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    CVE-2026-40020

    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.

    Published:May 12, 2026
    Last Modified:May 18, 2026
    EPS:May 12, 2026
    EPSS Score:0.00013
    CVSS Score:3.1

    Affected Products

    Vendor
    Dovecot
    Product
    Dovecot
    Vendor
    Open-xchange
    Product
    Dovecot
    Vendor
    Open-xchange
    Product
    Ox Dovecot Pro

    Exploits

    No exploit reference

    Common Weakness Enumeration

    CWE-284 Improper Access Control

    Related CVEs

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    CVE-2026-27851 (CVSS 7.4) — When safe filter is used with variable expansion, all following pipelines on the same string are incorrectly i…
    CVE-2026-27860 (CVSS 3.7) — If auth_username_chars is empty, it is possible to inject arbitrary LDAP filter to Dovecot's LDAP authenticati…
    CVE-2026-27859 (CVSS 5.3) — A mail message containing excessive amount of RFC 2231 MIME parameters causes LMTP to use too much CPU. A suit…
    CVE-2026-27858 (CVSS 7.5) — Attacker can send a specifically crafted message before authentication that causes managesieve to allocate lar…
    CVE-2026-27857 (CVSS 4.3) — Sending "NOOP (((...)))" command with 4000 parenthesis open+close results in ~1MB extra memory usage. Longer c…
    CVE-2026-27856 (CVSS 7.4) — Doveadm credentials are verified using direct comparison which is susceptible to timing oracle attack. An atta…
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    Common Vulnerability Scoring System

    Attack Vector
    Network
    Adjacent
    Local
    Physical
    Privileges Required
    None
    Low
    High
    User Interaction
    None
    Required
    Scope
    Unchanged
    Changed
    Confidentiality
    None
    Low
    High
    Integrity
    None
    Low
    High
    Availability
    None
    Low
    High