CVE-2026-27859

Severity: medium (CVSS 5.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-03-27 · updated 2026-10-26
Weakness: CWE-400

Description

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.

Affected products

dovecot: before 2.4.3 — fixed in 2.4.3
Open-Xchange Dovecot: before 3.0.5; from 3.1.0 before 3.1.4 — fixed in 3.0.5, 3.1.4

How to fix

Upgrade to a fixed version: dovecot 2.4.3; Open-Xchange Dovecot 3.0.5, 3.1.4. Check the vendor advisory for mitigations.

References

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

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