAP filter to Dovecot's LDAP authentication. This leads to potentially bypassing restrictions and allows probing of LDAP structure. Do not clear out auth_username_chars, or install fixed version. No publicly available exploits are known.

The remote openSUSE 16 host has packages installed that are affected by multiple vulnerabilities as referenced in the openSUSE-SU-2026:20554-1 advisory.

    - Update to v2.4.3
    - CVE-2025-59028: Invalid base64 authentication can cause DoS for other logins (bsc#1260894).
    - CVE-2025-59031: decode2text.sh OOXML extraction may follow symlinks and read unintended files during     indexing       (bsc#1260895).
    - CVE-2025-59032: pigeonhole: ManageSieve panic occurs with sieve-connect as a client (bsc#1260902).
    - CVE-2026-24031: SQL injection possible if auth_username_chars is configured empty. Fixed escaping to     always happen.
      v2.4 regression (bsc#1260896).
    - CVE-2026-27855: OTP driver vulnerable to replay attack (bsc#1260900).
    - CVE-2026-27856: Doveadm credentials were not checked using timing-safe checking function (bsc#1260899).
    - CVE-2026-27857: sending excessive parenthesis causes imap-login to use excessive memory (bsc#1260898).
    - CVE-2026-27858: pigeonhole: managesieve-login can allocate large amount of memory during authentication     (bsc#1260901).
    - CVE-2026-27859: excessive RFC 2231 MIME parameters in email would can excessive CPU usage (bsc#1260897).
    - CVE-2026-27860: LDAP query injection possible if auth_username_chars is configured empty. Fixed escaping     to always       happen. v2.4 regression (bsc#1260893).

Tenable has extracted the preceding description block directly from the SUSE 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 SUSE Linux SLES16 / SLES_SAP16 host has packages installed that are affected by multiple vulnerabilities as referenced in the SUSE-SU-2026:21208-1 advisory.

    - Update to v2.4.3
    - CVE-2025-59028: Invalid base64 authentication can cause DoS for other logins (bsc#1260894).
    - CVE-2025-59031: decode2text.sh OOXML extraction may follow symlinks and read unintended files during     indexing       (bsc#1260895).
    - CVE-2025-59032: pigeonhole: ManageSieve panic occurs with sieve-connect as a client (bsc#1260902).
    - CVE-2026-24031: SQL injection possible if auth_username_chars is configured empty. Fixed escaping to     always happen.
      v2.4 regression (bsc#1260896).
    - CVE-2026-27855: OTP driver vulnerable to replay attack (bsc#1260900).
    - CVE-2026-27856: Doveadm credentials were not checked using timing-safe checking function (bsc#1260899).
    - CVE-2026-27857: sending excessive parenthesis causes imap-login to use excessive memory (bsc#1260898).
    - CVE-2026-27858: pigeonhole: managesieve-login can allocate large amount of memory during authentication     (bsc#1260901).
    - CVE-2026-27859: excessive RFC 2231 MIME parameters in email would can excessive CPU usage (bsc#1260897).
    - CVE-2026-27860: LDAP query injection possible if auth_username_chars is configured empty. Fixed escaping     to always       happen. v2.4 regression (bsc#1260893).

Tenable has extracted the preceding description block directly from the SUSE 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 Debian 12 host has packages installed that are affected by multiple vulnerabilities as referenced in the dsa-6197 advisory.

    - -------------------------------------------------------------------------     Debian Security Advisory DSA-6197-1                   security@debian.org     https://www.debian.org/security/                       Moritz Muehlenhoff     April 05, 2026                        https://www.debian.org/security/faq
    - -------------------------------------------------------------------------

    Package        : dovecot     CVE ID         : CVE-2025-59031 CVE-2025-59032 CVE-2026-27855                      CVE-2026-27856 CVE-2026-27857 CVE-2026-27858                      CVE-2026-27859 CVE-2026-59028 CVE-2026-24031                      CVE-2026-27860 CVE-2026-0394

    Multiple vulnerabilities have been discovered in the Dovecot IMAP server     which way result in denial of service, SQL injection, path traversal,     replay attacks or timing side channel attacks.

