CVE-2026-40017
Description
An attacker that can send mail to a user can craft a message header whose values are chosen to collide in an internal hash table, which makes the IMAP THREAD command consume CPU disproportionate to the size of the message. This is a separate issue from CVE-2026-40014 and is not addressed by that fix. Whenever 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.
How to fix
- Open-Xchange GmbH OX Dovecot Pro2.3.22.2, 3.0.7, 3.1.6 or later
- Open-Xchange GmbH OX Dovecot CE2.4.5 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| Open-Xchange GmbH OX Dovecot Pro | 2.3.0 ≤ v < 2.3.22.2, 3.0.0 ≤ v < 3.0.7, 3.1.0 ≤ v < 3.1.6 | 2.3.22.2, 3.0.7, 3.1.6 |
| Open-Xchange GmbH OX Dovecot CE | 2.3.0 ≤ v < 2.4.5 | 2.4.5 |
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