Bug 2506178 - CVE-2026-40691 unbound: Unbound: Denial of Service via crafted DNSCrypt query [fedora-all]
Summary: CVE-2026-40691 unbound: Unbound: Denial of Service via crafted DNSCrypt query...
Keywords:
Status: CLOSED ERRATA
Alias: None
Product: Fedora
Classification: Fedora
Component: unbound
Version: rawhide
Hardware: Unspecified
OS: Unspecified
high
high
Target Milestone: ---
Assignee: Paul Wouters
QA Contact: Fedora Extras Quality Assurance
URL:
Whiteboard: {"flaws": ["81123d51-1539-4276-bd43-4...
Depends On:
Blocks: CVE-2026-40691
TreeView+ depends on / blocked
 
Reported: 2026-07-22 16:15 UTC by Marco Benatto
Modified: 2026-07-31 01:14 UTC (History)
6 users (show)

Fixed In Version: unbound-1.25.2-1.fc44 unbound-1.25.2-1.fc43
Clone Of:
Environment:
Last Closed: 2026-07-30 01:16:48 UTC
Type: ---
Embargoed:


Attachments (Terms of Use)

Description Marco Benatto 2026-07-22 16:15:49 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.

A denial of service vulnerability has been discovered in Unbound when compiled with DNSCrypt support ('--enable-dnscrypt').
A single bad DNSCrypt query over TCP could underflow Unbound's DNSCrypt packet reading procedure that may lead to heap overflow and eventual server crash and denial of service.

Unbound 1.25.2 includes fixes to select the proper buffer TCP buffer for DNSCrypt, to properly check against the buffer's capacity and to clear the buffer before writing the dnscrypt contents otherwise UDP queries can hit assertions.

Comment 1 Fedora Update System 2026-07-27 10:29:15 UTC
FEDORA-2026-e495bd59ef (unbound-1.25.2-1.fc44) has been submitted as an update to Fedora 44.
https://bodhi.fedoraproject.org/updates/FEDORA-2026-e495bd59ef

Comment 2 Fedora Update System 2026-07-27 10:34:04 UTC
FEDORA-2026-3170ee6a1c (unbound-1.25.2-1.fc43) has been submitted as an update to Fedora 43.
https://bodhi.fedoraproject.org/updates/FEDORA-2026-3170ee6a1c

Comment 3 Fedora Update System 2026-07-28 01:35:42 UTC
FEDORA-2026-e495bd59ef 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-e495bd59ef`
You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2026-e495bd59ef

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

Comment 4 Fedora Update System 2026-07-28 01:57:16 UTC
FEDORA-2026-3170ee6a1c 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-2026-3170ee6a1c`
You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2026-3170ee6a1c

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

Comment 5 Fedora Update System 2026-07-30 01:16:48 UTC
FEDORA-2026-e495bd59ef (unbound-1.25.2-1.fc44) has been pushed to the Fedora 44 stable repository.
If problem still persists, please make note of it in this bug report.

Comment 6 Fedora Update System 2026-07-31 01:14:34 UTC
FEDORA-2026-3170ee6a1c (unbound-1.25.2-1.fc43) has been pushed to the Fedora 43 stable repository.
If problem still persists, please make note of it in this bug report.


Note You need to log in before you can comment on or make changes to this bug.