What is CVE-2026-27858?

CVE-2026-27858 is a high-severity vulnerability in Dovecot, classified under Uncontrolled Resource Consumption. CVSS score: 7.5/10. Published 2026-03-27.

How severe is CVE-2026-27858?

High severity. CVSS v3 base score is 7.5 out of 10.

Resource exhaustion in Dovecot

CVE-2026-27858

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…

Vulnerability class: DoS (Denial of Service)

EPSS: 0.000 (15.2th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

Affected products

Dovecot
Open-xchange Dovecot
Open-xchange Gmbh Ox Dovecot Pro — versions 0

Weakness classification (CWE)

CWE-400 — Uncontrolled Resource Consumption

References

security@open-xchange.com (vendor-advisory, Vendor Advisory)

Frequently asked questions

What is CVE-2026-27858?: CVE-2026-27858 is a high-severity vulnerability in Dovecot, classified under Uncontrolled Resource Consumption. CVSS score: 7.5/10. Published 2026-03-27.
How severe is CVE-2026-27858?: High severity. CVSS v3 base score is 7.5 out of 10.