Excessive RFC2231 MIME Parameters cause LMTP CPU exhaustion in Postfix
CVE-2026-27859 Published on March 27, 2026
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 Analysis
CVE-2026-27859 can be exploited with network access, and does not require authorization privileges or user interaction. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have no impact on confidentiality and integrity, and a small impact on availability.
Weakness Type
What is a Resource Exhaustion Vulnerability?
The software does not properly control the allocation and maintenance of a limited resource, thereby enabling an actor to influence the amount of resources consumed, eventually leading to the exhaustion of available resources.
CVE-2026-27859 has been classified to as a Resource Exhaustion vulnerability or weakness.
Products Associated with CVE-2026-27859
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Affected Versions
Open-Xchange GmbH OX Dovecot Pro:- Before and including 3.0.2 is affected.
- Before and including 3.1.0 is affected.
- Before and including 2.4.0 is affected.
Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.