Bug 2526675 - CVE-2026-40017 dovecot: Dovecot: Denial of Service via crafted IMAP message headers [fedora-all]
Summary: CVE-2026-40017 dovecot: Dovecot: Denial of Service via crafted IMAP message h...
Keywords:
Status: ON_QA
Alias: None
Product: Fedora
Classification: Fedora
Component: dovecot
Version: rawhide
Hardware: Unspecified
OS: Unspecified
medium
medium
Target Milestone: ---
Assignee: Michal Hlavinka
QA Contact: Fedora Extras Quality Assurance
URL:
Whiteboard: {"flaws": ["a05599c8-068d-4883-a5fd-1...
Depends On:
Blocks: CVE-2026-40017
TreeView+ depends on / blocked
 
Reported: 2026-09-01 07:25 UTC by Vladimir Vasilev
Modified: 2026-09-11 02:27 UTC (History)
3 users (show)

Fixed In Version:
Clone Of:
Environment:
Last Closed:
Type: ---
Embargoed:


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Description Vladimir Vasilev 2026-09-01 07:25:38 UTC
Disclaimer: Community trackers are created by Red Hat Product Security team on a best effort basis. Package maintainers are required to ascertain if the flaw indeed affects their package, before starting the update process.

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.

Comment 1 Fedora Update System 2026-09-10 05:35:51 UTC
FEDORA-2026-e8a6485109 (dovecot-2.4.5-1.fc43) has been submitted as an update to Fedora 43.
https://bodhi.fedoraproject.org/updates/FEDORA-2026-e8a6485109

Comment 2 Fedora Update System 2026-09-11 01:34:35 UTC
FEDORA-2026-8b8efbd2b8 has been pushed to the Fedora 45 testing repository.
Soon you'll be able to install the update with the following command:
`sudo dnf upgrade --enablerepo=updates-testing --refresh --advisory=FEDORA-2026-8b8efbd2b8`
You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2026-8b8efbd2b8

See also https://fedoraproject.org/wiki/QA:Updates_Testing for more information on how to test updates.

Comment 3 Fedora Update System 2026-09-11 02:07:24 UTC
FEDORA-2026-e8a6485109 has been pushed to the Fedora 43 testing repository.
Soon you'll be able to install the update with the following command:
`sudo dnf upgrade --enablerepo=updates-testing --refresh --advisory=FEDORA-2026-e8a6485109`
You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2026-e8a6485109

See also https://fedoraproject.org/wiki/QA:Updates_Testing for more information on how to test updates.

Comment 4 Fedora Update System 2026-09-11 02:27:19 UTC
FEDORA-2026-2e6b786570 has been pushed to the Fedora 44 testing repository.
Soon you'll be able to install the update with the following command:
`sudo dnf upgrade --enablerepo=updates-testing --refresh --advisory=FEDORA-2026-2e6b786570`
You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2026-2e6b786570

See also https://fedoraproject.org/wiki/QA:Updates_Testing for more information on how to test updates.


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