Resource exhaustion in Dovecot and OX Dovecot Pro - CVE-2026-27859

Vulnerability identifier: #VU124727

CSH Severity: Medium

CVSS v4: 6.9 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:L]

CVE-ID: CVE-2026-27859

CWE-ID: CWE-400

Exploitation vector: Remote access

Exploit availability: No public exploit available

The vulnerability allows a remote attacker to cause a denial of service.

The vulnerability exists due to uncontrolled resource consumption in MIME parameter parsing when processing message headers. A remote attacker can send a specially crafted email message with excessive RFC 2231 MIME parameters to cause a denial of service of the LMTP mail delivery process.

Dovecot
OX Dovecot Pro
SUSE Linux Enterprise Server 12 SP5
SUSE Linux Enterprise Server 12 SP5 LTSS Extended
SUSE Linux Enterprise High Performance Computing 12
SUSE Linux Enterprise Server 12
SUSE Linux Enterprise Server for SAP Applications 12
openEuler
Ubuntu
dovecot22-backend-pgsql-debuginfo
dovecot22-backend-sqlite
dovecot22-devel
dovecot22
dovecot22-debuginfo
dovecot22-backend-pgsql
dovecot22-backend-mysql-debuginfo
dovecot22-backend-sqlite-debuginfo
dovecot22-debugsource
dovecot22-backend-mysql
dovecot-help
dovecot-devel
dovecot-debugsource
dovecot-debuginfo
dovecot
dovecot (Ubuntu package)

Install security update from vendor's website.

Dovecot - update to 2.4.3
OX Dovecot Pro - addressed in versions 3.0.5, 3.1.4
dovecot22-backend-pgsql-debuginfo - update to 2.2.31-19.32.1
dovecot22-backend-sqlite - update to 2.2.31-19.32.1
dovecot22-devel - update to 2.2.31-19.32.1
dovecot22 - update to 2.2.31-19.32.1
dovecot22-debuginfo - update to 2.2.31-19.32.1
dovecot22-backend-pgsql - update to 2.2.31-19.32.1
dovecot22-backend-mysql-debuginfo - update to 2.2.31-19.32.1
dovecot22-backend-sqlite-debuginfo - update to 2.2.31-19.32.1
dovecot22-debugsource - update to 2.2.31-19.32.1
dovecot22-backend-mysql - update to 2.2.31-19.32.1
dovecot-help - update to 2.3.15-7
dovecot-devel - update to 2.3.15-7
dovecot-debugsource - update to 2.3.15-7
dovecot-debuginfo - update to 2.3.15-7
dovecot - update to 2.3.15-7
dovecot (Ubuntu package) - addressed in versions 1:2.3.16+dfsg1-3ubuntu2.7, 1:2.3.16+dfsg1-3ubuntu2.8, 1:2.3.21+dfsg1-2ubuntu6.3, 1:2.3.21+dfsg1-2ubuntu6.4, 1:2.4.1+dfsg1-5ubuntu4.1

• https://documentation.open-xchange.com/dovecot/security/advisories/html/2026/oxdc-adv-2026-0001.html

• Multiple vulnerabilities in Dovecot
• Ubuntu update for dovecot
• openEuler update for dovecot
• SUSE update for dovecot22
• Ubuntu update for dovecot