What’s Vulnerable › Vulnerabilities

CVE-2026-27856

• Severity: medium (CVSS 5.9 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-03-27 · updated 2026-10-26
• Weakness: CWE-287

Description

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.

Affected products

• dovecot: before 2.4.3 — fixed in 2.4.3
• Open-Xchange Dovecot: before 2.3.22.1; from 3.0.0 before 3.0.5; from 3.1.0 before 3.1.4 — fixed in 2.3.22.1, 3.0.5, 3.1.4

How to fix

Upgrade to a fixed version: dovecot 2.4.3; Open-Xchange Dovecot 2.3.22.1, 3.0.5, 3.1.4. Check the vendor advisory for mitigations.

References

• https://documentation.open-xchange.com/dovecot/security/advisories/csaf/2026/oxdc-adv-2026-0001.json
• https://access.redhat.com/errata/RHSA-2026:26564
• https://access.redhat.com/security/cve/CVE-2026-27856
• https://bugzilla.redhat.com/show_bug.cgi?id=2452171
• https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-27856.json

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