CVE-2026-40017 Affecting dovecot package, versions <1:2.4.5+dfsg1-1


Severity

Recommended
low

Based on default assessment until relevant scores are available.

Threat Intelligence

EPSS
0.27% (20th percentile)

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  • Snyk IDSNYK-DEBIANUNSTABLE-DOVECOT-19424906
  • published29 Aug 2026
  • disclosed28 Aug 2026

Introduced: 28 Aug 2026

NewCVE-2026-40017  (opens in a new tab)

How to fix?

Upgrade Debian:unstable dovecot to version 1:2.4.5+dfsg1-1 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream dovecot package and not the dovecot package as distributed by Debian. See How to fix? for Debian:unstable relevant fixed versions and status.

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.

CVSS Base Scores

version 3.1