CVE-2026-40017: Uncontrolled Resource Consumption in Open-Xchange GmbH OX Dovecot Pro
Description
CVE-2026-40017 is a vulnerability in Open-Xchange GmbH OX Dovecot Pro where an attacker who can send mail to a user crafts message headers that cause excessive CPU consumption during IMAP THREAD command processing. This leads to potential denial of service or performance degradation when the THREAD command is issued on the affected mailbox. The issue is distinct from CVE-2026-40014 and is not fixed by that update. No public exploits are known. Monitoring for abnormal CPU usage and removing offending messages can mitigate impact until an update is applied.
CVSS v3.1
Score 6.5medium
Affected software
Open-Xchange GmbH
OX Dovecot Pro
Open-Xchange GmbH
OX Dovecot CE
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
This vulnerability involves uncontrolled resource consumption in OX Dovecot Pro's IMAP THREAD command. An attacker sending a specially crafted email with header values designed to collide in an internal hash table causes the THREAD command to consume disproportionate CPU resources relative to message size. This can degrade or deny IMAP service for the mailbox. The flaw is separate from CVE-2026-40014 and requires a different fix. No known public exploits exist. The vulnerability affects specific versions of OX Dovecot Pro.
Potential Impact
The vulnerability can cause high CPU usage leading to degradation or denial of IMAP service when a mail client issues the THREAD command on a mailbox containing the crafted message. There is no impact on confidentiality or integrity, only availability is affected. No public exploits are known, so exploitation risk is currently theoretical but could lead to denial of service conditions.
Mitigation Recommendations
No official patch or remediation level is stated in the available data. Users should monitor systems for abnormal CPU usage related to IMAP THREAD commands, terminate offending processes, and remove malicious messages from mailboxes. Updating to a non-vulnerable version is recommended once available. Patch status is not yet confirmed — check the vendor advisory for current remediation guidance.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- OX
- Date Reserved
- 2026-04-08T09:59:59.342Z
- Cvss Version
- 3.1
- State
- PUBLISHED
Threat ID: 6a916f8aacd9273b49cf9201
Added to database: 08/28/2026, 11:22:50 UTC
Last enriched: 09/10/2026, 02:53:02 UTC
Last updated: 10/13/2026, 06:48:16 UTC
Views: 29
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