Excessive RFC 2231 MIME Parameters Cause Performance Issues in Dovecot Mail Server
CVE-2026-27859

5.3MEDIUM

Key Information:

Vendor

Open-xchange Gmbh

Status
Ox Dovecot Pro
Vendor
CVE Published:
27 March 2026

What is CVE-2026-27859?

A vulnerability exists in the Dovecot Mail Server where a crafted mail message with an excessive number of RFC 2231 MIME parameters can lead to high CPU usage during the mail delivery process. This can significantly impair server performance and affect mail delivery efficiency. Administrators are advised to employ MTA capabilities to restrict the number of RFC 2231 MIME parameters in incoming mail messages or to upgrade to a newer version of Dovecot where this processing limitation is enforced. Currently, there are no known public exploits for this issue.

Affected Version(s)

OX Dovecot Pro 0 <= 3.0.2

OX Dovecot Pro 0 <= 3.1.0

OX Dovecot Pro 0 <= 2.4.0

References

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

CVSS V3.1

Score:
5.3
Severity:
MEDIUM
Confidentiality:
None
Integrity:
None
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

.