Medium severity · published Mar 27, 2026
CVE-2026-27859
A mail message containing excessive amount of RFC 2231 MIME parameters causes LMTP to use too much CPU
5.3
CVSS
0.4%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
None
Availability
Low
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.4% · higher than 32% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
OD
OX Dovecot Pro · Open-Xchange GmbH
through 3.0.2; through 3.1.0; through 2.4.0 · source: vendor
DO
Dovecot · Dovecot
before 2.4.3 · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-27859
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-27859
Vendor Advisory
https://documentation.open-xchange.com/dovecot/security/advisories/csaf/2026/oxdc-adv-2026-0001.json
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