What is CVE-2026-27859?

CVE-2026-27859 is a medium-severity vulnerability in Dovecot, classified under Uncontrolled Resource Consumption. CVSS score: 5.3/10. Published 2026-03-27.

How severe is CVE-2026-27859?

Medium severity. CVSS v3 base score is 5.3 out of 10.

Resource exhaustion in Dovecot

CVE-2026-27859

A mail message containing excessive amount of RFC 2231 MIME parameters causes LMTP to use too much CPU. A suitably formatted mail message causes mail delivery process to consume large amounts of CPU time. Use MTA capabilities to limit RFC 2231 MIME parameters in mail messages, or upgrade to fixed version where the processing is limited. No publicly available exploits are known.

Vulnerability class: DoS (Denial of Service)

EPSS: 0.004 (30.5th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L.

Affected products

Dovecot
Open-xchange Dovecot
Open-xchange Gmbh Ox Dovecot Pro — versions 0

Weakness classification (CWE)

CWE-400 — Uncontrolled Resource Consumption

References

security@open-xchange.com (vendor-advisory, Vendor Advisory)

Frequently asked questions

What is CVE-2026-27859?: CVE-2026-27859 is a medium-severity vulnerability in Dovecot, classified under Uncontrolled Resource Consumption. CVSS score: 5.3/10. Published 2026-03-27.
How severe is CVE-2026-27859?: Medium severity. CVSS v3 base score is 5.3 out of 10.