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    CVE-2026-27856

    Doveadm credentials are verified using direct comparison which is susceptible to timing oracle attack. An attacker can use this to determine the configured credentials. Figuring out the credential will lead into full access to the affected component. Limit access to the doveadm http service port, install fixed version. No publicly available exploits are known.

    Published:Mar 27, 2026
    Last Modified:Apr 29, 2026
    EPS:Mar 27, 2026
    EPSS Score:0.00043
    CVSS Score:7.4

    Affected Products

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

    Exploits

    No exploit reference

    Related CVEs

    CVE-2026-42006 (CVSS 4.3) — An attacker can cause uncontrolled memory usage with excessive bracing over IMAP. The fix in CVE-2026-27857 wa…
    CVE-2026-40020 (CVSS 3.1) — Attacker can use the IMAP SETACL command to inject the anyone permission to user's dovecot-acl file even if im…
    CVE-2026-40016 (CVSS 5.3) — Attacker can upload a malicious Sieve script over ManageSieve service (or locally) to bypass configured CPU ti…
    CVE-2026-33603 (CVSS 6.8) — Attacker can use a specially crafted base64 exchange between Dovecot and Client to fake SCRAM TLS channel bind…
    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-2026-27855 (CVSS 6.8) — Dovecot OTP authentication is vulnerable to replay attack under specific conditions. If auth cache is enabled,…

    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