Is CVE-2026-40020 in the CISA KEV catalog?

No. CVE-2026-40020 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2026-40020?

CVE-2026-40020 has a CVSS v3 base score of 3.1 (LOW).

What is the EPSS score for CVE-2026-40020?

CVE-2026-40020 has an EPSS score of 0.27% (19th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2026-40020?

Upgrade dovecot on debian 11 to 1:2.3.13+dfsg1-2+deb11u4 or later. Fixes are available for 3 affected products.

CVE & CISA-KEV Catalog

CVE-2026-40020

LOW

3.1

CVSS v3

NVD

Description

Attacker can use the IMAP SETACL command to inject the anyone permission to user's dovecot-acl file even if imap_acl_allow_anyone=no. This causes folders to be spammed to all users. The impact is limited to being able to spam folders to other users, no unexpected access is gained. Install to fixed version. No publicly available exploits are known.

CWE-284Improper Access Control

How to fix

Remediation Available

dovecotDebian

Fixed in:1:2.3.13+dfsg1-2+deb11u4CVE-2026-40020

Fixed in:1:2.3.19.1+dfsg1-2.1+deb12u6CVE-2026-40020

Fixed in:1:2.4.1+dfsg1-6+deb13u6CVE-2026-40020

Fixed in:1:2.4.4+dfsg1-1CVE-2026-40020

dovecotUbuntu

Fixed in:1:2.3.16+dfsg1-3ubuntu2.9USN-8365-1

Fixed in:1:2.3.21+dfsg1-2ubuntu6.5USN-8365-1

Fixed in:1:2.4.1+dfsg1-5ubuntu4.2USN-8365-1

dovecot-coreUbuntu

Fixed in:1:2.3.16+dfsg1-3ubuntu2.9USN-8365-1

Fixed in:1:2.3.21+dfsg1-2ubuntu6.5USN-8365-1

Fixed in:1:2.4.1+dfsg1-5ubuntu4.2USN-8365-1

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 ComplexityHigh

Privileges RequiredLow

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityNone

IntegrityNone

AvailabilityLow

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

Exploit Intelligence

0.27%probability of exploitation in 30 days

19thpercentile

Low risk: more likely to be exploited than 19% of all known CVEs.

References

Vendor Advisory1

documentation.open-xchange.com

Related Vulnerabilities

Other CWE-284 (Improper Access Control) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2023-27350	Critical	9.8	100%	KEV + Ransom	Fix
CVE-2019-1653	High	7.5	100%	KEV	-
CVE-2023-23752	Medium	5.3	100%	KEV	Fix
CVE-2023-29298	High	7.5	100%	KEV	-
CVE-2023-38205	High	7.5	100%	KEV	-
CVE-2024-27348	Critical	9.8	99%	KEV	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 2026-05-18.