How severe is CVE-2026-27859?

CVE-2026-27859 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability low.

Is CVE-2026-27859 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (29th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-27859?

CVE-2026-27859 primarily affects Open-xchange Dovecot. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2026-27859?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2026-27859 have an EU (EUVD) identifier?

Yes. CVE-2026-27859 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-16571.

When was CVE-2026-27859 published?

CVE-2026-27859 was published on 2026-03-27 and last updated on 2026-06-17.

CVE-2026-27859

CVE-2026-27859 is a medium-severity vulnerability in Open-xchange Dovecot with a CVSS 3.x base score of 5.3. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-400.

Key facts

Severity: Medium (CVSS 3.x base score 5.3)
EPSS exploit prediction: 0% (29th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-16571
Weakness: CWE-400
Affected product: Open-xchange Dovecot
Published: 2026-03-27
Last modified: 2026-06-17

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.

Frequently asked questions

What is 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.
How severe is CVE-2026-27859?: CVE-2026-27859 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability low.
Is CVE-2026-27859 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (29th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-27859?: CVE-2026-27859 primarily affects Open-xchange Dovecot. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2026-27859?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-27859 have an EU (EUVD) identifier?: Yes. CVE-2026-27859 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-16571.
When was CVE-2026-27859 published?: CVE-2026-27859 was published on 2026-03-27 and last updated on 2026-06-17.

References

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

Affected products (2)

cpe:2.3:a:dovecot:dovecot:*:*:*:*:*:*:*:*
cpe:2.3:a:open-xchange:dovecot:*:*:*:*:pro:*:*:*

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