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OX Dovecot CVE-2026-40014

| EUVDEUVD-2026-67664 MEDIUM
Uncontrolled Resource Consumption (CWE-400)
2026-08-28 OX GHSA-r364-r477-7mhc
Denial Of Service Ox Dovecot Pro Ox Dovecot Ce
6.5
CVSS 3.1 · Vendor: OX
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Severity by source

Vendor (OX) PRIMARY
6.5 MEDIUM
AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
vuln.today AI
6.5 MEDIUM

Network delivery with no server-side auth needed; UI:R because THREAD command must be issued by client; purely availability impact.

3.1 AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
4.0 AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

Primary rating from Vendor (OX).

CVSS VectorVendor: OX

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

Lifecycle Timeline

2
Patch available
Aug 28, 2026 - 13:17 EUVD
Analysis Generated
Aug 28, 2026 - 12:11 vuln.today

DescriptionCVE.org

An attacker that can send mail to a user can craft a message header that makes the IMAP THREAD command consume CPU disproportionate to the size of the message. When a mail client issues a THREAD command on the affected mailbox, this can cause degradation or denial of service for IMAP. Monitor system for abnormal CPU usage, kill the offending process and remove the offending message from the affected mailbox. Update to non-vulnerable version. No publicly available exploits are known.

AnalysisAI

CPU exhaustion in OX Dovecot's IMAP THREAD command allows a remote unauthenticated attacker to degrade or deny IMAP service by sending a specially crafted message header to any mailbox user. The vulnerability triggers when a mail client subsequently issues a THREAD command on the affected mailbox, causing disproportionate CPU consumption relative to message size. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

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Delivery
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Vulnerability AssessmentAI

Exploitation The attacker must be able to deliver email to the target user's mailbox - no authentication to the Dovecot server itself is required (PR:N per CVSS). … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment The CVSS 3.1 score of 6.5 (AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H) accurately reflects the attack profile: network-accessible, low complexity, no authentication, but requiring user interaction in the form of a mail client issuing a THREAD command. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario Full exploit scenario with step-by-step reproduction available after sign-in.
Remediation The vendor recommends updating to a non-vulnerable version; consult the Open-Xchange security advisory at https://documentation.open-xchange.com/dovecot/security/advisories/csaf/2026/oxdc-adv-2026-0003.json for the specific patched release, as no exact fix version was enumerated in the available intelligence. … Detailed patch versions, workarounds, and compensating controls in full report.
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CVE-2026-40014 vulnerability details – vuln.today
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