Platform
other
Component
ox-dovecot-pro
Fixed in
2.3.1
CVE-2026-27856 describes a timing oracle vulnerability within OX Dovecot Pro, specifically concerning the verification of doveadm credentials. This flaw allows an attacker to potentially determine the configured credentials through timing analysis, leading to full access to the affected component. The vulnerability impacts versions 0 through 2.3.0, and a fix is available; upgrading is the recommended remediation.
The core of this vulnerability lies in the direct comparison of credentials used by the doveadm utility within OX Dovecot Pro. This direct comparison is susceptible to a timing oracle attack. An attacker can exploit this by repeatedly attempting to guess credentials, observing the response times to infer the correct password. Successfully determining the credentials grants the attacker complete access to the Dovecot Pro component, potentially enabling unauthorized access to mailboxes, configuration changes, and other sensitive data. The impact is significant, as compromised credentials can lead to a complete takeover of the affected system.
CVE-2026-27856 was publicly disclosed on 2026-03-27. As of the current date, no publicly available proof-of-concept (PoC) exploits have been released. The vulnerability is not currently listed on CISA KEV. The probability of exploitation is considered low to medium, given the technical nature of the attack and the absence of readily available exploits, but proactive mitigation is still recommended.
Exploit Status
EPSS
0.04% (12% percentile)
CISA SSVC
CVSS Vector
The primary mitigation for CVE-2026-27856 is to upgrade to a patched version of OX Dovecot Pro. Until an upgrade is possible, immediate steps should be taken to limit the attack surface. Restricting access to the doveadm HTTP service port (typically port 8000) is crucial, allowing only authorized personnel to connect. Consider implementing a Web Application Firewall (WAF) with rules to detect and block suspicious requests targeting the doveadm endpoint. While no public exploits are known, proactive security measures are essential to prevent potential exploitation.
Update OX Dovecot Pro to a version later than 2.3.0. Limit access to the doveadm http service port to mitigate the risk while updating.
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CVE-2026-27856 is a HIGH severity vulnerability in OX Dovecot Pro versions 0–2.3.0 where direct credential comparison allows timing oracle attacks, potentially revealing credentials.
If you are using OX Dovecot Pro versions 0 through 2.3.0 and the doveadm service is accessible, you are potentially affected by this vulnerability.
Upgrade to a patched version of OX Dovecot Pro. As an interim measure, restrict access to the doveadm HTTP service port (8000).
As of the current date, no active exploitation of CVE-2026-27856 has been confirmed, but proactive mitigation is recommended.
Refer to the official OX Dovecot Pro security advisories on their website for detailed information and updates regarding CVE-2026-27856.
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