What is CVE-2026-40016?

CVE-2026-40016 is a medium-severity vulnerability in Dovecot, classified under Uncontrolled Resource Consumption. CVSS score: 5.3/10. Published 2026-05-12.

How severe is CVE-2026-40016?

Medium severity. CVSS v3 base score is 5.3 out of 10.

Resource exhaustion in Dovecot

CVE-2026-40016

Attacker can upload a malicious Sieve script over ManageSieve service (or locally) to bypass configured CPU time limits for Sieve up to 130 times of the configured limit. Attacker can use this to degrade server performance and bypass confi…

Vulnerability class: DoS (Denial of Service)

EPSS: 0.000 (3.6th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:L/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-2026-40016?: CVE-2026-40016 is a medium-severity vulnerability in Dovecot, classified under Uncontrolled Resource Consumption. CVSS score: 5.3/10. Published 2026-05-12.
How severe is CVE-2026-40016?: Medium severity. CVSS v3 base score is 5.3 out of 10.