No exploitation reportedFix available

CVE-2026-27858

Q: Is CVE-2026-27858 actively exploited?

Active exploitation of CVE-2026-27858 has not been confirmed. Its EPSS score was 1.0% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

Q: What is the CVSS score for CVE-2026-27858?

CVE-2026-27858 has a CVSS v3 base score of 7.5 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

No exploitation reported by the sources we read.

Published2026-03-27
Fixed in3.1.4 · 3.0.5 · 2.3.22.1
WeaknessCWE-400 · CWE-770

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

Attacker can send a specifically crafted message before authentication that causes managesieve to allocate large amount of memory. Attacker can force managesieve-login to be unavailable by repeatedly crashing the process. Protect access to managesieve protocol, or install fixed version. No publicly available exploits are known.

Timeline

dates in UTC

2026-03-2709:16CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 18:48 UTC

Indicators tagged with this CVE, per day0 indicators over 7 days

Block these indicators

Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2026-27858?format=txt
CSV export: https://api.ismalicious.com/edl/cve/CVE-2026-27858?format=csv
TAXII collection of exploited CVEs
The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD

Open-xchange dovecot

Branch	Affected	Fixed in	Source
3.1	≥ 3.1.0, < 3.1.4	3.1.4	NVD
3.0	≥ 3.0.0, < 3.0.5	3.0.5	NVD
2.3	< 2.3.22.1	2.3.22.1	NVD

Dovecot

Branch	Affected	Fixed in	Source
2.4	< 2.4.3	2.4.3	NVD

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

Update Open-xchange dovecot to 3.1.4 · 3.0.5 · 2.3.22.1

Advisories and patches

documentation.open-xchange.comVendor Advisory

Detection

Nuclei template: none so far
Exploit-DB: no entry
Proof-of-concept repositories: none listed

Sources

NVDCVE recordread 2026-10-23
CISA-ADPSSVC decisionnone2026-03-27
OpenCVESSVC decisionnone—
CNACVSS 3.17.5read 2026-10-23
CNAweakness (CWE)CWE-400, CWE-770read 2026-10-23
FIRST EPSSEPSS score1.0 %2026-10-22

Technical details

CVSS v3 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Published: 2026-03-27
Last Modified: 2026-07-15
NVD status: Modified

Frequently asked questions

What is CVE-2026-27858?

Is CVE-2026-27858 actively exploited?

Active exploitation of CVE-2026-27858 has not been confirmed. Its EPSS score was 1.0% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2026-27858?

CVE-2026-27858 has a CVSS v3 base score of 7.5 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

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