CVE-2026-40020

Severity: medium (CVSS 4.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-05-12 · updated 2026-10-26
Weakness: CWE-284

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.

Affected products

dovecot: before 2.4.4 — fixed in 2.4.4
Open-Xchange Dovecot: before 3.1.5 — fixed in 3.1.5

How to fix

Upgrade to a fixed version: dovecot 2.4.4; Open-Xchange Dovecot 3.1.5. Check the vendor advisory for mitigations.

References

https://documentation.open-xchange.com/dovecot/security/advisories/csaf/2026/oxdc-adv-2026-0002.json

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