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Xen: 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… (CVE-2026-79611)

0
Medium
VulnerabilityCVE-2026-79611gcveosvubuntu-cve-2026-79611cve-2026-79611ubuntu-16-04-ltsubuntu-18-04-ltsubuntu-20-04-ltsubuntu-22-04-ltsubuntu-24-04-ltsubuntu-26-10ubuntu-26-04-lts
Published: 10/15/2026 (10/15/2026, 00:00:00 UTC)
Source: GCVE Database
Product: xen

Description

A vulnerability in Xen hypervisor causes a fatal VMEntry failure to guest virtual machines when certain processor states coincide, specifically when debug exceptions (#DB) are intercepted, single stepping is active, and STI/MovSS blocking is enabled. An additional sub-case involving branch tracing also triggers this failure. This issue results in guest crashes but does not impact confidentiality or integrity.

CVSS v3.1

Score 5.5medium

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Affected software

Ubuntu:16.04:LTSmore threats →ghsa
xen
pkg:deb/ubuntu/xen?arch=source&distro=xenial
Affected versions
=4.5.1-0ubuntu1=4.5.1-0ubuntu2=4.6.0-1ubuntu1=4.6.0-1ubuntu2=4.6.0-1ubuntu4=4.6.0-1ubuntu4.1=4.6.0-1ubuntu4.2=4.6.0-1ubuntu4.3=4.6.5-0ubuntu1=4.6.5-0ubuntu1.1=4.6.5-0ubuntu1.2=4.6.5-0ubuntu1.4
Ubuntu:18.04:LTSmore threats →ghsa
xen
pkg:deb/ubuntu/xen?arch=source&distro=bionic
Affected versions
=4.9.0-0ubuntu3=4.9.0-0ubuntu4=4.9.2-0ubuntu1
Ubuntu:20.04:LTSmore threats →ghsa
xen
pkg:deb/ubuntu/xen?arch=source&distro=focal
Affected versions
=4.9.2-0ubuntu2=4.9.2-0ubuntu6=4.9.2-0ubuntu7=4.11.3+24-g14b62ab3e5-1ubuntu1=4.11.3+24-g14b62ab3e5-1ubuntu2=4.11.3+24-g14b62ab3e5-1ubuntu2.2=4.11.3+24-g14b62ab3e5-1ubuntu2.3
Ubuntu:22.04:LTSmore threats →ghsa
xen
pkg:deb/ubuntu/xen?arch=source&distro=jammy
Affected versions
=4.11.4+24-gddaaccbbab-1ubuntu2=4.16.0-1~ubuntu2=4.16.0-1~ubuntu2.1
Ubuntu:24.04:LTSmore threats →ghsa
xen
pkg:deb/ubuntu/xen?arch=source&distro=noble
Affected versions
=4.17.2-1=4.17.2+55-g0b56bed864-1=4.17.2+76-ge1f9cb16e2-1=4.17.2+76-ge1f9cb16e2-1ubuntu1=4.17.3+10-g091466ba55-1=4.17.3+10-g091466ba55-1.1ubuntu2=4.17.3+10-g091466ba55-1.1ubuntu3
Ubuntu:26.10more threats →ghsa
xen
pkg:deb/ubuntu/xen?arch=source&distro=stonking
Affected versions
=4.20.2+7-g1badcf5035-2build2=4.20.2+37-g61ff35323e-1ubuntu1=4.20.3+127-gc42374a105-1
Ubuntu:26.04:LTSmore threats →ghsa
xen
pkg:deb/ubuntu/xen?arch=source&distro=resolute
Affected versions
=4.20.0+68-g35cb38b222-1=4.20.2+7-g1badcf5035-2=4.20.2+7-g1badcf5035-2build2

Run on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.

AI-Powered Analysis

Machine-generated threat intelligence

AILast updated: 10/22/2026, 17:41:03 UTC

Technical Analysis

CVE-2026-79611 describes a Xen hypervisor vulnerability where VMX VMEntry checks fail due to an exact combination of processor states: intercepted debug exceptions (#DB), active single stepping, and STI/MovSS blocking. This legitimate processor state combination causes VMEntry failures that are fatal to the guest VM. A further sub-case with branch tracing enabled also leads to the same fatal VMEntry failure. The vulnerability causes denial of service to guest virtual machines by crashing them during VM entry.

Potential Impact

The vulnerability leads to denial of service by causing fatal VMEntry failures that crash guest virtual machines. There is no impact on confidentiality or integrity of data. The issue affects the availability of guest VMs running on affected Xen versions.

Mitigation Recommendations

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until a fix is available, avoid configurations that trigger the specific processor state combinations if possible. Monitor vendor channels for updates and apply official patches once released.

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Technical Details

Gcve Source
db.gcve.eu
Osv Id
UBUNTU-CVE-2026-79611
Osv Schema Version
1.7.0
Ecosystems
["Ubuntu:16.04:LTS","Ubuntu:18.04:LTS","Ubuntu:20.04:LTS","Ubuntu:22.04:LTS","Ubuntu:24.04:LTS","Ubuntu:26.10","Ubuntu:26.04:LTS"]
Cvss Version
3.1

Threat ID: 6ada45094d27ba8daa6a5b36

Added to database: 10/22/2026, 17:16:57 UTC

Last enriched: 10/22/2026, 17:41:03 UTC

Last updated: 10/22/2026, 17:41:03 UTC

Views: 4

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