---
id: CVE-2026-79611
title: |-
  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…
summary: |-
  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…
severity: medium
published: '2026-10-13'
updated: '2026-10-14'
sourceUpdated: '2026-10-14T16:10:14.750'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-79611'
references:
  - url: 'https://xenbits.xenproject.org/xsa/advisory-518.html'
    label: security@xen.org
  - url: 'http://www.openwall.com/lists/oss-security/2026/10/13/7'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'http://xenbits.xen.org/xsa/advisory-518.html'
    label: af854a3a-2127-422b-91ae-364da2661108
tags:
  - nvd
  - cve.org
ingestedAt: '2026-10-13T16:35:46.745Z'
vendor: Xen
product: Xen
affected:
  - Xen
epss: 0.00161
epssPercentile: 0.05199
cvss: 5.5
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-10-20T17:31:36.841344Z'
cvssSource: adp
---

## Overview

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.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.