When sending invalid base64 SASL data, login process is disconnected from the auth server, causing all active authentication sessions to fail. Invalid BASE64 data can be used to DoS a vulnerable server to break concurrent logins. Install fixed version or disable concurrency in login processes (heavy perfomance penalty on large deployments). 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 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.

  - When sending invalid base64 SASL data, login process is disconnected from the auth server, causing all     active authentication sessions to fail. Invalid BASE64 data can be used to DoS a vulnerable server to     break concurrent logins. Install fixed version or disable concurrency in login processes (heavy perfomance     penalty on large deployments). No publicly available exploits are known. (CVE-2025-59028)

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
304437	Ubuntu 22.04 LTS / 24.04 LTS / 25.10 : Dovecot vulnerabilities (USN-8136-1)	Nessus	Ubuntu Local Security Checks	high
304143	Linux Distros Unpatched Vulnerability : CVE-2025-59028	Nessus	Misc.	medium

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CVE-2025-59028

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Tenable Plugins

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