IMAP Server Denial of Service Vulnerability in Dovecot by Open-Xchange
CVE-2026-40014

6.5MEDIUM

Key Information:

Vendor

Open-xchange Gmbh

Status
Ox Dovecot Pro
Ox Dovecot Ce
Vendor
CVE Published:
28 August 2026

What is CVE-2026-40014?

An attacker with mail-sending capabilities can manipulate message headers to exploit the IMAP THREAD command, leading to excessive CPU consumption during the processing of mailboxes. This can result in performance degradation or denial of service for users accessing the mailbox via IMAP. System administrators are advised to monitor CPU activity for abnormalities, terminate the process if needed, and remove any malicious messages. Users should ensure they are running a patched version of Dovecot to mitigate the risks associated with this vulnerability.

Affected Version(s)

OX Dovecot CE 2.3.0 < 2.4.5

OX Dovecot Pro 2.3.0 < 2.3.22.2

OX Dovecot Pro 3.0.0 < 3.0.7

References

https://documentation.open-xchange.com/dovecot/security/a...
vendor-advisory

CVSS V3.1

Score:
6.5
Severity:
MEDIUM
Confidentiality:
None
Integrity:
None
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
Required
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

.