CVE-2026-27856
Received Received - Intake
Timing Oracle Vulnerability in Doveadm Enables Credential Disclosure

Publication date: 2026-03-27

Last updated on: 2026-04-29

Assigner: Open-Xchange

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.
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Meta Information
Published
2026-03-27
Last Modified
2026-04-29
Generated
2026-06-16
AI Q&A
2026-03-27
EPSS Evaluated
2026-06-15
NVD
CVE-2026-27856
EUVD
EUVD-2026-16565
Affected Vendors & Products
Showing 4 associated CPEs
Vendor Product Version / Range
dovecot dovecot to 2.4.3 (exc)
open-xchange dovecot From 3.0.0 (inc) to 3.0.5 (exc)
open-xchange dovecot From 3.1.0 (inc) to 3.1.4 (exc)
open-xchange dovecot to 2.3.22.1 (exc)
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-287 When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct.
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Executive Summary

This vulnerability involves the Doveadm component verifying credentials using a direct comparison method that is vulnerable to a timing oracle attack.

An attacker can exploit this timing difference to determine the configured credentials.

Once the attacker figures out the credentials, they can gain full access to the affected component.

Impact Analysis

If exploited, this vulnerability can allow an attacker to obtain the credentials for the Doveadm component.

With these credentials, the attacker can gain full access to the affected component, potentially compromising the system.

This could lead to unauthorized access and control over the services provided by Doveadm.

Detection Guidance

This vulnerability involves a timing oracle attack on doveadm credentials due to direct comparison verification. Detection would involve monitoring access attempts to the doveadm HTTP service port and analyzing for unusual timing patterns or repeated authentication attempts that could indicate exploitation attempts.

Since no publicly available exploits are known and no specific detection commands are provided, general network monitoring and logging of access to the doveadm HTTP service port is recommended.

Mitigation Strategies
  • Limit access to the doveadm HTTP service port to trusted hosts only.
  • Install the fixed version of the software that addresses this vulnerability.
Compliance Impact

The vulnerability allows an attacker to determine configured credentials through a timing oracle attack, potentially leading to full access to the affected component. This unauthorized access could result in exposure or compromise of sensitive data.

Such unauthorized access and potential data compromise may negatively impact compliance with standards and regulations like GDPR and HIPAA, which require protection of personal and sensitive information.

Mitigation steps include limiting access to the doveadm HTTP service port and installing a fixed version, which are necessary to maintain compliance and reduce risk.

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