    For the oldstable distribution (bookworm), these problems have been fixed     in version 1:2.3.19.1+dfsg1-2.1+deb12u2.

    For the stable distribution (trixie), these problems have been fixed in     version 1:2.4.1+dfsg1-6+deb13u4.

    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/

    Mailing list: debian-security-announce@lists.debian.org

Tenable has extracted the preceding description block directly from the Debian 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 22.04 LTS / 24.04 LTS / 25.10 host has packages installed that are affected by multiple vulnerabilities as referenced in the USN-8136-1 advisory.

    It was discovered that Dovecot incorrectly handled invalid base64 SASL data. An attacker could possibly     use this issue to cause a denial of service. This issue only affected Ubuntu 25.10. (CVE-2025-59028)

    It was discovered that Dovecot script decode2text.sh incorrectly handled zip files. An attacker could     possibly use this issue to obtain sensitive information. (CVE-2025-59031)

    It was discovered that Dovecot incorrectly handled certain AUTHENTICATE requests. An attacker could     possibly use this issue to cause a denial of service. (CVE-2025-59032)

    It was discovered that Dovecot incorrectly handled certain SQL based authentication. An attacker could     possibly use this issue to bypass authentication. This issue only affected Ubuntu 25.10. (CVE-2026-24031)

    It was discovered that Dovecot incorrectly handled certain LDAP based authentication. An attacker could     possibly use this issue to bypass restrictions and allow probing of LDAP structure. This issue only     affected Ubuntu 25.10. (CVE-2026-27860)

    It was discovered that Dovecot is vulnerable to replay attack under certain conditions. An attacker could     possibly use this issue to bypass authentication. (CVE-2026-27855)

    It was discovered that Dovecot is vulnerable to a timing attack under certain conditions. An attacker     could possibly use this issue to bypass authentication. (CVE-2026-27856)

    It was discovered that Dovecot incorrectly handled certain IMAP login requests. An attacker could possibly     use this issue to cause a denial of service. (CVE-2026-27857)

    It was discovered that Dovecot incorrectly handled certain specially crafted messages. An attacker could     possibly use this issue to cause a denial of service. (CVE-2026-27858)

    It was discovered that Dovecot incorrectly handled certain specially crafted mail messages. An attacker     could possibly use this issue to cause a denial of service. (CVE-2026-27859)

    It was discovered that Dovecot incorrectly handles file paths. A attacker could possibly use this issue to     perform a path traversal and obtain or modify arbitrary files. This issue only affected Ubuntu 22.04 LTS     and Ubuntu 24.04 LTS. (CVE-2026-0394)

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.

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

  - If auth_username_chars is empty, it is possible to inject arbitrary LDAP filter to Dovecot's LDAP     authentication. This leads to potentially bypassing restrictions and allows probing of LDAP structure. Do     not clear out auth_username_chars, or install fixed version. No publicly available exploits are known.
    (CVE-2026-27860)

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

ID	Name	Product	Family	Severity
309138	openSUSE 16 Security Update : dovecot24 (openSUSE-SU-2026:20554-1)	Nessus	SuSE Local Security Checks	high
309128	SUSE SLES16 Security Update : dovecot24 (SUSE-SU-2026:21208-1)	Nessus	SuSE Local Security Checks	high
305037	Debian dsa-6197 : dovecot-auth-lua - security update	Nessus	Debian Local Security Checks	high
304437	Ubuntu 22.04 LTS / 24.04 LTS / 25.10 : Dovecot vulnerabilities (USN-8136-1)	Nessus	Ubuntu Local Security Checks	high
304092	Linux Distros Unpatched Vulnerability : CVE-2026-27860	Nessus	Misc.	low

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