Is CVE-2026-27859 in the CISA KEV catalog?

No. CVE-2026-27859 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2026-27859?

CVE-2026-27859 has a CVSS v3 base score of 5.3 (MEDIUM).

What is the EPSS score for CVE-2026-27859?

CVE-2026-27859 has an EPSS score of 0.37% (29th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2026-27859?

Upgrade dovecot on debian 11 to 1:2.3.13+dfsg1-2+deb11u3 or later. Fixes are available for 3 affected products.

CVE & CISA-KEV Catalog

CVE-2026-27859

MEDIUM

5.3

CVSS v3

NVD

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.

CWE-400Resource Exhaustion

How to fix

Remediation Available

dovecotDebian

Fixed in:1:2.3.13+dfsg1-2+deb11u3CVE-2026-27859

Fixed in:1:2.3.19.1+dfsg1-2.1+deb12u2CVE-2026-27859

Fixed in:1:2.4.1+dfsg1-6+deb13u4CVE-2026-27859

Fixed in:1:2.4.3+dfsg1-1CVE-2026-27859

dovecotUbuntu

Fixed in:1:2.3.16+dfsg1-3ubuntu2.7USN-8136-1

Fixed in:1:2.3.21+dfsg1-2ubuntu6.3USN-8136-1

Fixed in:1:2.4.1+dfsg1-5ubuntu4.1USN-8136-1

dovecot-coreUbuntu

Fixed in:1:2.3.16+dfsg1-3ubuntu2.7USN-8136-1

Fixed in:1:2.3.21+dfsg1-2ubuntu6.3USN-8136-1

Fixed in:1:2.4.1+dfsg1-5ubuntu4.1USN-8136-1

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityNone

IntegrityNone

AvailabilityLow

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Exploit Intelligence

0.37%probability of exploitation in 30 days

29thpercentile

Low risk: more likely to be exploited than 29% of all known CVEs.

References

Vendor Advisory1

documentation.open-xchange.com

Related Vulnerabilities

Other CWE-400 (Resource Exhaustion) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2023-44487	High	7.5	100%	KEV	Fix
CVE-2021-44228	Critical	10.0	100%	KEV + Ransom	Fix
CVE-2011-3192	High	7.8	99%	-	Fix
CVE-2019-11478	Medium	5.3	95%	-	Fix
CVE-2024-25617	Medium	5.3	89%	-	Fix
CVE-2018-1000115	High	7.5	89%	-	Fix

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-04-30.