Bug 2559194

Summary:	CVE-2026-79611 xen: xen: Denial of Service of guest virtual machines via VM entry failure [fedora-all]
Product:	[Fedora] Fedora	Reporter:	Oleg Sushchenko <osushche>
Component:	xen	Assignee:	Michael Young <m.a.young>
Status:	ON_QA ---	QA Contact:	Fedora Extras Quality Assurance <extras-qa>
Severity:	medium	Docs Contact:
Priority:	medium
Version:	rawhide	CC:	jforbes, m.a.young
Target Milestone:	---	Keywords:	Security, SecurityTracking
Target Release:	---
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:	{"flaws": ["a4cb6ead-fd21-4847-8965-c132a423b75c"]}
Fixed In Version:		Doc Type:	---
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:		Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:
Bug Blocks:	2550652

Description Oleg Sushchenko 2026-10-22 17:37:11 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.

For XSA-308 logic was introduced, as VMX VMEntry checks do not like the
exact combination of state which occurs when #DB in intercepted, Single
Stepping is active, and blocked by STI/MovSS is active, despite this being
a legitimate state to be in.  The resulting VMEntry failure is fatal to
the guest.

Sadly there is another special sub-case of the above, with branch tracing
enabled.  In that case the prior adjustment would still cause a VMentry
failure, as before fatal to the guest.

Comment 1 Fedora Update System 2026-10-30 23:27:47 UTC

FEDORA-2026-2b73a60d2c (xen-4.20.4-4.fc43) has been submitted as an update to Fedora 43.
https://bodhi.fedoraproject.org/updates/FEDORA-2026-2b73a60d2c

Comment 2 Fedora Update System 2026-10-31 02:44:27 UTC

FEDORA-2026-2b73a60d2c 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-2026-2b73a60d2c`
You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2026-2b73a60d2c

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

Comment 3 Fedora Update System 2026-11-06 03:33:47 UTC

FEDORA-2026-94fa41e927 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-2026-94fa41e927`
You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2026-94fa41e927

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